• Clinical science

Prenatal care

Abstract

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 learning card 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).

General principles

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:

  • Weight monitoring: to avoid fetal developmental problems (if weight gain is less than the recommended amount), fetal macrosomia, or maternal obesity (if weight gain is above normal)
  • Blood pressure monitoring: early detection of pregnancy-induced hypertension
  • First-trimester screening: : battery of tests for the screening of chromosomopathies
  • Physical examination
    • Fundal height and position of the fetus (identified through the first Leopold's maneuver)
    • Fetal heart monitoring (via ultrasound or cardiogram)
  • Laboratory

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

Prenatal diagnostics

  • All pregnant women (regardless of age) should be offered noninvasive aneuploidy screening tests (before 20 weeks gestation)
  • Possible tests:
    • Testing maternal serum; : measurement of specific biomarkers and ultrasound markers that indicate an increased risk for aneuploidy
    • Cell-free fetal DNA testing
  • 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

  • Risk of aneuploidy is evaluated based on maternal age, lab results, and ultrasound.
  • If abnormal, provide counseling and perform CVS or amniocentesis
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
  • From the 15th week of pregnancy onwards
  • Or in exceptional cases from the 12th week of pregnancy.
  • Amniotic fluid analysis: AF is extracted under sonographic guidance via transabdominal puncture for diagnostic purposes
  • Miscarriage (approximate risk: 0.5–1%)
  • Premature rupture of the membranes
  • Infection

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

Leopold's maneuvers

  • 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]

Antepartum fetal surveillance

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

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 30-minute period

References:[16][17][18][19][20]

Ultrasound during pregnancy

Doppler ultrasound

Vessel

Pathological findings
Uterine artery Early diastolic notch

Umbilical artery

Decline or loss of end diastolic flow velocity or negative flow

Fetal medial cerebral artery

Increased diastolic flow velocity

References:[21][22][23][24]