according to a new prospective cohort study.
Women who used hormonal intrauterine devices, copper intrauterine devices, and implants had the shortest delays, based on the same research project, which involved analyzing data from approximately 18,000 women in North America and Denmark.
“Most research on the use of contraceptives and fertility has focused on the effect of oral contraceptives on fecundability,” and data on the association between fertility and other contraceptive methods are limited, wrote Jennifer J. Yland, MS, of Boston University School of Public Health and colleagues.
“Given the increasing popularity of long acting reversible contraceptive methods and other alternatives to oral contraceptives, more research into their short- and long-term effects on fertility is needed,” the researchers noted.
In the study, which was published in the BMJ, the researchers reviewed data from a total of 17,954 women from three cohort studies of individuals planning pregnancies between 2007 and 2019. Participants reported their contraceptive use and typical menstrual cycle at baseline, then responded to questionnaires every 2 months for up to a year or until pregnancy.
On average, users of injectable contraceptives had the longest delay in return of normal fertility (five to eight menstrual cycles), compared with four cycles for patch contraceptives, three cycles for oral and ring contraceptives, and two cycles for hormonal and copper intrauterine devices and implants.
A total of 10,729 pregnancies were reported within 66,759 menstrual cycles; approximately 77% of the women conceived within 12 months, and 56% conceived within 6 months.
Oral contraceptives were the most common method of contraception (38%), followed by barrier methods (31%), natural methods (15%), and long-acting reversible contraceptives (13%). Intrauterine devices were the most frequently used of long-acting reversible contraceptives (8% hormonal, 4% copper).
The time until fertility returned after discontinuing contraceptives was not associated with duration of contraceptive use.
The study findings were limited by several factors including the potential misclassification of menstrual cycles and the use of self-reports for the time of contraceptive discontinuation, especially for users of injectable contraceptives, the researchers noted.
However, the results were strengthened by the large study size and show “little or no lasting effect” of long-term use of any of the reported contraceptive methods on fertility, the researchers noted. “Understanding the comparative effects of different contraceptives on fecundity is essential for family planning, counseling for contraception, and management of infertility,” they said.
Comparison of contraceptives can inform counseling
The study is important because the use of long-acting reversible contraceptive (LARC) methods (IUDs, implants, patches, and injectable contraceptives) has become increasingly common worldwide, corresponding author Jennifer J. Yland, MS, said in an interview. “Many women are concerned about the potential effects of contraception on future fertility. However, previous research on this topic has focused mostly on oral contraceptives,” she said.
Ms. Yland said that the findings on oral and injectable contraceptives were consistent with previous publications. However, “we were surprised to find that women who had recently used the hormonal IUD had a shorter time to pregnancy, compared with women who used barrier methods,” she said.
The take-home message for clinicians is that delays in the return to normal fertility were temporary for all hormonal contraceptive methods, Ms. Yland emphasized. “However, delays in the return of fertility after discontinuing certain hormonal methods, such as injectables, were considerably longer than that shown for oral contraceptives. These findings should be taken into account when women are considering contraceptive choice in the context of family planning and infertility management,” she noted.
“Future research should evaluate the potential associations between recent use of hormonal contraceptives and perinatal outcomes,” she added.