Prenatal care

Last updated: September 19, 2022

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Prenatal care refers to the healthcare that women receive throughout pregnancy. Guidelines for routine prenatal care determine the scope and frequency of prenatal visits and screening. Prenatal visits aim to detect high-risk pregnancies and to monitor the course of pregnancy and fetal development. They involve recording the mother's medical history, consultations, physical and gynecological examinations, laboratory diagnostic analyses, and regular ultrasound screening. Prenatal care visits initially occur once monthly until the 28th week of gestation, twice monthly between the 28th and 36th week, and weekly after the 36th week. This article covers the general principles of prenatal care, as well as some of the most important diagnostic methods routinely used for the care of pregnant women (i.e., Leopold's maneuvers, obstetric ultrasound).

Frequency of check-ups

  • Until the 28th week of pregnancy: monthly
  • From the 28th week until the 36th week: every two weeks
  • From the 36th week until birth: every week
  • In high-risk pregnancies, frequent visits are usually warranted.

Preventive ethics

Informed consent should be obtained during the prenatal period to prevent and manage ethical conflicts between pregnant individuals and their healthcare providers.

  • Facilitates advance discussion of procedures that may be necessary during the perinatal period (e.g., cesarean delivery, management of fetal anomalies).

    • Ensures a safe environment for addressing concerns and reservations
    • Encourages informed decision-making
    • Avoids miscommunication and disagreement
  • Because any pregnancy can become high-risk, pregnant individuals should be informed about the potential need for cesarean delivery and encouraged to discuss any concerns ahead of time.

Initial examination (∼ 10 weeks of gestation) [1]

Indications for third-trimester screening for sexually-transmitted infections (STI)

  • Chlamydia
    • < 25 years of age
    • Individuals with new and/or multiple sexual partners, a sexual partner with other partners, and/or a sexual partner who has a STI
  • Gonorrhea
    • Living in an area with high prevalence
    • Previous or current STI
    • Individuals with new and/or multiple sex partners
    • Inconsistent use of barrier methods in nonmonogamous relationships
    • Individuals who engage in transactional sex
  • Syphilis (28 weeks and at delivery)
    • Previous infection with any STI during pregnancy
    • Individuals with multiple sexual partners, a new partner, and/or partner who has a STI
    • Recreational drug use
    • Living in an area with high prevalence
    • No previous test
    • Positive test in first trimester
  • HIV: risk factors for HIV infection
  • Hepatitis B
    • No prenatal screening
    • Signs or symptoms of hepatitis upon admission for delivery
    • Individuals with 2 or more sexual partners in the last six months
    • Previous or current STI
    • Individuals who inject drugs
    • Individuals with a sexual partner who is HBsAg-positive

Subsequent examinations

The following should be performed during each prenatal care visit regardless of pregnancy-related complaints and symptoms:

Prophylaxis for neonatal GBS infection

Noninvasive screening tests [3][4]

Overview of noninvasive screening tests
Test Timing Description Evaluation Conditions
First-trimester combined screening
  • See table below.
Quad screen test
  • In maternal serum
Triple screen test
Sequential integrated test
Cell-free fetal DNA testing (cffDNA)

First trimester combined screening test

Overview of first trimester combined screening test
Condition HCG PAPP-A Nuchal translucency
Trisomy 21

Thickened nuchal fold (> 95th percentile)

Trisomy 18 ↓↓
Trisomy 13 ↓↓
Molar pregnancy ↑↑ - -
Ectopic pregnancy - -

Quad and triple screening tests

Overview of quad and triple screening tests
Condition HCG AFP Estriol Inhibin A
Trisomy 21
Trisomy 18 ↓↓ ↓↓ ↔︎ or ↓
Neural tube defects ↔︎ ↔︎
Abdominal wall defects

AFP is interpreted based on the fetal gestational age. The most common cause for an abnormal AFP in maternal serum is an inaccurate fetal gestational age.

Invasive diagnostic tests

Overview of invasive diagnostic tests
Test Timing Procedure Indications Complications
Chorionic villus sampling (CVS)
  • 10–13 weeks
  • Transcervical or transabdominal removal of chorionic tissue under sonographic guidance
  • Analysis of DNA for genetic diagnosis in early pregnancy
Amniocentesis
  • Miscarriage (approximate risk: 0.5–1%)
  • Premature rupture of the membranes
  • Infection
Cordocentesis

Four abdominal palpation maneuvers used during physical examination to determine the presentation, position, and engagement of the fetus in utero.

  • First: bimanual examination of the fetal position; (longitudinal/oblique/transverse) and fundal height
  • Second: bimanual examination of the location of the fetal back (i.e., either on the mother's left or right side)
  • Third
    • One hand grasps above the symphysis in an attempt to determine if the presenting part of the fetus is engaged.
    • In cases of cephalic presentation , the fetal head feels hard and ballotable; if the fetus is in a breech position, a soft and less movable rump can be felt.
  • Fourth: : Bimanual determination of the location of the fetal brow and the degree of flexion of the fetus's head. Usually performed during the later stages of pregnancy when the fetus has entered the pelvic inlet.
Week of pregnancy Fundal height during pregnancy
12th Just above the symphysis
16th Between the symphysis and navel
20th Navel
32nd Between the navel and xiphoid
36th Peak: at the costal arch
40th Two finger widths below the costal arch

References:[6][7][8]

The following tests are performed in high-risk pregnancies to assess the risk of antenatal fetal death.

Nonstress test (NST)

Interpretation

Contraction stress test (CST)

  • Measures FHR reactivity in response to uterine contractions
  • Contractions are stimulated with oxytocin administration.

Biophysical profile (BPP)

  • Definition: a noninvasive test that evaluates the risk of antenatal fetal death, usually performed after the 28th gestational week
  • Measured parameters: each parameter receives a score of either 0 (abnormal) or 2 (normal) points (see table below).
Biophysical profile scoring criteria
Parameter Normal results (= 2 points)
Fetal movement
  • ≥ 3 body or limb movements within a 30-minute period
Fetal tone
  • ≥ 1 episodes of a fetal extremity or fetal spine extension with return to flexion
Fetal breathing
  • ≥ 1 rhythmic breathing episode(s) ≥ 30 seconds within a 30-minute period
Amniotic fluid volume
  • A single deepest vertical pocket ≥ 2 cm with a horizontal dimension ≥ 1 cm.
Nonstress test
  • ≥ 2 episodes of FHR accelerations of ≥15 bpm and ≥15 seconds associated with fetal movement within a 20-minute period [9]

Interpretation

  • Total score ≥ 8 points: no signs of fetal compromise at the time of testing → reassurance
  • Total score 5–7 points: unclear risk of fetal compromise → repeat BPP within 24 hours
  • Total score ≤ 4 points: potential fetal compromise → delivery is indicated (if pregnancy duration is < 32 0/7 weeks, administer steroids and continue close monitoring)

References:[10][11]

Standard examinations

First-trimester ultrasound [12]

Typically performed transvaginally around 6–8 weeks' gestation.

Second- or third-trimester ultrasound

Typically performed transabdominally around 18–22 weeks' gestation.

Additional examinations

In case of high-risk pregnancies or complications during pregnancy (e.g., premature rupture of membranes or bleeding during pregnancy), additional ultrasound exams should be performed.

Vessel

Pathological findings
Uterine artery Early diastolic notch

Umbilical artery

Decline or loss of end-diastolic flow velocity or negative flow

Fetal middle cerebral artery

Increased diastolic flow velocity

References:[13]

  1. STDs during Pregnancy - CDC Fact Sheet (Detailed). https://www.cdc.gov/std/pregnancy/stdfact-pregnancy-detailed.htm. Updated: April 12, 2022. Accessed: September 23, 2022.
  2. Puopolo KM, Lynfield R, Cummings JJ. Management of Infants at Risk for Group B Streptococcal Disease. Pediatrics. 2019; 144 (2): p.e20191881. doi: 10.1542/peds.2019-1881 . | Open in Read by QxMD
  3. Hull AD, Moore TR. Antepartum Fetal Assessment. Elsevier ; 2005 : p. 127-138
  4. Beckmann CRB. Obstetrics and Gynecology. Lippincott Williams & Wilkins ; 2010
  5. ACOG Guidelines at a Glance: Antepartum Fetal Surveillance. http://contemporaryobgyn.modernmedicine.com/contemporary-obgyn/news/acog-guidelines-glance-antepartum-fetal-surveillance?page=0,2. Updated: February 6, 2015. Accessed: November 7, 2017.
  6. Gibbs RS. Danforth's Obstetrics and Gynecology. Lippincott Williams & Wilkins ; 2008
  7. Haydon J. Genetics in Practice. John Wiley & Sons ; 2007
  8. NIPT Summary of Recommendations. https://www.acog.org/advocacy/policy-priorities/non-invasive-prenatal-testing/current-acog-guidance. Updated: January 1, 2022. Accessed: July 7, 2022.
  9. Dudenhausen JW, Obladen M. Practical Obstetrics. Walter de Gruyter GmbH & Co KG ; 2014
  10. Scott Ricci S, Kyle T. Maternity and Pediatric Nursing. Lippincott Williams & Wilkins ; 2009
  11. Saxena R. Bedside Obstetrics & Gynecology. JP Medical Ltd ; 2014
  12. Obstetric Ultrasound Examination (Position Paper). https://www.aafp.org/about/policies/all/obstetric-ultrasound.html. Updated: April 6, 2018. Accessed: January 5, 2022.
  13. Dutta DC, Konar H. Textbook of Obstetrics. Jaypee Brothers Medical Publishers ; 2015

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