The incidence of histological chorioamnionitis in IVF/GIFT preterm births.

A retrospective case control study was designed to investigate the role of subclinical infection as a risk factor for the high rate of preterm deliveries in IVF/GIFT pregnancies. The cases and the controls were identified from the records of consecutive livebirths of < 35 weeks' gestational age (GA), at King George V Hospital from 1987-1993. Fifty one singleton and 58 twin IVF/GIFT preterm births were matched for GA, year of birth, plurality, maternal age, parity, preclampsia and antepartum haemorrhage. As a marker of subclinical infection, the incidence of histological chorioamnionitis (HCA) in the 2 groups (as defined by the standardized, semiquantitative method of Benirschke) was compared. The matched variables did not differ significantly between the IVF/GIFT group and the control group. No significant difference in the incidence of HCA was detected between IVF/GIFT and control groups for singletons or twins. Overall 24% of IVF/GIFT and 30% of controls showed evidence of HCA, odds ratio (95% confidence intervals), 0.72 (0.40-1.31). This study showed no evidence that the incidence of HCA, is significantly increased in IVF/GIFT preterm births compared with other matched, preterm births. Therefore, we conclude that subclinical infection/inflammation cannot explain the 4-fold increase in preterm births in the IVF/GIFT population.