In addition to the routine laboratory tests performed at the initial antepartum visit, additional tests are performed at specific intervals throughout the pregnancy to screen for birth defects and other conditions. The specific tests and intervals for each are indicated on the Antepartum Record (see Appendix C). Additional laboratory testing, such as testing for sexually transmitted diseases or tuberculosis, are recommended or offered on the basis of the patient’s his-tory, physical examination, parental desire, or in response to public health guidelines.
There are several options for screening for fetal aneuploidy (abnormal number of chromosomes) such as trisomy 18 and 21. Options for screening include:
· First trimester screening (10–13 weeks of gestation),which includes serum screening for pregnancy-associated plasma protein A (PPA) and beta-hCG, and an ultrasound assessment of nuchal transparency.
· Second trimester screening (15–20 weeks of gestation)consisting of triple (maternal serum α-fetal protein [MSAFP], estriol, and hCG) or quadruple (“quad”) (MSAFP, hCG, estriol, and inhibin) screening tests.
· Integrated first-and-second trimester screening, which includes all of the first trimester screening tests listed in addition to a PAPP-A test and a quad screen, with or without an ultrasound examination for neural tube defects, in the second trimester.
glucose challenge test (GCT) is a screening test per-formed for gestational diabetes in the third trimester, unless the pregnant patient is obese or at high risk for developing diabetes. In these cases, the test should be performed at the first visit. If the test result is abnormal, a glucose tolerancetest (GTT) is performed to confirm diabetes. Universalscreening for group B streptococcus (GBS) is performed at 32 to 36 weeks’ gestation, and treatment is based on cul-ture results. In addition, measurement of hemoglobin and hematocrit levels is repeated in the third trimester.