A new study shows women who used oral contraceptives for more than five years before attempting to conceive are more likely to have success within six months or a year than women who have never used the pills or took them for a shorter period of time.
Researchers looked at nearly 8,500 planned pregnancies among couples in England during the 1990s. The pregnant women and their partners answered questionnaires about various factors that might have affected their fertility, such as use of birth control pills, age, whether they smoked or drank alcohol, their educational level, height, and weight.
The study found that the longer the women used birth control pills, the more likely they were to become pregnant within six months or a year of stopping use of the pills.
75.4% of the women who had been on the pill for more than five years conceived within six months of trying compared to 70.5% of women who had never used the pill. A similar advantage was found among long-term pill users who took up to a year to become pregnant compared to non-users (89.5% vs. 85.4%).
Although some previous research has suggested that using oral contraceptives may reduce fertility, researchers say those studies only looked at fertility immediately after stopping pill usage. Other studies have shown fertility returns to normal levels within three months, and this study backs up those findings.
Researchers say long-term pill users had the same fertility advantage whether they had previously had a child or not.
Researcher Alexandra Farrow, PhD, of the department of Health and Social Care at Brunel University in Isleworth, UK, and colleagues say prolonged use of birth control pills may have a protective effect on fertility by reducing the damaging effects of endometriosis and improving iron stores in women.
Other factors that were associated with a delay in conceiving in the study were the age of both the man and the woman, the woman's exposure to cigarette smoke, her level of education and her BMI (body mass index, a measure of weight in relationship to height).
The findings appear in the October issue of the journal Human Reproduction.