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Oral contraceptives ‘not linked to major birth defects’

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Oral contraceptive use just before or during pregnancy is not associated with an increased risk of major birth defects, suggest latest study findings.

The researchers noted that, when planning a pregnancy, most women stopped using oral contraceptives, which contain sex hormones.

“We observed no increased risk of any major birth defect associated with oral contraceptive exposure just before or during pregnancy”

Study authors

But they highlighted that little was previously known about any links with birth defects, especially among women who became pregnant while still taking them or after recently stopping use.

The US and Danish researchers carried out a large observational study to examine oral contraceptive use around the time of conception and into pregnancy, and any potential links with major birth defects.

They looked at data on 880,694 infants, 2.5% of whom had a major birth defect – for example, an orofacial cleft or limb defect – within the first year of life.

Infants with birth defects with known causes, such as foetal alcohol syndrome, or chromosomal aberrations, were excluded.

Recent oral contraceptive use less than three months before the pregnancy or use during early pregnancy was analysed, based on prescription information.

In total, 68% of mothers used oral contraceptives, but stopped more than three months before pregnancy and 21% never used oral contraceptives.

Overall, 8% recently stopped using oral contraceptives within 0-3 months before pregnancy, and 1% used oral contraceptives beyond pregnancy – both categories were analysed as exposed.

After adjusting for other known risk factors, the study revealed no increased risk of any major birth defect associated with oral contraceptive exposure, said the researchers in the British Medical Journal.

The prevalence of major birth defects per 1,000 births was consistent across each group:

  • 25.1 for never users
  • 25.0 for oral contraceptive use more than three months before pregnancy
  • 24.9 for oral contraceptive use within 0-3 months before pregnancy
  • 24.8% for oral contraceptive use after pregnancy

The researchers noted that their study was observational, so no definitive conclusions could be made about cause and effect.

However, they stated: “We did not observe a significantly increased risk of major birth defects associated with oral contraceptive use in the months before or after pregnancy onset.

“For women who have a breakthrough pregnancy during oral contraceptive use or even intentionally become pregnant within a few months of stopping oral contraceptive use, any exposure is unlikely to cause her fetus to develop a major birth defect,” they said.

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