Some antibiotics taken during pregnancy linked with major birth defects

20 Feb 2020

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Researchers have found a link between a type of antibiotic prescribed during pregnancy and an increased risk in major birth defects.

Data from more than 104,600 children born in the UK has shown that a type of antibiotic prescribed to women during early pregnancy could have major ramifications for the health of their future children.

Researchers from University College London (UCL) have published a study to BMJ that found an increased risk of birth defects among children whose mothers were prescribed macrolide antibiotics versus women prescribed penicillin.

Macrolide antibiotics – such as erythromycin, clarithromycin and azithromycin – are used for common bacterial infections, often as alternatives for those allergic to penicillin.

Previous studies found evidence for rare, but serious, side effects from macrolide use, especially in unborn children. As part of this study, the UCL team wanted to assess associations between macrolide antibiotics and major malformations, as well as four neurodevelopmental disorders including cerebral palsy and epilepsy.

This included analysing data from 104,605 children born in the UK between 1990 and 2016, with a median follow up of just under six years after birth. A further 82,314 children whose mothers were prescribed macrolides or penicillin before pregnancy and 53,735 children who were siblings of children in the study group acted as negative controls.

Major malformations were detected in 186 out of the 8,632 children whose mothers were prescribed macrolides at any stage during pregnancy and 1,666 of 95,973 children whose mothers were prescribed penicillin.

‘Should be used with caution’

Taking into account potential influential factors, macrolide prescribed in the first three months of pregnancy was associated with an increased risk of any major malformation compared with penicillin. No increased risks were seen when the antibiotic was taken later on in the pregnancy, during the second or third trimester.

However, a slight risk of genital malformations was found when macrolide was prescribed at any stage of pregnancy.

Addressing limitations of the study, the researchers said they were unable to examine treatment exposure during known critical periods for specific malformations and neurodevelopmental disorders. However, results were largely unchanged after further analyses, suggesting that the findings hold up.

If a causal association is there, the researchers estimated that an additional four children with cardiovascular issues would occur for every 1,000 children exposed to macrolides.

“These findings show that macrolides should be used with caution during pregnancy and if feasible alternative antibiotics should be prescribed until further research is available,” they wrote.

Colm Gorey was a senior journalist with Silicon Republic