Prenatal care

Prenatal care is the health care provided throughout a pregnancy; it is aimed at optimizing maternal and fetal outcomes. Prenatal visits allow high-risk pregnancies to be identified and are used to monitor maternal health and fetal development. After an initial visit (usually in the first trimester), follow-up prenatal visits generally occur once monthly until 28 weeks' gestation, twice monthly between 28 and 36 weeks, and weekly after 36 weeks. Components of prenatal visits include evaluation of the medical history, physical and gynecological examinations, laboratory testing, and ultrasonography. More frequent assessment may be indicated in pregnancies deemed high-risk for the fetus or pregnant individual. This article covers the general principles of prenatal care, including recommended screening studies, elective prenatal genetic screening, fetal surveillance, and patient education.

For other aspects of peripartum care, see also “Preconception counseling,” “Normal labor and delivery,” “Abnormal labor and delivery,” and “Postpartum visit.” For prenatal care for transgender and nonbinary individuals, see “Pregnancy in transgender individuals.”

Diagnosis of pregnancy is covered in “Pregnancy.”

Ethics of prenatal care ^[1][2]

• Healthcare providers have an ethical obligation to obtain informed consent from patients for prenatal care.
• Patients may refuse recommended screening or procedures.
• Use shared-decision making when discussing treatment options with patients in order to:
  • Ensure a safe environment for asking questions and addressing concerns
  • Encourage voluntary, informed decisions
  • Avoid miscommunication

Because pregnancy outcomes are unpredictable, pregnant individuals should be informed about the potential need for obstetric interventions (e.g., cesarean delivery) and encouraged to discuss any concerns ahead of time. ^[1]

Legal aspects of prenatal care

• Follow state laws pertaining to induced abortion and mandatory reporting (e.g., of maternal substance use). ^[3]
• Regardless of state law, EMTALA allows for provision of emergency abortion to stabilize a patient. ^[4]
• In accordance with EMTALA, patients in active labor cannot be turned away.
• See also “Principles of medical law and ethics.”

Frequency of prenatal visits ^[1]

• Visit frequency should be tailored to maternal needs and pregnancy risk factors. ^[1][5]
• Typical timing of routine prenatal visits for an uncomplicated pregnancy:
  • Initial visit: usually in the first trimester ^[5]
  • Follow-up visits ^[1]
    • Every 4 weeks: from initial visit to 28 weeks' gestation
    • Every 2 weeks: from 28 to 36 weeks' gestation
    • Weekly: from 36 weeks' gestation until delivery (see also “Postterm pregnancy”)

High-risk pregnancies generally warrant more than the usual number of follow-up visits for maternal and/or fetal surveillance. ^[1]

Monitoring fetal growth and wellbeing

General principles ^[6][7]

• Assess growth via physical examinations and ultrasound (US).
• In high-risk pregnancies or if there is concern for fetal well-being, consider:
  • Specialized ultrasound
  • Antepartum fetal surveillance

Gestational age and estimated date of delivery ^[1][8]

• Determination of gestational age and estimated date of delivery is important for:
  • Guiding the timing of prenatal screening and fetal monitoring
  • Managing postterm pregnancy
• Methods of pregnancy dating include one or both of the following:
  • Naegele rule
    • Expected date of delivery (due date) is estimated as the first day of the LMP + 280 days ^[8][9]
    • May be unreliable in patients with uncertain LMP or irregular menstrual cycles
  • Ultrasound: should be performed to estimate gestational age if LMP is unreliable. ^[1][10]
    • First-trimester US: estimation is based on crown-rump length
    • Second-trimester US: estimation is based on fetal biometric parameters
• For a gestational age discrepancy between ultrasound and LMP, use EDD determined by ultrasound if: ^[8]
  • > 5 days gestational age discrepancy in gestations < 9 weeks
  • > 7 days gestational age discrepancy in gestations 9–13 weeks

Symphysis-fundal height measurement ^[6]

• Measured from the top of the pubic symphysis to the top of the uterus.
• Fundal height can be used to monitor fetal growth or to roughly estimate gestational age in an emergency. ^[11]
• Screen all patients > 24 weeks' gestation for fetal growth abnormalities using symphysis fundal height. ^[6]
• From 20 weeks, fundal height in centimeters should roughly approximate the week of gestation. ^[12]
• If comparison of fundal height and gestational age suggests growth abnormality , perform an ultrasound. ^[10]

Prenatal ultrasound

Standard examinations ^[10]

• First-trimester US is performed to estimate gestational age and assess for complications (e.g., suspected ectopic pregnancy).
• A second-trimester US is recommended between 18–22 weeks to assess fetal anatomy.
• For more information, see “First-trimester ultrasound” and “Second-trimester ultrasound.”

Additional ultrasounds ^[10][14]

Additional US may be performed for further evaluation of potential pregnancy complications, follow-up of abnormal US, and for imaging guidance during procedures.

• US-guided procedures
  • Genetic testing: guided needle placement in amniocentesis or chorionic villus sampling
  • Cervical cerclage placement: in cervical insufficiency
  • External cephalic version: to turn a breech baby before labor
• Limited US: imaging of a specific area based on clinical concern
• Specialized US: detailed US evaluation performed to further evaluate for fetal abnormalities in patients with concerning findings on clinical history and/or examination, laboratory testing, and/or prior ultrasound examination
  • Nuchal translucency: as part of prenatal genetic testing
  • Fetal echocardiography: in suspected congenital heart disease ^[15]
  • Biophysical profile: if there is concern for fetal well-being
  • Transvaginal measurement of cervical length: if there are concerns for preterm labor
  • Doppler ultrasound; : for suspected abnormalities in fetal/placental perfusion or suspected fetal deformities ^[16][17]

High-risk pregnancies ^[1][19][21]

• Early identification and management of high-risk pregnancies is essential for the prevention and treatment of associated maternal and fetal complications.
• Assess for risk factors for adverse pregnancy outcomes at each visit.

Risk factors for adverse pregnancy outcomes ^[1][19]

• Maternal factors ^[22]
  • Advanced maternal age
  • Preexisting medical conditions
  • Preexisting gynecological conditions
  • Risk factors for hypertensive pregnancy disorders
  • Substance use, including tobacco and alcohol
• Fetal-placental factors
  • Multiple gestation
  • Fetal structural or genetic abnormalities
  • Placental abnormalities (e.g., placenta accreta, placenta previa)
  • Placental abruption
  • Vasa previa
  • Abnormal amniotic fluid levels (e.g., oligohydramnios, polyhydramnios)
• Pregnancy-related factors
  • Prior complicated pregnancies, e.g.:
    • Stillbirth
    • Preterm birth, preterm premature rupture of membranes, or infant with low birth weight
    • Previous infant with anatomic or genetic abnormalities
    • Cervical insufficiency
  • Pregnancy through in vitro fertilization
  • Maternal complications during pregnancy
  • Rhesus incompatibility
  • Postterm pregnancy

Management of high-risk pregnancies

• Refer patients with high-risk pregnancies to specialists as indicated, e.g.:
  • Maternal-fetal medicine
  • Pediatric specialists
• Consider increased monitoring of maternal and fetal well-being with:
  • Clinical evaluation
  • Antepartum fetal surveillance
  • Prenatal ultrasound
• Discuss the potential impacts of high-risk pregnancy with patients on:
  • Mode and timing of delivery
  • Need for postpartum and neonatal monitoring after birth
• See also “Pregnancy complications.”

General principles

• The goal of the initial prenatal visit is to determine gestational age, identify and manage risk factors, and educate patients. ^[1]
• The initial prenatal visit usually occurs in the first trimester, unless there has been late entry into prenatal care.
• Components of first-trimester care may occur prior to the initial prenatal visit.
• Some aspects of first-trimester care, e.g., prenatal genetic testing, may require multiple visits.

Initial prenatal visit ^[1][23]

• Assess patient's feelings about the pregnancy.
  • Discuss possible options if pregnancy is undesired, including:
    • Continuation of pregnancy (with plan to raise the child themselves or place the child for adoption)
    • Termination of pregnancy
  • Refer as indicated to appropriate providers, agencies, and/or support groups.
• Review prior preconception counseling, if any was given.
• Perform a comprehensive clinical assessment, including history and physical examination.
• Take a medication history; if possible, stop or change medications contraindicated in pregnancy.
• Screen for comorbid physical and mental health conditions.
• Inquire about risk factors for lead exposure and send a lead level if any are present. ^[1][24]
• Assess for risk factors for adverse pregnancy outcomes; manage as high-risk pregnancy if present.
• Determine estimated date of delivery (EDD) and perform first-trimester ultrasound, if indicated (see “Gestational age and estimated date of delivery”).
• Offer prenatal aneuploidy and genetic carrier screening (see “Prenatal genetic testing”).
• Assess vaccination status and administer vaccines recommended in pregnancy, including: ^[25]
  • Inactivated seasonal influenza vaccine
  • COVID-19 vaccine
• Provide prenatal patient education.
• Arrange follow-up visits and referrals as needed.

Live attenuated influenza, varicella, and MMR vaccine are contraindicated during pregnancy; delay administration until after delivery. ^[25]

History and physical examination ^[1][5]

• Personal medical history, including obstetric history (e.g., miscarriage, preterm delivery, preeclampsia)
• Family history: maternal and paternal ^[26]
  • Medical conditions (e.g., early-onset heart disease, cancer)
  • Genetic or congenital abnormalities
  • Poor obstetrical outcomes (e.g., preeclampsia, preterm delivery)
• Complete physical examination including: ^[1][23]
  • Height and weight ^[1][27]
  • Blood pressure to screen for hypertensive pregnancy disorders ^[28]
  • Breast examination ^[23]
  • Pelvic examination
  • Auscultation of fetal heart tones at > 10 weeks' gestation ^[23]
  • Oral health assessment

The following laboratory studies are recommended during the initial prenatal visit to screen for conditions associated with negative obstetric and fetal outcomes.

All patients

HIV screening in pregnancy is opt-out; inform individuals an HIV test will be sent as part of the routine prenatal studies unless they decline testing. ^[1]

Patients with select indications

Psychosocial assessments should be performed for all pregnant individuals in the first trimester.

Indications ^[10][14]

• Confirmation of pregnancy and its location (i.e., exclusion of ectopic pregnancy and gestational trophoblastic disease)
• Determination of EDD
• Evaluation for multiple gestation
• Assessment of fetal cardiac activity
• Evaluation of maternal symptoms (e.g., pelvic pain, vaginal bleeding) or abnormalities on examination (e.g., masses, structural uterine abnormalities)
• Evaluation of for fetal anomalies (e.g., anencephaly)
• Measurement of nuchal translucency as part of aneuploidy screening
• Provision of imaging guidance during procedures (e.g., chorionic villus sampling)

Estimating gestational age via ultrasonography is most accurate when performed in the first trimester. ^[14]

Modalities ^[10][14]

• Transvaginal ultrasound
• Transabdominal ultrasound

Components ^[10][14]

• Visualization of location and contents of gestational sac(s).
• Determination of number of fetuses.
• Evaluation of the embryo or fetus, including:
  • Cardiac activity
  • Crown-rump length for estimating gestational age ^[8]
  • Anatomy as appropriate for gestational size
  • Nuchal translucency in patients desiring aneuploidy screening
• Evaluation of maternal pelvic anatomy (e.g., uterus, adnexa, rectouterine pouch)

Approach ^[65][66]

• Offer all patients genetic carrier screening and testing for chromosomal abnormalities.
  • Screening should preferably be offered at the initial prenatal visit.
  • Provide counseling prior to prenatal genetic testing to all patients.
• For patients interested in carrier screening, see “Genetic carrier screening.”
• For patients interested in testing for chromosomal abnormalities, discuss options for both screening and diagnostic testing:
  • Noninvasive aneuploidy screening; (e.g., through measurement of maternal serum biomarkers and ultrasound; markers, or cell-free fetal DNA testing)
  • Invasive genetic testing (amniocentesis or chorionic villus sampling)
• Offer appropriate follow-up genetic counseling and/or testing depending on results.

Counseling prior to prenatal genetic testing ^[1][65][67]

• Inform patients that all prenatal genetic testing is voluntary.
• Explain the differences between screening and diagnostic testing
• Discuss the patient's risk factors for fetal genetic abnormalities.
• Discuss the benefits of early identification of disorders: ^[65]
  • Potential for prenatal treatment
  • Optimizing outcomes by referral to appropriate specialists and location for delivery
  • Possibility of pregnancy termination
• Review all testing options and associated risks and benefits.
• Use shared decision-making to decide whether to perform a test and the specific testing to perform.
• Inform patients about follow-up options for a positive test result.

Inform patients that a negative screening test result for fetal chromosomal abnormalities does not guarantee that a fetus has no genetic abnormalities. ^[68]

Risk factors associated with fetal genetic abnormalities ^[65]

• Fetal structural abnormality on ultrasound
• Increased maternal age ^[65]
• Increased paternal age
• Parental genetic abnormalities
• Previous child with aneuploidy ^[65]

Noninvasive fetal aneuploidy screening tests ^[1][66][69]

• For patients who elect to have screening for chromosomal abnormalities, select a screening test based on gestational age and patient preference. ^[66]
• Communicate results of screening tests to patients and arrange follow-up as necessary.
  • No abnormalities on screening: Inform the patient the risk of a genetic abnormality is reduced.
  • If screening results are abnormal, offer all of the following:
    • Genetic counseling
    • Invasive prenatal diagnostic testing (e.g., chorionic villus sampling, amniocentesis) ^[68]
    • Second-trimester ultrasound at 18–22 weeks' gestation

One-step screening tests

Cell-free fetal DNA testing can be performed in any trimester of pregnancy after ∼ 10 weeks' gestation. ^[66]

Multi-step screening tests

Interpretation of test results

Results of first-trimester combined screening test

On US examination of fetuses with aneuploidy, increased nuchal translucency is usually visible in the first trimester and a thickened nuchal fold is visible in the second trimester. ^[73]

Results of quad screening and triple screening

An abnormal maternal serum AFP may be due to inaccurate estimation of fetal gestational age. ^[74]

Invasive prenatal diagnostic testing ^[65]

• Invasive prenatal diagnostic testing is typically performed through chorionic villus sampling (CVS) or amniocentesis.
  • CVS is performed in the first trimester, while amniocentesis can be performed in the second or third trimester.
  • Cordocentesis to obtain a sample of fetal blood may be performed in select cases.
• Chromosomal testing of specimens collected through diagnostic procedures may include: ^[65]
  • DNA microarray
  • Karyotyping
  • Fluorescence in situ hybridization
  • Direct detection of specific DNA mutations

Routine prenatal visits in the second trimester are focused on maternal-fetal surveillance, symptom management, and prevention and management of pregnancy complications.

Components ^[1][23]

• Routine clinical assessment, including:
  • Assessment for symptoms of pregnancy complications
  • Focused physical examination
• Obstetric ultrasound for fetal anatomy screening. ^[10]
• Screening for anemia and gestational diabetes at 24–28 weeks' gestation.
• COVID-19 vaccine and inactivated influenza vaccination, if not administered earlier in pregnancy
• Prenatal counseling, including labor precautions
• Assessment for risk factors for adverse pregnancy outcomes; manage as high-risk pregnancy if present.

In uncomplicated pregnancies dated with a reliable last menstrual period, a single obstetric ultrasound may be performed, preferably at 18–22 weeks' gestation, to evaluate fetal anatomy and the EDD. ^[66][80]

Routine prenatal clinical assessment ^[1][23]

• Ask all patients about:
  • Signs of pregnancy complications (e.g., vaginal bleeding or contractions, symptoms of preeclampsia, leakage of fluid) ^[5]
  • Awareness of fetal movement ^[1][5][81]
• Perform physical examination, including:
  • Weight
  • Blood pressure to screen for hypertensive pregnancy disorders ^[28]
  • Fundal height measurement : to monitor fetal growth after 24 weeks' gestation ^[5][23]
  • Auscultation of fetal heart rate: to confirm fetal heartbeat ^[1][23]
• Consider urine dipstick analysis. ^[1][23]

Pregnant individuals often begin to feel fetal movement (i.e., quickening) between 18 and 19 weeks' gestation in the first pregnancy and between 16 and 18 weeks in subsequent pregnancies. ^[23]

In most cases, the EDD should not be changed in the second or third trimester if the EDD was established by an ultrasound performed in the first trimester. ^[8]

Laboratory studies are performed between 24–28 weeks; screening may therefore take place in the second or third trimester.

Fetal anatomy scan ^[10][14][82]

General principles

• A scan offered at 18–22 weeks' gestation to all patients to assess for:
  • Fetal anomalies, e.g., abnormal growth or anatomic abnormalities ^[10]
  • Estimation of gestational age (if not already performed) ^[10][78]
• If possible, the anatomy scan should be offered well in advance of the legal limit for pregnancy termination. ^[82]

Modalities ^[10][14]

• Transabdominal ultrasound: usually initial modality
• Transvaginal or transperineal ultrasound: if the transabdominal approach is suboptimal for evaluation

Components

• Evaluation of fetus, including:
  • Number of fetuses
  • Fetal presentation
  • Cardiac activity
  • Anatomy survey, including assessment for structural abnormalities and sex
  • Fetal biometric parameters ; ^[14]
    • Biparietal diameter
    • Fetal femoral length
    • Abdominal circumference
    • Head circumference
• Evaluation of amniotic fluid volume and placenta (e.g., location, appearance, cord insertion)
• Evaluation of maternal pelvic anatomy, including cervix ^[14][83]

Additional ultrasounds

• Indications include:
  • Provide imaging guidance during procedures (e.g., amniocentesis)
  • Evaluation of suspected fetal or maternal abnormalities
  • Potential obstetric emergencies, e.g., vaginal bleeding or premature rupture of the membranes
• See “Prenatal ultrasound.”

Third-trimester care is focused on monitoring maternal and fetal well-being and preparing for delivery.

Components

• Monitoring of fetal growth with symphysis-fundal height and ultrasounds as indicated
• Assess for risk factors for adverse pregnancy outcomes; manage as high-risk pregnancy if present.
• Screening for hypertensive pregnancy disorders ^[28]
• Measures to prevent neonatal infection
  • Perform third-trimester STI screening, if indicated.
  • Offer seasonal influenza vaccination and/or COVID booster, if due.
  • 27–36 weeks' gestation: Provide Tdap. ^[84]
  • 32–36 weeks' gestation: Give respiratory syncytial virus vaccine. ^[85]
  • 36–37+6 weeks' gestation: Perform Group B streptococcus prenatal screening.
• Screening for rhesus antibody in Rh-negative nonsensitized individuals ^[31]
  • Perform at 28 weeks' gestation.
  • Administer Anti-D immunoglobulin as needed.
  • See “Management of rhesus-negative individuals without anti-D antibodies” for further information.
• Screening for anemia and gestational diabetes, if not already performed (see “Second-trimester laboratory studies”).
• Preparation for delivery
  • Provide counseling related to peripartum care.
  • Assess for indications for antepartum fetal surveillance and perform, if indicated.
  • From 36 weeks' gestation, use Leopold maneuvers for assessment of fetal presentation. ^[23]
  • Use ultrasound as needed to confirm fetal lie and placental position (see “Prenatal ultrasound”).

In the third trimester, prenatal visits usually increase in frequency to every 2 weeks between 28–36 weeks and weekly thereafter. ^[1]

Third-trimester screening for sexually-transmitted infections (STI) ^[45]

Leopold maneuvers ^[23][86]

• The Leopold maneuvers consist of four abdominal palpation maneuvers used to determine fetal lie, fetal presentation, and fetal position in utero.
  1. Use both hands to palpate the uterine fundus, fetal head, and buttocks to assess:
     • Fetal lie (longitudinal/oblique/transverse)
     • Fundal height
  2. Place each hand on either side of the maternal abdomen to determine the location of the fetal back.
  3. Grasp the lower maternal abdomen above the symphysis to determine the fetal presenting part and if it is engaged.
     • In cephalic presentation, the fetal head is felt as hard, round, and ballottable.
     • In breech presentation, the buttocks are felt as a soft, less movable structure.
  4. Facing the mother's feet, use both hands to determine:
     • The cephalic prominence
     • Fetal attitude (based on the degree of flexion of the fetus's head)
• If abnormal presentation (e.g., breech) is suspected or fetal position cannot be accurately determined, proceed to ultrasound. ^[87][88]

General principles ^[1][7]

Antepartum fetal surveillance testing is typically performed in the third trimester (at ≥ 32 weeks' gestation) to assess fetal well-being and reduce the risk of adverse fetal outcomes. ^[7]

Indications for antepartum fetal surveillance ^[19]

• High-risk pregnancy (e.g., maternal medical conditions or fetal conditions associated with increased risk of fetal hypoxic injury or death)
• Perceived reduction in fetal movement by mother

Modalities ^[7]

• Options include:
  • Kick counts
  • Nonstress test (NST)
  • Contraction stress test (CST)
  • Biophysical profile (BPP)
  • Modified biophysical profile
  • Doppler velocimetry of the umbilical artery (for suspected intrauterine growth restriction)
• A combination of modalities may be utilized. ^[7]

Results and ongoing management

Kick counts ^[7]

• Maternal counting of the number of fetal movements within a particular time period (e.g., 1 or 2 hours).
• Number of kicks reduced compared to prior assessments: Perform additional antepartum surveillance testing.
• Limitations ^[7]
  • No consensus on the optimal duration of monitoring or abnormal number of counts
  • Limited evidence monitoring kick counts affects perinatal adverse outcomes.

Nonstress test (NST) ^[1][7]

NST is a noninvasive test that measures how fetal heart rate (FHR) responds to fetal movements; a rise in fetal heart rate is expected with fetal movement.

Method ^[7]

• Perform electronic fetal heart rate monitoring over a minimum of 20 minutes.
• Review the FHR tracing for FHR accelerations and decelerations. ^[7]
• If no FHR accelerations are observed within the first 20 minutes:
  • Perform vibroacoustic stimulation.
  • Continue with the NST for another 20–40 minutes.

Interpretation ^[1]

• Reactive nonstress test: a normal NST that shows ≥ 2 FHR accelerations over the course of 20 minutes
  • If the indication for testing has resolved, offer reassurance; further testing is not required.
  • If the indication persists, repeat the test (usually at weekly intervals).
• Nonreactive nonstress test: an abnormal NST that shows < 2 FHR accelerations over the course of 20 minutes (after at least 40 minutes of monitoring) ^[7]
  • Causes of a nonreactive NST include:
    • Fetal sleep (most common)
    • Hypoxemia or acidemia
    • Neurologic or cardiac abnormalities
    • Fetal immaturity ^[7]
    • Maternal drug use
  • Next steps: Perform a BPP or CST. ^[1]
• Concerning decelerations : Consider further monitoring or delivery.

Contraction stress test (CST) ^[1][7]

• CST is a test that measures how FHR responds to uterine contractions.
• Can be safely performed, provided there are no contraindications to labor or vaginal delivery. ^[1][89]

Method

• Perform cardiotocography to assess both FHR and uterine contractions.
• If < 3 contractions lasting at least 40 seconds are observed over 10 minutes, induce contractions using either:
  • Nipple stimulation ^[90]
  • IV oxytocin

CST may induce early labor; consider alternative methods of assessing fetal well-being in patients with contraindications to labor or vaginal delivery. ^[1]

Interpretation ^[1][7]

• Negative: absence of late decelerations or significant variable decelerations
• Positive
  • Late decelerations after ≥ 50 % of contractions
  • Consider repeat testing or delivery.
• Equivocal
  • Defined as any of the following:
    • Intermittent variable decelerations or late decelerations
    • Decelerations occurring with uterine tachysystole
  • Repeat in 24 hours.
• Unsatisfactory
  • Tracing uninterpretable or insufficient number of contractions (< 3 in 10 minutes).
  • Repeat with an alternative form of contraction stimulation. ^[91]

Biophysical profile (BPP) ^[7]

The BPP is a noninvasive test consisting of fetal ultrasound of four specified parameters and NST.

Method ^[7]

• An ultrasound examination is performed over 30 minutes to assess the following four parameters:
  • Fetal movement
  • Fetal tone
  • Fetal breathing
  • Amniotic fluid volume
• An NST is then performed if any ultrasound parameter is abnormal but may be omitted if all are normal.
• Each parameter of the ultrasound examination and the NST is given a score of either 0 (abnormal) or 2 (normal)

Interpretation ^[1][7]

• The maximum total score on the biophysical profile is 10 (if NST performed) or 8 (if NST not performed).
• Follow-up recommendations vary based on total score and the presence of oligohydramnios.

Regardless of total biophysical profile score, delivery or close monitoring may be indicated if oligohydramnios is identified. ^[7]

Modified biophysical profile ^[1][7]

• Description: NST plus amniotic fluid measurement by ultrasound ^[92]
• Method: Use one of two methods of assessing amniotic fluid volume.
  • Measurement of the deepest vertical pocket of amniotic fluid
  • Amniotic fluid index
• Interpretation
  • A normal result is a reactive NST plus either: ^[1]
    • Deepest vertical pocket of amniotic fluid > 2 cm
    • Amniotic fluid index of ≥ 5 cm
  • An abnormal result includes any of the following:
    • Nonreactive NST
    • Deepest vertical pocket of amniotic fluid ≤ 2 cm
    • Amniotic fluid index of < 5 cm
• Next steps: For abnormal results, obtain a BPP or CST. ^[7]

Doppler velocimetry of the umbilical artery ^[7]

• Used to monitor fetuses with intrauterine growth restriction (IUGR)
• Assesses diastolic flow velocity of the umbilical artery
• For more information, see:
  • “Overview of maternal and fetal vessel doppler ultrasound”
  • “Intrauterine growth restriction”

General principles ^[93][94]

• Maternal colonization with group B streptococcus; (GBS) is the most significant risk factor for early-onset neonatal GBS infections.
• Routine prenatal screening combined with targeted IV intrapartum prophylactic antibiotics has decreased:
  • Vertical transmission of GBS
  • The number of early-onset neonatal GBS infections

Prenatal screening for GBS ^[93]

Indications

• Routine screening for all women from 36+0 to 37+6 weeks' gestation, regardless of planned delivery method, unless prophylaxis is already indicated, e.g.: ^[93]
  • GBS bacteruria during pregnancy
  • Prior newborn with early-onset GBS infection
• Urgently: women in labor or with ruptured membranes with unknown GBS culture status

Regardless of whether a cesarean or vaginal delivery is planned, screen all pregnant women with indications for GBS screening in order to guide management if unexpected early labor or rupture of membranes occurs. ^[93]

Method of collection

• Swab the lower vagina and introitus, followed by the rectum.
• Use a single flocked swab without a speculum. ^[95]

Laboratory studies

• All patients: GBS culture
• Pregnant individuals with history of severe penicillin reaction: Add reflex clindamycin susceptibility testing. ^[93]
• For urgent indications: Consider adding a rapid nucleic acid amplification test (NAAT). ^[93]

Next steps

• Positive GBS culture: See “Prophylaxis for neonatal GBS infection.”
• Negative GBS culture: Consider repeat testing if the patient is still pregnant in 5 weeks. ^[93]

Prophylaxis for neonatal GBS infection ^[93][95]

• Required for all patients presenting with ruptured membranes or in labor with any indications for GBS prophylaxis.
• Not required if indications are absent or the patient is undergoing a pre-labor cesarean delivery with no rupture of the membranes.

Indications for GBS prophylaxis

• History of early-onset GBS infection in a previous newborn
• Documented GBS colonization during the current pregnancy, i.e.:
  • Positive GBS culture
  • GBS bacteriuria
• Unknown GBS status in current pregnancy PLUS any of the following are present:
  • Any maternal risk factors for neonatal early-onset GBS infection
    • Imminent preterm delivery < 37+0 weeks' gestation or PPROM
    • Prolonged rupture of membranes (i.e., > 18 hours)
    • Maternal temperature ≥ 100.4 °F (38.0 °C)
  • Positive intrapartum NAAT
  • Positive GBS status ; confirmed via culture or bacteriuria in a previous pregnancy ^[93]

Regardless of GBS culture results, intrapartum antibiotic prophylaxis for neonatal GBS is not needed if cesarean delivery is performed prior to the onset of labor and with intact membranes. ^[93]

Antibiotic regimens

Antibiotics should ideally be initiated at least 4 hours prior to delivery.

• No penicillin reaction: IV β-lactam antibiotics, i.e., IV penicillin G; (off-label) OR IV ampicillin (off-label) ^[93]
• Penicillin allergy: Tailor based on susceptibility testing and allergy severity.
  • Nonsevere penicillin reaction: IV cefazolin (off-label) ^[93]
  • Severe penicillin reaction
    • First line: IV clindamycin (off-label)
    • Alternative if GBS is clindamycin-resistant: IV vancomycin (off-label) ^[93]

If an intraamniotic infection is suspected, initiate treatment with broad-spectrum antibiotics rather than prophylactic antibiotics. ^[93]

While administration of antibiotics for at least 4 hours prior to delivery is preferred, it should not delay any necessary obstetric interventions. ^[93]

GBS prophylaxis considerations in preterm labor

• Manage patients in consultation with an obstetrician. ^[93]
• Start intrapartum prophylactic antibiotics for GBS.
• If GBS status is unknown, collect the GBS culture and NAAT prior to starting antibiotics.
• If preterm labor is arrested, GBS prophylaxis may be discontinued.
• If previously arrested preterm labor resumes:
  • Review prior GBS culture results to determine if there are indications for GBS prophylaxis.
  • For negative GBS culture results, repeat GBS NAAT and culture if ≥ 5 weeks since the prior result.

• Beginning in early pregnancy and continuing throughout pregnancy, educate patients on factors related to maternal and fetal health, including: ^[1]
  • Nutrition and weight gain during pregnancy
  • Physical activity during pregnancy
  • Dental care, travel, use of medications, and work during pregnancy (see “Other health and safety counseling during pregnancy”).
• In the second and third trimesters, provide counseling related to peripartum care. ^[1]

General principles ^[27][96]

• Dietary intake during pregnancy should be optimized to meet the demands of both the mother and the fetus. ^[96]
• Appropriate weight gain and nutrition should be assessed on an individual basis.
• Encourage pregnant women to follow a well-balanced diet and avoid restrictive diet plans.
• A daily multivitamin that includes folic acid is generally recommended for the duration of pregnancy. ^[96][97]
• For patients with special dietary needs (e.g., those with diabetes, vegetarians), consider referral to a nutritionist. ^[1]

Recommended dietary intake and supplementation ^[97][98]

• Calories: Average daily calorie requirements increase in the second and third trimesters.
  • Women with a normal pre-pregnancy BMI
    • Second trimester: additional 340 calories/day
    • Third trimester: additional 452 calories/day
  • For women with a pre-pregnancy BMI ≥ 25, tailor calorie recommendations to recommended weight gain during pregnancy.
• Protein: 71 grams/day is recommended. ^[98]
• Carbohydrates: 175 grams/day is recommended, including 25–36 grams of fiber per day. ^[98]
• Fats
  • It is recommended that 20–35% of daily calorie intake come from fats. ^[98]
  • Adequate intake of Omega‐3 fatty acids is recommended. ^{[98][99][100]}

Micronutrients during pregnancy

Patients considering pregnancy should aim for similar intakes (see “Preconception counseling”).

Excessive consumption of vitamin A during pregnancy may be teratogenic. ^[1]

Vegetarian mothers are at risk of deficiencies in vitamin D, iron, calcium, vitamin B12, and zinc; consider laboratory evaluation as indicated. ^[1][97]

Dietary restrictions during pregnancy ^[105]

• Limit caffeine: to < 200 mg daily (∼ 2 cups of coffee or ∼ 4 cups of caffeinated tea) ^[112]
• Avoid alcohol use throughout pregnancy. ^[113]
• Avoid foods associated with higher risk of foodborne illness, e.g.: ^[23]
  • Raw or undercooked seafood: risk of contamination with parasites and norovirus
  • Raw or undercooked meat: risk of Listeria and Toxoplasma contamination
  • Deli meats and hot dogs: risk of Listeria contamination
  • Raw eggs: risk of Salmonella contamination
  • Unwashed fruits and vegetables: risk of Listeria and Toxoplasma contamination
  • Unpasteurized dairy products: risk of Listeria and Toxoplasma contamination
• Avoid seafood with possibly high levels of methylmercury: such as tilefish, swordfish, shark, mackerel, and bigeye tuna. ^[1]

Consumption of raw or undercooked meats, unpasteurized dairy products, and unwashed fruits and vegetables by pregnant women can increase the risk of congenital toxoplasmosis and congenital listeriosis and should be avoided. ^[23]

Recommended weight gain during pregnancy ^[1][105]

• Total recommended weight gain is determined by BMI prior to pregnancy. ^[27]
  • Singleton pregnancies
    • BMI < 18.5 (underweight): 28–40 lb (12.7–18.1 kg)
    • BMI 18.5–24.9 (normal weight): 25–35 lb (11.3–15.9 kg)
    • BMI 25–29.9 (overweight): 15–25 lb (6.8–11.3 kg)
    • BMI ≥ 30 (obese): 11–20 lb (5–9.1 kg)
  • Twin pregnancies
    • BMI 18.5–24.9 (normal weight): 37–54 lb (17–25 kg)
    • BMI 25–29.9 (overweight): 31–50 lb (14–23 kg)
    • BMI ≥ 30 (obese): 25–42 lb (11–19 kg)
• Both excessive and inadequate gestational weight gain can impact fetal and maternal outcomes. ^[114]

During the second and third trimesters, recommended weekly weight gain is 0.5 lb/week if pre-pregnancy BMI ≥ 30, 0.6 lb/week if pre-pregnancy BMI 25–29.9, and 1 lb/week if pre-pregnancy BMI < 25. ^[27]

General principles ^[124]

• Evaluate all patients for contraindications to aerobic exercise in pregnancy prior to recommending physical activity.
• Regular physical activity is recommended during most pregnancies.
  • Educate patients on safe and unsafe activities and advise activity avoidance or modification as needed. ^[124][125]
  • Patients should aim for ≥ 20–30 minutes of aerobic and/or strength-training exercise most days of the week. ^[1]
  • In the absence of medical or surgical complications, physical activity may resume soon after delivery. ^[124]
• Consider occupational accommodations for women with jobs requiring high levels of physical effort or potentially unsafe activities. ^[126]

Contraindications to aerobic exercise in pregnancy ^[1]

• Restrictive lung disease
• Hemodynamically significant heart disease
• Severe anemia ^[125]
• Cervical insufficiency
• Premature rupture of membranes or premature labor
• Gestational hypertension or preeclampsia
• Placenta previa or vaginal bleeding

Safe and unsafe sports during pregnancy ^[124][125]

Physical activity should be stopped and the patient should notify their provider in the event of any the following: antepartum or postpartum hemorrhage, uterine contractions, amniotic fluid leakage, chest pain, dyspnea before exertion, dizziness, headaches, calf pain/swelling, and/or muscle weakness with impaired balance. ^[124]

Dental care during pregnancy ^[1]

• Poor oral health may be associated with preterm delivery.
• Encourage regular brushing, flossing, and cleanings.
• Educate patients about common dental problems seen in pregnancy.

Travel during pregnancy

• Encourage pregnant individuals to always wear a seatbelt. ^[127]
• Provide counseling before travel. Discuss: ^[128][129]
  • Avoiding travel if risk factors for adverse pregnancy outcomes are present
  • Infection prevention and control
    • Consider if additional vaccinations are required.
    • Advise against travel to areas with active Zika virus outbreaks or malaria.
    • Recommend strict food hygiene and water hygiene precautions.
  • Planned activities (see “Safe and unsafe sports during pregnancy”)
  • Risk of VTE with long-haul travel ^[129][130]
  • Airline and cruise ship restrictions on travel in late pregnancy
  • Importance of travel insurance and carrying a copy of medical records

Pregnant women should be informed that the most common obstetric emergencies occur in the first and third trimesters and they may, therefore, prefer to restrict travel to the second trimester. ^[128]

Medications and substance use ^[1]

• Advise the patient to avoid tobacco, alcohol, and recreational drugs.
• Ensure all prescribing clinicians are aware the patient is pregnant.
• Have the patient check with a healthcare professional before taking over-the-counter medications, supplements, or herbal preparations.

Work during pregnancy ^[126]

• Educate patients on occupational hazards, e.g.:
  • Known hazards: toxic exposures (e.g., heavy metals, pesticides, ionizing radiation)
  • Suspected hazards
    • Standing/walking for long periods of time (> 3 hours a day)
    • Heavy lifting
    • Working > 40 hours a week
• Support patients in seeking workplace accommodations where appropriate.

When writing a work accommodation note for pregnant patients, make sure to be specific and outline reasonable limitations to avoid the note being used as grounds for dismissal. ^[126]

• Inform patients about clinical features of preterm labor and rupture of membranes, and when to seek medical care.
• Review any maternal birth expectations and provide counseling on options, including: ^[1][131]
  • Methods of delivery (spontaneous vaginal delivery, assisted vaginal delivery, cesarean delivery)
  • Labor pain management (e.g., epidural anesthesia)
  • Umbilical cord blood banking
  • Breastfeeding and formula feeding
• If complex delivery is anticipated, discuss options with the patient, e.g.: ^[1]
  • Breech presentation: cesarean delivery, vaginal breech delivery, or external cephalic version
  • Previous cesarean section: trial of labor, scheduled cesarean delivery
• Encourage patients and other individuals who will be involved in the childbirth to attend educational classes.
• Advise patients to find an infant healthcare provider prior to delivery.
• Discuss neonatal procedures that may be performed prior to hospital discharge, e.g.:
  • Hepatitis B immunization
  • Routine neonatal ophthalmic antibiotic prophylaxis
  • Parenteral vitamin K administration for prevention of VKDB
  • Circumcision
• Provide basic counseling on child safety.
• Offer guidance on contraception in postpartum individuals. ^[1]

• One-Minute Telegram 84-2023-1/3: Continue monitoring BP during pregnancy

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