First-trimester invasive procedures and congenital abnormalities.

A prospective study was undertaken to determine whether first-trimester amniocentesis or chorion villus sampling was associated with an increased incidence of congenital anomalies. The infants of mothers who had undergone first-trimester amniocentesis (EA) (n = 352), chorion villus sampling (CVS) (n = 348) or no invasive antenatal procedure (controls) (n = 264) were examined at a median age of 5 months. Both the EA and CVS groups had a higher proportion of infants with congenital anomalies (n = 18 and n = 22, respectively) than the control group (n = 4) (p < 0.01). Certain of the abnormalities, however, affected only single infants. Compression abnormalities were more common in the EA group than in the controls (p < 0.05), but not in the CVS group. The isolated limb abnormalities which occurred were minor anomalies affecting the digits and were seen in both the CVS (n = 6) and EA (n = 3) groups. First-trimester invasive procedures are thus associated with an excess of congenital anomalies.