Subsequent tests along the way
- Although no study has ever found that routine ultrasound in normal pregnancy improves outcome, the standard of care in most communities at this time is to request that at least one ultrasound be performed. If early dating is required (for example, when needed for genetic screening), or if the mother has experienced a problem, the scan may be performed in the first trimester. If only one is planned, it's best to request the scan for 18 to 20 weeks, when organ development is well established and dates can still be ascertained with accuracy.
- Many clinics have discontinued the time-honored (but not evidence-based) practice of testing urine at each visit for protein, glucose and ketones. The research tells us that women without such testing do just as well. A urine specimen, however, should always be collected if the mother has a history of repeated urinary tract infection, kidney disease or infection, diabetes (including gestational diabetes) or preeclampsia. If a mother identifies herself as or is suspected of being a street-drug user, a urine tox screen should be requested.
- Between 15 and 22 weeks, a quad screen (triple screen or AFP) is offered to identify pregnancies at a higher risk for Down syndrome, trisomy 18 or an open neural tube defect.
- At 26 to 28 weeks, another hemoglobin level is performed, a urine culture is collected to identify bacteria that can increase the risk for preterm labor, an Rh antibody test is done if the mother is Rh-negative and, lastly, the glucose challenge test (GCT) is performed to identify women with gestational diabetes. Occasionally, a hepatitis C test is requested if the mother is contemplating a water birth.
- A vaginal culture for group B beta strep, an infection affecting about 30 percent of the population, should be collected at 36 to 37 weeks. If the test result is positive, antibiotics will be given to the mother in labor to prevent neonatal infection.