Beta-lactam antibiotics during pregnancy: a cross-sectional comparative study Zagreb-Novi Sad

During pregnancy, a number of changes occur in women's body, and some medications are safe and some are not. The aim of our study was to establish the possible correlation between use of beta-lactam antibiotics in pregnancy and occurrence of congenital malformations.

The study included 893 pregnant women from Zagreb and 6099 pregnant women from Novi Sad. 527 pregnant women used beta-lactams. First part of the study (one month study) was performed at four maternity hospitals in Zagreb, Croatia. Second part were collected as a part of the study analysing the teratogenicity of drugs used in pregnancy, a longitudinal study performed in Novi Sad district.

Pregnant women most frequently used antibacterial agents in the first trimester of pregnancy. They used 15 different antibacterial medications, most often beta-lactams. In Zagreb arm, out of the total number of pregnant women that used medications during pregnancy (859), 231 (26.9%) used beta-lactam antibiotics. Malformations were detected in 8 (3.5%) cases. The prevalence of malformations in newborns whose mothers did not take beta-lactam antibiotics in pregnancy (662) was 2.7% (18 newborns with malformations). In Novi Sad arm, out of the total number of pregnant women that used medications during pregnancy (2013), 296 (14.7%) used beta-lactam antibiotics. Malformations were detected in 14 (4.7%) cases. The prevalence of malformations in newborns whose mothers did not take beta-lactam antibiotics in pregnancy (5803) was 1.7% (99 newborns with malformations).

The results show possible teratogenic potential even with those antibacterials which are considered safe (amoxicillin) but as those are usually minor malformations they often pass undetected. International pharmacoepidemiological studies of drug use in pregnancy could substantially contribute to the improvement of pharmacotherapy, and could be of great help in assessing the fetal risks.