Antibiotic use during pregnancy has been much discussed. Could we finally have a definitive answer?
Thousands of pregnant women across America are prescribed antibiotics during their term; around 4 out of 10 expectant mothers will use them at some point during their pregnancy.
Along with penicillin, macrolide antibiotics are the most commonly used medications in the general population, including pregnant women.
Macrolides are a group of drugs, generally antibiotics, which include erythromycin, fidaxomicin, azithromycin and clarithromycin. They have a slightly wider antimicrobial spectrum than penicillin and can be used in cases where a penicillin allergy is present.
The current study was led by Anick Bérard, PhD, of the University of Montreal in Canda and its affiliated CHU Sainte-Justine Children's Hospital, and Hedvig Nordeng, of the University of Oslo in Norway.
The team looked at macrolides and their potential adverse pregnancy outcomes, including birth defects. Bérard says:
"With penicillin, macrolides are amongst the most used medications in the general population and in pregnancy. However, debate remained on whether it is the infections or, in fact, the macrolides used to treat them that put women and their unborn child at greater risk of adverse pregnancy outcomes, including birth defects."
Previous investigations into macrolide safety during pregnancy have produced contradictory results. Some studies have claimed an association between macrolides and cardiovascular malformations. Other studies have drawn links between the use of macrolides during pregnancy and an elevated chance of epilepsy and/or cerebral palsy.
These findings and others in the same vein have led to an avoidance of prescribing macrolides to pregnant women in several Scandinavian countries.
The Quebec Pregnancy Cohort
For the present study, the research team poured over survey data from the Quebec Pregnancy Cohort (QPC); this cohort was set up by Bérard by combining four administrative databases in Quebec province.
The QPC is one of the biggest cohorts of its type in the world, and between 1998 and 2009, information regarding 290,000 pregnancies was collected.
Information on health outcomes for mother and child are stored, along with information regarding lifestyle variables, socio-demographic information, weight and height at the beginning of the pregnancy, weight gain during pregnancy, natural health product use, folic acid intake and data regarding pregnancy history.
The Food and Drug Administration (FDA) and Health Canada do not permit the inclusion of pregnant women in clinical trials assessing drug efficacy; consequently, data on the safety of drug exposure during pregnancy before the medication goes to market are scarce. In this regard, the QPC is invaluable.
For this particular research, information on the mother's use of pharmaceuticals - azithromycin and clarithromycin - was retrieved from Quebec's public pharmaceutical insurance program. This data was then compared with the use of penicillin, which is a well-tolerated and well-studied antibiotic.
From the cohort, 135,839 pregnancies met the criteria for inclusion in the study. Of these, 1.7% involved exposure to the macrolides during the first trimester, while 9.8% of pregnancies resulted in the child having a major congenital malformation.
Bérard explains the results:
"After statistical analysis, we found no meaningful association between the groups compared to penicillin use. We aimed to estimate the risk of major congenital malformations after fetal exposure to the two most commonly used macrolides, and failed to find any."
Bérard believes that the reason for previous confusion about macrolide safety may have stemmed from the medical issues they were prescribed to treat. For example, the macrolide azithromycin is often used to treat chlamydia infections. Chlamidya itself can cause birth defects. When this is combined with a scarcity of data, false positives are easily created.
For any expectant mothers currently taking macrolide antibiotics, a collective sigh of relief appears to be warranted. Bérard, however, does add a note of caution, explaining that more obscure antibiotics - which are less frequently prescribed - still need further investigation.
Written by Tim Newman