Amniocentesis, which involves extracting amniotic fluid in order to analyze fetal cells for genetic abnormalities, is usually done between week 14 and 20 of pregnancy. Increasingly, however, in response to women who would like an earlier diagnosis, doctors are performing the procedure at 11 or 12 weeks. But getting an early answer is not without risks.
A 1999 study revealed that when amniocentesis is performed at 11 or 12 weeks the possibility of foot deformities in babies increases as well. Canadian researchers compared the incidence of clubfoot among babies whose mothers had amniocentesis at 11 to 12 weeks and those who had the test at 15 to 16 weeks. Those who had the test earlier had a 1.3 percent chance that the baby would be delivered with clubfoot, compared with .1 percent when amnio was performed at the standard time. The researchers speculate that the loss of amniotic fluid during the test and subsequent leakage may decrease the size of the amniotic sac, thereby squeezing the fetus's feet while they're still developing.