What are the common nonemergent indications to perform a detailed extended obstetric ultrasound study?
Nonemergent indicators of abnormal pregnancy that may prompt use of a detailed extended examination include:
- • Abnormal maternal screening. This includes the sequential screen which includes measurement of some combination of maternal serum alpha fetoprotein (AFP), pregnancy-associated plasma protein A (PAPP-A), estriol, human chorionic gonadotropin (hCG), and dimeric inhibin A (DIA). More recent screening involves the cell-free DNA screening test, also referred to as noninvasive prenatal testing (NIPT), which examines the fetal DNA found in maternal blood and can detect trisomy 13, 18, and 21 and Turner syndrome. A patient who has an abnormal result of chorionic villus sampling or amniocentesis would also be a candidate for a detailed extended ultrasound study.
- • Size-date discrepancy (includes polyhydramnios and oligohydramnios as causes).
- • Changes in fetal movement. This can be an emergency if fetal activity changes from normal to markedly decreased or absent, as it indicates fetal distress at a minimum and fetal demise in the worst case scenario.
- • History of previous pregnancy (or pregnancies) resulting in abnormal fetuses or with spontaneous abortions that have shown chromosomal abnormalities.
- • Advanced maternal age (i.e., the patient is, or will turn, ≥ 35 years of age during the pregnancy).
- • Family history of congenital anomalies.
- • Maternal infections exposure (TORCH-toxoplasmosis, other, rubella, cytomegalovirus, herpes; other includes such known teratogenic virus as parvovirus B19).