Complications of amniocentesis: a review.

Amniocentesis is usually employed at two distinct times in gestation, either early in the second trimester or during the third trimester. Although major complications are infrequent, the types of complications encountered and their relative risk of occurrence differ depending on the time of gestation. Bloody contamination of amniotic fluid is both more frequent and troublesome in genetic amniocentesis performed in the second trimester. Serious injury to the placental vessels or to the mother appears to be a greater risk in the third trimester. The used of ultrasound to identify the placental and fetal location can help to better assess the hazards of amniocentesis for the individual patient and may reduce the risk if amniocentesis is performed immediately following the ultrasound examination.