Does evidence of inflammation on Papanicolaou smears of pregnant women predict preterm labor and delivery?

BACKGROUND Preterm delivery is the most common cause of neonatal morbidity and mortality in the United States. There is evidence that cervicovaginal infection could predispose to preterm labor. This study explored a possible association of evidence of inflammation on an otherwise normal Papanicolaou smear obtained during pregnancy with subsequent preterm labor and preterm delivery. METHODS Using a retrospective matched cohort design, we studied women who gave birth to live singleton infants at the University of Missouri Hospital and Clinics during a 21-month period. Papanicolaou smears were obtained from 1 to 8 months before delivery and were interpreted in the same cytopathology laboratory. Data pertaining to outcome variables and potential confounding variables were collected from hospital charts. RESULTS Incidence rates were 14.4 percent for labor < 37 weeks' gestation (preterm labor), 12.3 percent for hospitalization for preterm labor, 9.9 percent for delivery < 37 weeks (preterm delivery), 2.6 percent for delivery < 34 weeks, and 7.5 percent for birth weight < 2500 g. On univariate and multivariate analyses, there were no significant differences in any outcome between the 293 women with inflammation and the 284 women without inflammation on Papanicolaou smear. Results were unchanged when the analysis was limited to the 412 women who received no antibiotics during pregnancy. Among the 38 women with a history of preterm labor or preterm delivery, those with cervical inflammation had a higher rate of preterm labor than those without inflammation. CONCLUSIONS In the sample as a whole, there was little evidence that findings of inflammation on Papanicolaou smear constituted a risk factor for preterm labor or preterm delivery. The data suggest that inflammation could be associated with an increased risk in a subgroup of women at higher risk by virtue of their obstetric history.