Preterm delivery: a risk factor for retained placenta

Retained placenta is a placenta that does not spontaneously separate from the uterus within 30 minutes after delivery of the infant. Retained placenta appears to occur at a higher rate in preterm deliveries (between 20 and 36 gestational weeks) than in term deliveries. Since approximately one-fifth of the women who deliver preterm infants also have microbiological evidence of bacteria in the amniotic fluid (in which the fetus floats), it is possible that retention of the placenta is associated with infection. To learn more about this, medical records were reviewed from 231 preterm vaginal deliveries and 561 term vaginal deliveries (the latter served as controls) at one medical facility. The preterm patients had undergone amniocentesis (removal of a sample of amniotic fluid) upon admission to the hospital for evaluation of possible microorganism content. One hundred twenty-five women had preterm labor with intact membranes (the membranes that surround the fetus) and 106 had premature rupture of membranes (PROM). Slightly more than 9 percent of the women with preterm vaginal delivery had retained placentas, compared with slightly more than 1 percent of the women with term deliveries, a statistically significant difference. No difference in the proportion of retained placentas was found between the PROM and non-PROM groups. The greater incidence of retained placenta in preterm births was not associated with either a positive result for microorganisms or with the presence of chorioamnionitis (inflammation of the amniotic membranes). The results show that preterm delivery is associated with retained placenta, but suggest that intrauterine infection and inflammation are not associated with retention. Other possible explanations are discussed. (Consumer Summary produced by Reliance Medical Information, Inc.)