The possible preterm birth preventive effect of ampicillin during pregnancy

Objective: To study the possible association between oral ampicillin treatment during pregnancy and pregnancy complications, in addition to birth outcomes, particularly preterm birth. Methods: We evaluated newborn infants without congenital abnormalities born to mothers with or without ampicillin treatment during pregnancy in the population-based large data set of the Hungarian Case-Control Surveillance of Congenital Abnormalities. Results: Of 38,151 newborn infants, 2,630 (6.9%) had mothers with ampicillin treatment during pregnancy. Some pregnancy complications, particularly preeclampsia, showed a higher prevalence in pregnant women with ampicillin treatment. Mean gestational age was slightly longer (0.2 week) but it resulted in a significant reduction in the prevalence of preterm birth (7.1 vs 9.3%; adjusted POR with 95% CI: 0.8, 0.7–0.9). The preterm birth preventive effect of ampicillin was most obvious after the use of the drug in the first trimester of pregnancy. Similar difference was not seen in the reduction of low birth weight. The rate of preterm birth was lower in newborn infants born to mothers with acute infectious diseases of both the genitourinary and respiratory systems if they were treated by ampicillin. Conclusions: Ampicillin treatment, particularly in the first trimester of gestation, can reduce the proportion of preterm birth in pregnant women with acute infectious diseases of the genitourinary and respiratory system.