Fetal anomalies may not become apparent until after 20 weeks. This can be helpful in the decision to induce or follow postdated pregnancies, high-risk pregnancies, or diabetic pregnancies. Pregnancies in women 35 years of age or older. Previous pregnancy resulting in the birth of a child with a chromosomal abnormality. Down syndrome or other chromosome abnormality in either parent or close family member.
Mother is a carrier of any X-linked disease.
Neural tube defect in either parent or a first-degree relative. Previous child born with a neural tube defect. Either parent is a carrier of a genetically transmitted metabolic disease. Pregnancy after three or more spontaneous abortions. Done during late pregnancy to determine fetal lung maturity based on phospholipids.