The Alabama Preterm Birth Study: Intrauterine infection and placental histologic findings in preterm births of males and females less than 32 weeks

Objective

The objective of the study was to determine whether there are differences in the placental histology and various markers of infection/inflammation between preterm male and female fetuses.

Study design

The placentas and umbilical cords of 446 infants born at 23 to 32 weeks were examined histologically, cultured for aerobic and anaerobic bacteria and mycoplasmas, and the interleukin-6 levels in cord blood determined.

Results

Male infants were significantly more likely to have positive placental cultures than female infants (63.4% versus 51.8%, P = .01, odds ratio 1.5, 1.0 to 2.4). Cord blood Mycoplasma hominis and Ureaplasma urealyticum infections were marginally more common in male than female fetuses (27.6% versus 19.2%, P = .06, odds ratio 1.7, 0.9 to 2.9), but cord blood interleukin-6 levels were not different between male and female fetuses. The only significant histologic difference between male and female placentas was in decidual lymphoplasmacytic cell infiltration (6.3% versus 0.9%, P = .003, odds ratio 8.3, 1.8 to 39.0). Males had a higher percentage of decidual lymphohistiocytic cell infiltration, but the differences were not significant (11.3% versus 7.4%, P = .160, odds ratio 1.6, 0.8 to 3.2).

Conclusion

Male infants were significantly more likely to have positive placental membrane cultures than female infants. Decidual lymphoplasmacytic cell infiltrations were more common in male versus female placentas, confirming a previous observation and suggesting that a maternal immune reaction to fetal tissue may be more common in male fetuses.

Key words: Infant sex, Preterm birth, Placental histology, Placental infection