Histologic chorioamnionitis, microbial infection, and prematurity.

The purpose of this study was to relate histologic chorioamnionitis to the isolation of microorganisms from the freshly separated chorioamnion in women who had early preterm delivery (before 35 weeks' gestation) following spontaneous labor. Histologic chorioamnionitis was identified in 51 of 95 study subjects. It was more common in the second trimester (72%) than from 27-34 weeks' gestation (33%) (P less than .001). Culture specimens were obtained for aerobic and anaerobic bacteria, yeasts, mycoplasmas, and Chlamydia. Microorganisms were recovered from 38 subjects; all culture reports were negative in 36. A statistically significant association was demonstrated between histologic chorioamnionitis and positive culture results. If any microorganism was recovered, 68% of the subjects had histologic chorioamnionitis, versus 39% if all cultures were negative. Of cases of histologic chorioamnionitis in the third trimester, 92% were associated with positive cultures, compared with 54% in the second trimester. Our results suggest that histologic chorioamnionitis is not synonymous with infection, especially in the second trimester.

The plasma renin-angiotensin system in preeclampsia: effects of magnesium sulfate.

Two groups of women were studied in a prospective longitudinal fashion to determine the effects of a 2.5-hour infusion of magnesium sulfate upon the renin-angiotensin system. Serum magnesium concentration, angiotensin-converting enzyme concentration, and plasma renin activity were measured at uniform intervals in women with either preeclampsia or preterm labor. Plasma renin activity was significantly lower (3.9 +/- 2.2 versus 6.1 +/- 1.8 ng/mL/minute; P = .004) and angiotensin-converting enzyme significantly higher (47.1 +/- 14 versus 34.0 +/- 10 U/mL; P = .008) in women with preeclampsia than in those with preterm labor. Magnesium infusion was associated with a sustained decline in plasma renin activity in preeclamptic women (P = .003). A transient decline in angiotensin-converting enzyme (P = .009) was observed in women with preeclampsia, but not with preterm labor. In contrast to the sustained change in plasma renin activity, angiotensin-converting enzyme concentration returned to baseline activity levels by 2.5 hours. A nonsignificant negative relationship (P = .06) was noted between angiotensin-converting enzyme and gestational age in subjects with preeclampsia. We conclude that a short-term infusion of magnesium sulfate leads to a sustained decline in plasma renin activity in preeclamptic women, but exerts no sustained effect on angiotensin-converting enzyme in women with either preeclampsia or preterm labor.