Use of antibiotics during pregnancy and risk of spontaneous abortion

After adjustment for confounders, use of macrolides, quinolones, tetracyclines, sulfonamides and metronidazole during pregnancy was associated with increased risk of spontaneous abortion. Similar results were found when penicillins or cephalosporins were used as comparator groups

This was a nested case–control study (n=182,369) within the Quebec Pregnancy Cohort (1998–2009) which matched each case with ten random controls for gestational age and year of pregnancy. Spontaneous abortion was defined as having a diagnosis or procedure related to spontaneous abortion before the 20th week of pregnancy. Use of antibiotics (filed prescriptions) was compared with non-exposure and exposure to penicillins or cephalosporins.

Although the study included a large sample, confounding by infection severity is a potential limitation. Other potential confounders were not available in the Quebec Pregnancy Cohort, including smoking status, folic acid use, alcohol intake, body mass index and other dietary factors