The contraceptive pill has no link to the chance of a baby being born with a birth defect, a groundbreaking international study has revealed.
More than 800,000 births across Denmark were tracked over five years, with one in 12 women taking the pill less than three months before they became pregnant, and one in 100 continuing to take the pill during their pregnancy.
Neither of these groups reported any increase in babies born with defects relating to limbs, the heart, urinary tract anomalies, and organs that develop outside the body.
Researchers reported that the rate of major birth defects per 1000 births was consistent irrelevant of whether the women took the pill or when she stopped taking it: 25.1 birth defects were recorded from women who had never taken the pill; 24.9 for those who took the pill at least three months prior to pregnancy and 24.8 for those who continued to take the pill.
Overall, 2.5 per cent of live births recorded were of a baby with a physical abnormality.
It disproves a long-standing uncertainty as to whether the pill can cause abnormalities in fetal development. The pill is the most popular form of contraception for women across the world, and when taken correctly, has a 99 per cent effectiveness rate.
Kathleen McNamee, medical director of Family Planning Victoria, said the "robust" study would reassure women that they can safely take the pill and not worry about any potential impact on their future offspring.
"Sometimes women are worried about the baby when they conceive while they're on the pill, so it's good to get such evidence so we can say 'yes, it's perfectly safe'."
Ms McNamee said there has been some misinformation in the past about the pill and its possible impact on fetuses.
Researchers said: "Women who have a breakthrough pregnancy during oral contraceptive use or even [those who] intentionally become pregnant within a few months of stopping oral contraceptive use [because] any exposure is unlikely to cause her fetus to develop a major birth defect".
The study, led by Harvard University, was published in British Medical Journal. It is the first major study on how sex hormones found in the pill impact fetal development.
Of the women whose child's birth was recorded, 68 per cent used the pill but stopped at least three months before becoming pregnant, 21 per cent never used the pill, 8 per cent stopped taking the pill less than three months before becoming pregnant and 1 per cent continued taking the contraceptive.