Maternal-fetal medicine sub-specialists are obstetrician-gynecologists who undergo an additional 3 years of specialized training in the assessment and management of high-risk pregnancies.

 As a result, they are able to take care of pregnant women who have special medical problems (e.g. heart or kidney disease, hypertension, diabetes, and thrombophilia), pregnant women who are at risk for pregnancy-related complications (e.g. preterm labour, pre-eclampsia, and twin or triplet pregnancies), and pregnant women with fetuses at risk.

Fetuses may be at risk because of chromosomal or congenital abnormalities, maternal disease, infections, genetic diseases, and growth restriction.

Maternal-fetal medicine specialists have training in obstetric ultrasound, invasive prenatal diagnosis and the management of high-risk pregnancies. The field of maternal-fetal medicine is one of the most rapidly evolving fields in medicine especially with regard to the fetus. Research is being carried out within the fields of fetal gene and stem cell therapy in hope to provide early treatment for genetic disorders, open fetal surgery for the correction of birth defects like congenital heart disease, and the prevention of preeclampsia.

Maternal-fetal medicine specialists are the leaders in high-risk obstetric care and serve as consultants to general obstetricians, general practitioners, and midwives. In addition to caring for women with high-risk pregnancies, maternal-fetal medicine specialists are leaders in medical education in obstetrics and in research that identifies better ways to evaluate and care for pregnant women and their fetuses.