Injectable contraceptives associated with the longest delays in return of normal fertility

1. Injectable contraceptives were associated with the longest delays (2-8 menstrual cycles) in return of normal fertility, compared to other contraceptive methods.

2. No long-term and lasting effects on fecundability were associated with use of any of the studied contraceptive methods.

Evidence Rating Level: 2 (Good)

Fecundability is defined as the probability of pregnancy in a menstrual cycle without use of contraception. Current research on the association between contraceptive use and fecundability has been limited to the most common forms of contraception: condoms and oral contraceptives. However, the use of long acting reversible contraception is growing, with 13% of American women aged 25-34 using these methods in 2015-17. Therefore, the current prospective cohort study aimed to examine the relationship between contraception type and fecundability. The study population included 17,954 women (and their male partners) from Denmark and North America, with 10,729 pregnancies and 66,759 menstrual cycles. Data was collected on the most recent contraceptive used before trying to conceive, and the number of menstrual cycles without contraception before conceiving. The results found that 38% of participants used oral contraceptives, 31% used barrier methods (condoms, diaphragm, sponge, foam), and 13% used long-term reversible contraceptives. Injectable contraceptives had the largest association with lowered fecundability in comparison to barrier methods (fecundability ratio 0.65, 95% CI 0.47-0.89). In participants using injectable contraceptives, a short-term delay of 5 to 8 menstrual cycles was found before normal fertility returned, along with a 4 cycle delay for patch contraceptives, 3 cycle delay for oral and ring contraceptives, and 2 cycle delay for implants and hormonal or copper intrauterine devices. On average, other forms of contraception were not associated with decreased fecundability compared with barrier methods. Overall, this study showed that although injectable contraceptives appeared to have longer delays in fertility return, there are little to no lasting effects associating fecundability with any of these contraceptive methods.

Click to read the study in BMJ

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