Fetal well-being depends on maternal health (see Chapter 6 for gestational diabetes screening). Many routine prenatal tests assess maternal health and well-being. Prenatal testing usually includes a complete blood count or hemoglobin and hematocrit, Rh type and ABO blood group, red cell antibody screening, rubella immunity status, glucose challenge testing (see Chapter 6), urinalysis, maternal serum alpha1-fetoprotein (MSAFP) or maternal quadruple marker test or quad screen, hepatitis B testing, culture for sexually transmitted diseases, the syphilis immunoglobulin G (IgG) test, and surveillance for group B streptococci. Screening for HIV infection is recommended for all pregnant women to improve the care of HIV-positive women and to identify infants at risk; perinatal transmission is the primary route of HIV infection in children.
Tests in this chapter monitor the status of the maternal–fetal unit, identify the fetus at risk for intrauterine asphyxia, aid in the early diagnosis of infection, and identify genetic and biochemical disorders and major anomalies. (See Chapter 11 for more on genetic disorders.) Tests are also performed to predict normal fetal outcome or to identify the fetus at risk for asphyxia during labor (Table 15.1).
Noninvasive prenatal testing for fetal aneuploidy is available for women at increased risk of aneuploidy. Extraction of fetal cells from the maternal circulation (fetal cell sorting) is performed for screening of trisomy 21, 18, and 13, although it does not replace the need for diagnosis by chorionic villus sampling (CVS) or amniocentesis.