The significance of meconium in midtrimester genetic amniocentesis.

Since the advent in recent years of midtrimester amniocentesis for genetic testing, there has been an increasing number of reports of occasional instances of meconium-stained amniotic fluid of uncertain prognostic significance. Previous reports have suggested a fetal mortality of 30%. With larger series now available for study, more accurate information on the incidence of this occurrence and its significance is presented. The present series consists of 4709 consecutive amniocenteses performed from 1978 to 1983, at two genetic testing centers in Portland, Oregon. Meconium-stained amniotic fluid was found in 79 cases, for an incidence of 1.67%. Contrary to previously published reports, the fetal mortality was 5.06%. Thus the finding of meconium-stained amniotic fluid during midtrimester genetic amniocentesis may not carry the ominous prognosis that originally might have been predicted.