Sonography at the time of genetic amniocentesis to screen for fetal malformations.

Obstetric ultrasound performed in conjunction with genetic amniocentesis at 14-18 weeks' gestation identified 16 fetuses with structural malformations among 4781 examinations. The outcomes for these 16 fetuses included 12 terminations, two fetal deaths, one related death six months after birth, and one transient abnormality with no apparent significant sequelae. The ultrasound examination failed to detect at least nine other fetuses with structural malformations. The relatively small size and early stage of development of the fetuses at the time of genetic amniocentesis appears to have contributed to the failure of ultrasound to detect these malformations. A brief search for fetal malformations during obstetric ultrasound performed at early genetic amniocentesis appears productive enough to be worthwhile. However, if there is a special indication to search for fetal malformations, the ultrasound examination should probably be repeated later.