Reversible contraception: Does it affect future fertility?

Key Points

Oral contraceptive pills

Many studies on oral contraceptive pills (OCPs) have found a short-term delay in the return to fertility, but no study has suggested long-term or permanent impairment.^4-7 This delay may be attributed to transient persistence of ovarian suppression, secondary to inhibition of gonadotropin secretion by estrogen and progestin. One of the first and largest studies, the Oxford-Family Planning Association (FPA) Study, included more than 17,000 women recruited from 1968 to 1974 who used OCPs (56%), a diaphragm (25%), or an intrauterine device (IUD; 19%).⁸ One of the first papers on this study, published in 1978, reported a significant delay in fertility of up to 42 months for nulliparous women and up to 30 months for multiparous women after discontinuation of an OCP. The return to fertility was measured as the time until delivery of an infant. A later publication in 1986 reported that 48 months after cessation of contraception, 17.9% of OCP users were undelivered versus 11.5% of those using a different contraceptive method.⁷ There was no association between duration of OCP use before discontinuation and fertility impairment.⁸

A separate case-control study differentiated OCP users by the same dosage groups while looking at the association between combined monophasic OCPs and primary infertility.¹ It did not find that infertile women were more likely to have taken OCPs with high estrogen doses than the controls. It did find that combined monophasic OCP use was associated with a lower risk of primary infertility.

There have been mixed results regarding the duration of OCP use and return to fertility.^4,6,7 Although the Oxford-FPA study and a nested case-control study from the Nurses' Health Study II found no association between increased duration of use and fertility, 2 other studies found the duration of use to be significant.^4,6,8,9

In the study by Hassan and Killick, 2,841 pregnant women in the United Kingdom completed questionnaires to evaluate the effect of commonly used contraceptives on subsequent fertility, measuring by time to pregnancy (TTP).⁴ They found the TTP to be 2-fold longer for long-term (>2 years) OCP use (8.2 months; 95% confidence interval [CI], 7.2-9.1) than long-term condom use (4.2 months; 95% CI, 2.5-6.1), and the TTP for short-term (<2 years) OCP use was similar (4.8 months; 95% CI, 4.2-5.4). These effects were found to be greater for older women, obese women, and women with menstrual disturbances. Although age may have become a larger issue with long-term use, it should have affected both the OCP and barrier groups equally.

Conversely, Farrow and associates found that prolonged OCP use (≥5 years) was associated with an increased proportion of conceptions within 1 year.⁹ These studies included OCP users who started the medication for contraception and cycle control, which could imply fertility issues. Many of these studies were of current pregnancies; therefore, those who failed to conceive were excluded.

Although most research has been done using the traditional 28-day cycle combination OCP, 2 recent studies examined a continuous regimen of levonorgestrel 90 mcg and ethinyl estradiol 20 mcg (LNG/EE).^10,11

One was a descriptive analysis after participation in a phase 3 contraceptive trial of 21 participants who left the trial to become pregnant. The pregnancy rate was 57% at 3 months, 81% at 12 months, and 86% at 13 months, with a median time of 4 months from OCP discontinuation to conception.¹⁰ These results are similar to the 12-month return to fertility rate in 2 of the aforementioned studies of cyclic OCPs (83.8% and 88%).^4,5

The other observational study report found that spontaneous menses or pregnancy occurred within 90 days of discontinuation for 185 of the 187 women (98.9%; 95% CI, 96.2-99.9).¹¹ Although these findings suggest no significant impairment of fertility after cessation of continuous OCPs, more research is needed about this method, as well as extended-cycle OCPs. There is no published evidence of delayed fertility with use of progestin-only pills.¹²