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Prenatal care

Last updated: February 10, 2021

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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 gestational week, 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.

Initial examination (∼ 10 weeks' gestation)

Subsequent examinations

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

References:[1][2][3][4]

  • All pregnant women (regardless of age) should be offered noninvasive aneuploidy screening tests (before 20 weeks gestation)
  • Possible tests:
  • All pregnant women (regardless of age) should be given the alternative option to undergo invasive genetic testing; (amniocentesis or CVS)
  • Pre-test counseling must be provided: inform the parents that screening is voluntary; explain the difference between screening and diagnostic tests, risk of false positive and false negative tests, explain option of terminating the pregnancy if aneuploidy is diagnosed

Noninvasive screening tests

Test Timing Description Evaluation Conditions
First-trimester combined screening

11–13 weeks gestation

Quad screen test 15–20 weeks gestation
  • Risk is evaluated based on maternal age, lab results, and ultrasound.
  • If risk is elevated, counseling and invasive genetic testing (CVS or amniocentesis) should be offered for chromosome analysis
Triple screen test 15–20 weeks gestation
Sequential integrated test 10–13 weeks gestation followed by 15–20 weeks gestation
Cell-free fetal DNA testing (cffDNA)

From 10 weeks gestation onwards

  • Fetal DNA is isolated from a maternal blood specimen for genetic testing

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

Invasive diagnostic tests

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

References:[3][5][6][7][8][9][10][11][12]

  • 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
20th Between the symphysis and navel
24th Navel
32nd Between the navel and xiphoid
36th Peak: at the costal arch
40th Two finger widths below the costal arch

References:[13][14][15]

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

  • Nonstress test (NST): a noninvasive test (CTG) that measures FHR reactivity to fetal movements
  • Contraction stress test (CST): measures FHR reactivity in response to uterine contractions
  • Biophysical profile (BPP): 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).
    • Interpretation
      • Total score ≥ 8 points: no signs of fetal compromise at the time of testing → reassurance
      • Total score ≤ 4 points: potential fetal compromise → delivery is indicated (if pregnancy duration is < 32 0/7 weeks, administer steroids and continue close monitoring)
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 [16]

References:[17][18][19][20][21]

Doppler ultrasound

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:[22][23][24][25]

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