No links have been found between taking prescription opioids or macrolide antibiotics during pregnancy and an increased risk of major birth defects, two new studies report today.
The observational studies, published by The BMJ, sought to address the inconsistency of previous research that reported associations between exposure to the drugs and some birth defects.
The first study examined data for more than 82,000 women in the USA, who received two or more prescriptions for any opioid during the first trimester of their pregnancy from 2000 to 2015.
After taking account of other potential risk factors, the researchers found no clinically meaningful increase in the risk of major birth defects overall, or in heart malformations, club foot or neural tube defects.
They found four to five additional cases of cleft palate per 10,000 pregnancies exposed to opioids in the first trimester and say patients should be made aware of this potential risk.
In the second study, researchers in Denmark compared data for nearly 1.2 million pregnancies from 1997 to 2016 and found no association between exposure to macrolides in early pregnancy and risk of major birth defects.
They found infants born with major birth defects occurred in 35 per 1,000 pregnancies exposed to macrolides compared with 37 per 1,000 pregnancies exposed to penicillin and 33 per 1000 unexposed pregnancies.
There was no change in results when they analysed further individual macrolides and specific birth defects according to organ systems. This, they say, suggests their findings are robust.
Although both studies are observational, the researchers say these were large studies using reliable medical insurance and national registry data, and they were able to account for a range of other risk factors that may have influenced the results.
Both research teams say their findings can reassure women about the risk of major birth defects if they are prescribed opioids or macrolide antibiotics during pregnancy.
Bateman BT, Hernandez-Diaz S, Straub L et al. Association of first trimester prescription opioid use with congenital malformations in the offspring: population based cohort study. The BMJ. February 2021. Doi: BMJ 2021;372:n102
Andersson NW, Olsen RH, Andersen JT. Association between use of macrolides in pregnancy and risk of major birth defects: nationwide, register based cohort study. The BMJ. February 2021. Doi: BMJ 2021;372:n107
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