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Doxylamine during pregnancy: minimise dose and duration, due to possible link with malformations

FEATURED REVIEW Prescrire's analyses have for many years found doxylamine to be the first-choice antiemetic drug in early pregnancy, when non-pharmacological measures fail. A recent study suggests an increased risk of major birth defects. Does this finding affect doxylamine's harm-benefit balance and its place as the first-choice drug for relieving nausea and vomiting during pregnancy?
Full review (3 pages) available for download by subscribers.


  • In 2019, a cohort study conducted in Quebec, Canada, including about 45 000 children exposed to the combination of doxylamine + pyridoxine during the first trimester of pregnancy for an average of 4 weeks, showed a roughly 7% increase in the incidence of major birth defects and a roughly twofold increase in spina bifida, compared with children not exposed in utero to an antiemetic drug. Despite the methodological precautions taken by the study's authors, a risk of bias exists.
  • No particular risk was identified in meta-analyses of earlier, less highly powered studies. A number of case-control studies have shown associations with specific malformations, including spina bifida, pyloric stenosis, and congenital heart defects.
  • In practice, when non-pharmacological measures are insufficient for relieving non-serious but very troublesome vomiting during pregnancy, doxylamine remains the first-choice antiemetic drug, in the absence of a better alternative. It is important to inform the patient of the concerns over the risk of malformations and the lack of a less dangerous alternative drug, and to determine, in conjunction with the patient, the lowest possible daily dose and the shortest possible treatment duration that provide acceptable relief. 

©Prescrire 1 November 2020

Source: "Doxylamine during pregnancy: minimise dose and duration, due to possible link with malformations" Prescrire International 2020; 29 (220): 267-269. Subscribers only.

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See also:

"Severe vomiting with
dehydration during pregnancy.
Antiemetics have little place"
Prescrire Int 2020;
29 (212): 48-49.
Pdf, subscribers only

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