Midtrimester amniocentesis in twin pregnancies.

Twenty-two twin pregnancies were subjected to second-trimester genetic amniocentesis. Arguments for and against tapping both sacs were discussed. Nineteen of the 22 patients studied underwent amniocentesis because of advanced maternal age (35 years or greater). The remaining indications included previous omphalocele, previous Down's syndrome, and previous neural tube defect. Except for one instance, amniotic fluid was obtained from both sacs. There were no other adverse sequelae other than transient leakage of fluid in one case. Two sets of twins were stillborn; in neither case was there a temporal relationship between the procedure and the fetal loss. Furthermore, there was no clinical or postmortem evidence that in any way could implicate the procedure as the cause of the fetal death. Based on literature review and the cases cited in the present investigation, it is the opinion of the authors that these procedures are safe when performed by experienced personnel under ultrasonic guidance.