First-Trimester Determination of Complications of Late Pregnancy

The term harelip, used to describe facial clefts, arose from a belief that the defect originated from the mother being startled by a hare during her pregnancy.¹ The concept that congenital structural abnormalities of the fetus developed from events during pregnancy is called maternal impression and it continued to be seriously discussed well into the 19th century.¹ However, it is now known that the vast majority of congenital structural fetal malformations are a consequence of aneuploidy or abnormal embryonic development in the first 8 weeks postconception. A series of studies suggest that other complications of pregnancy, such as intrauterine growth restriction, preterm birth, and stillbirth, also have their origins, at least in part, in very early pregnancy. These observations raise the possibility that women who are at increased risk of adverse outcome in late pregnancy may be identifiable in the first trimester of pregnancy, with the potential for trials of screening and early intervention.