Abstract
Around 8% of sexually active, fertile women wishing to delay or prevent pregnancy have an unmet need for modern family planning. While progestin-only contraceptive methods are highly effective, fear of infertility following use is a barrier to adoption. We conducted this narrative review with a systematic approach to summarise evidence on ‘return to fertility’, with the outcomes of return to ovulation, median or mean time to pregnancy, and pregnancy rates (ability to become pregnant within a year of method discontinuation) following progestin-only contraceptive discontinuation. We searched four databases (PubMed, CINAHL, Web of Science and The Cochrane Library) for any conference abstracts, original research articles or systematic reviews or meta-analyses published in English through 31 August 2023. We located 9 systematic reviews, 47 original research articles and 4 conference abstracts for oral contraception, injectables, hormonal intrauterine devices (IUDs) and implants. Oral contraception and hormonal IUD users return to ovulation and fertility sooner than injectable and implant users. However, by 1 year after discontinuation, pregnancy rates across methods are similar. While future fertility is a concern of potential modern contraceptive method users and healthcare providers, evidence suggests that individuals using progestin-only contraceptive methods may experience only slight delays in return to fertility following discontinuation and comparable . These results point to the need for continued and new efforts to provide communities with accurate information about contraceptives to dispel myths discouraging their use, and additional research using standard measurements.
Introduction
Progestin-only oral contraception, injectables, hormonal intrauterine devices (IUDs) and implants are powerful contraceptive methods that can empower individuals to limit or delay pregnancies.1 However, despite the effectiveness of these methods, an estimated 8% of women aged 15–49 years old around the world are considered to have an unmet need for modern contraception, which means they are capable of pregnancy, sexually active and want to prevent or space pregnancies.2 The reasons for non-use of modern contraception are manifold and include stock outs,3 4 various provider biases5 6 and cost.7 8
Another important barrier to the use of highly effective contraception is fear about side effects, including infertility following family planning method use. In a multicountry study in sub-Saharan Africa, 20%–40% of participants across sites believed that contraception would lead to difficulty becoming pregnant in the future.9 Further reinforcing the belief, a study in Kenya found that if an individual is unable to become pregnant after contraceptive use, the contraceptive use is identified as the cause of infertility.10 Likewise, a cross-sectional study in the USA found that 69% of surveyed female college students were concerned about the effect of contraception on their future fertility.11 Social media is amplifying these fears around hormonal method use.12 Hormonal methods may also mask underlying fertility issues; after discontinuing methods, previous users may attribute subfertility or infertility to contraceptive use instead of these other conditions.13 These fears are not limited to potential contraceptive users: providers often share these beliefs. Another study in the USA found that 23% of surveyed providers associated infertility risk with IUDs use.14 A qualitative study in Pakistan reported that providers were reluctant to provide IUDs to clients for this reason.15 While reasons for not using contraceptive methods are well-documented, the specific effects of these methods on return to fertility have not been systematically investigated.
There is reason to believe that infertility fears are unfounded and that fertility rapidly returns following discontinuation. Progestins prevent pregnancy through three main mechanisms.16 The first is the suppression of ovulation by acting on the hypothalamic–pituitary–ovarian (HPO) axis, which reduces luteinising hormone (LH) and follicle-stimulating hormone (FSH) secretion. The HPO axis is not damaged in this process, so after stopping the progestin, LH and FSH normalise, and ovulation can restart. Progestin-only methods also thicken cervical mucus, though the cervical glands are not altered permanently. When hormone levels fall, mucus returns to its thin, oestrogen-dominant state, allowing sperm penetration. Lastly, endometrial effects such as atrophy and reduced glandular activity prevent pregnancy, though, again, the endometrium is restored following discontinuation. Other effects, such as slowed tubal motility and impaired follicular maturation, are also reversible, as these are functional changes, not structural ones. The mechanisms of action of progestin contraceptives are reversible because no structural or cytotoxic changes occur in the reproductive organs, ovulation suppression is hormonal, not destructive, and the cervical mucus and endometrial changes depend on circulating hormone levels, so they can quickly reverse once progestin levels drop.
While previous reviews, published over 10 years ago, have summarised data on specific progestin-only contraceptive methods and their effect on return to fertility, we sought to provide an up-to-date review that allowed for comparisons across contraceptive methods and formulations.17 18 The objective of this narrative review is to provide additional summarised evidence on return to fertility following discontinuation of progestin-only oral contraception, injectables, hormonal IUDs and implants to support the dissemination of accurate data that can be used to inform counselling for individuals seeking out effective contraception.
Methods
This synthesis is part of a narrative review with a systematic approach that explored the association between five side effects and adverse outcomes and progestin-only contraceptive use (oral contraception, emergency contraception, injectables, hormonal IUDs and implants). In thisstudy, we present findings on return to ovulation, mean or median time to pregnancy and pregnancy rates following method discontinuation. The search protocol is registered on PROSPERO (#CRD42022337263c).19
Search strategy
We searched PubMed, CINAHL, Web of Science and The Cochrane Library for keywords for all progestin-only contraceptive methods and side effects and adverse outcomes of interest (see online supplemental material search terms).
Screening
We limited the results to conference abstracts, original research studies, meta-analyses and literature reviews in peer-reviewed journals or books with publication dates before August 2023 and in the English language. Two independent reviewers screened titles, one reviewer screened abstracts and full papers, and a second reviewer confirmed with a 5% sample of each. One reviewer extracted data into Excel with another 5% sample by a second reviewer. One individual reviewed the references for all items meeting our inclusion criteria and then we screened the list of possible additions in the same manner as items appearing in the original search. Experts on return to fertility following contraceptive method discontinuation contributed additional items to our synthesis.
Quality appraisal
We used the Mixed Methods Appraisal Tool 201820 to evaluate the quality of original research articles. The Mixed Methods Appraisal Tool 2018 appraises qualitative, mixed methods, quantitative descriptive, quantitative non-randomised and quantitative randomised controlled study designs with different criteria for each. There are seven criteria in the tool: two questions for all study types ask whether there are clear research questions and whether collected data allow researchers to answer the research questions. The other questions are specific to study type and cover biases, measurements and analysis. We weighed each criterion equally in our quality appraisal. One reviewer provided quality appraisal for each publication and a second reviewer confirmed the result for 5% of the publications. Differences were discussed and the reviewers jointly made decisions on ratings. Research items were high quality if they received a ‘yes’ for each response, medium quality if they received a ‘yes’ for five or six responses, and otherwise assigned low quality.
Outcomes and analysis
We evaluated the following outcomes related to ‘return to fertility’: return to ovulation, as defined by each publication’s authors, mean or median time to pregnancy, and pregnancy rates within a specified time period after contraceptive method discontinuation. We did not assess whether return to ovulation was associated with pregnancy. Among studies with a quantitative approach, we included those without comparisons to other groups, and ones that compared progestin-only contraceptive method users to other hormonal contraceptive method users and/or non-hormonal contraceptive users. In each sub-section for each contraceptive method, we first describe the overall study characteristics synthesised, followed by publications reporting on return to ovulation, then those that report on pregnancy rates (the ability to become pregnant within a specific timeframe). Whenever possible, we also synthesise findings related to the impact of user demographics on return to fertility.
In online supplemental materials tables 1-7, there is a column labelled ‘Significance and direction of effect’. In this column, we use ‘+’, ‘–’, ‘not significant’ and ‘not applicable’ to present findings. We use ‘–’ to clarify if the use of the contraceptive method had a statistically significant delaying effect on return to ovulation, mean or median time to pregnancy, or pregnancy rate compared with another group and ‘+’ to mark the opposite. A ‘ˆ’ refers to items with no comparison to other groups and therefore, without significance testing. The next column in these tables is ‘Magnitude of effect’, and lettered superscript links to footnotes that describe the comparison group and significance testing in greater detail. For items with results from more than one time point or time period, we separated the time periods by using commas in the ‘Duration’ and ‘Magnitude of effect’ columns. The study aim is pulled verbatim from the publication, wherever possible or paraphrased otherwise.
Patients or the public were not involved in the design, conduct, reporting, or dissemination plans of our research.
Results
For the broader review, we reviewed 24 723 titles, 1456 abstracts, 720 full papers and pulled 27 items from references: in this manuscript, we present results from 9 systematic reviews, 47 original research articles and 4 conference abstracts. We did not identify any items that captured results among emergency contraception users.
Oral contraceptives
We included one systematic review21 and three original research articles22–24 exploring progestin-only oral contraceptives and return to fertility. Of the three original research articles, there were two medium quality19 21 and one low quality20 paper. These consisted of two quantitative descriptive studies20 21 and one quantitative non-randomised study.22 The sole publication that reported on mean time to return to fertility following progestin-only oral contraceptive discontinuation is presented in online supplemental material table 1.
Return to ovulation
A study among individuals using levonorgestrel (LNG) 0.095 mg, 0.115 mg and 0.135 mg over 86 days of treatment reported that ovulation occurred an average of 15.5, 14.1 or 12.8 days after last treatment, respectively.22 A study among users of second, third (both combined oral contraceptives) and fourth generation (drosperinone-only) oral contraception found that drosperinone-only users had a longer return to ovulation compared with second generation oral contraceptive users.24
Median/mean time to pregnancy and pregnancy rates
Two items reported on mean time to pregnancy and pregnancy rates. A literature review stated that “… [there is] no information on the return of fertility from large-scale mini-pill studies… data from very small studies are reassuring”.21 Another study reported that discontinuing progestin-only pill users experienced a significantly longer mean time to pregnancy than condom users—5.3 months to pregnancy in the unadjusted model and 6.2 months to pregnancy in the adjusted model.23
Injectables
We identified 5 systematic reviews and meta-analyses,21 25–28 21 original research articles29–49 and 1 abstract50 exploring the effect of progestin-only injectables on return to fertility. We judged one to be high quality,30 thirteen to be medium quality29 31 33–35 37 39 41 42 45–48 and seven to be low quality.32 36 38 40 43 44 49 Our synthesis included fourteen quantitative descriptive studies,29 30 32 33 35 38 40–42 44 45 47–49 five quantitative non-randomised studies31 37 39 43 46 and two quantitative randomised controlled trials.34 36 Research items that explored mean or median time to pregnancy or pregnancy rates following progestin-only injectable discontinuation are summarised in online supplemental material table 2.
Return to ovulation
Several studies found that ovulation began again around the same time that individuals discontinuing other contraceptive methods started to report being pregnant, around 5 months postpresumed end of contraceptive protection. A study among individuals using subcuteneous depot medroxyprogesterone acetate (DMPA-SC) 300 mg, 150 mg, 104 mg x2, 105 mg, 75 mg or 45 mg reported that ovulation returned at a median 0.07 ng/mL MPA concentration.27 The estimated return to ovulation within 4 months of injection of 104 mg and 7 months of injection of 150 mg was under 2.2% in both cases—a second study on DMPA-SC found that ovulation was suppressed for 95.8% of participants for at least 112 days following injection.45 One small study of intramuscular depot medroxyprogesterone acetate (DMPA-IM) 150 mg discontinuers reported that subjects ovulated at 20–21 weeks (n=1), after week 25 (n=4), and after 33 weeks (n=3).42 A similarly small study reported that ovulation occurred at 7–9 months following DMPA-IM 150 mg injections in a cohort of three individuals.44 In a study using menstruation to identify ovulation, 48% of discontinuing DMPA-IM 150 mg users resumed regular bleeding within 9 months after their last injection, 52% resumed any bleeding within 6 months, and 68% conceived or established regular menstruation within 1 year29; this proportion increased to 84% at eighteen months. Two studies summarised in a book chapter found that among discontinuers, about half had normal menses return within 6 months after their last injection, while about one quarter were delayed for at least 1 year.25 Another study evaluating ovulation at 1 year postinjection reported that 94.7% of DMPA-IM users and 97.4% of DMPA-SC users had ovulated; their median return to ovulation (DMPA-IM: 183 days, DMPA-SC: 212 days) was not significantly different.36 A study comparing DMPA-IM doses found that increasing dosages did not necessarily translate into lengthier return to ovulation, though the study was limited to 20 participants at 25 mg, 50 mg, 100 mg and 150 mg who took, on average, 127 days, 165 days, 154 days and 180+ days (with only one person before 180 days) to ovulate after injection.34 Contrastingly, another small study found statistically significant delays in follicular function comparing groups with individuals who had received 25 mg, 50 mg, 100 mg and 150 mg doses of DMPA-IM.48
Several studies in a systematic review reported on ovulation following norethisterone enantate (NET-EN) 200 mg injection, with most reporting ovarian follicular activity within sixty days after last injection for at least some participants.21 Studies with different NET-EN doses (300 mg, 150 mg, 100 mg and 50 mg) found differing times to a significant rise in progesterone, signalling ovulation: 52–90+ days, 70–92 days, 70–90+ days, and 53–90+ days after injection, respectively.35 However, one study reported longer times to ovulation, with a median of 11 weeks postinjection in a cohort of fifteen individuals.46
A systematic review summarising time to ovulation following last injection reported that for the majority of discontinuing DMPA users, it took 15–49 weeks on average and 4.9–24.3 weeks for NET-EN 200 mg users.28 A study comparing the two progestin-only regimens found that the difference for return to ovulation was significantly later among DMPA users (5.5 months) than NET-EN users (2.6 months).43
Median/mean time to pregnancy and pregnancy rates
Several studies reported on median time to pregnancy and pregnancy rates for DMPA-IM 150 mg users and NET-EN 200 mg users. They found that DMPA and NET-EN users experienced similarly delayed return to fertility following discontinuation. Three publications related to two original studies among DMPA-IM 150 mg discontinuers reported median time to pregnancy 5.5–7 months after presumed end of contraceptive protection,21 38 40 while a fourth study reported a mean of 7.3 months to pregnancy after last injection.37 A study among NET-EN 200 mg discontinuers reported a mean 7.8 months to pregnancy after last injection.39 A final study reported a 9 months median time from DMPA-IM 150 mg discontinuation to pregnancy.31 The same study found that DMPA-IM 150 mg users were 4.82 times (adjusted OR) more likely to experience fertility delay of at least 1 year than implant, IUD and oral contraceptive users; 93.5% of previous DMPA users in the study did not return to fertility within a year after discontinuation.
Across six studies, 60%–76.8% of DMPA-IM 150 mg discontinuers reported pregnancy at 1 year after their last injection30 32 40 and 87%–89.4% in two studies at 2 years.32 37 Again, NET-EN 200 mg discontinuers experienced similar pregnancy rates, with 72.5%–77.5% of individuals in two studies reporting pregnancy at 1 year after their last injection.39 41
One abstract evaluating data from a retrospective cohort of 500 and prospective cohort of 470 DMPA-IM 150 mg users reported that return to fertility after discontinuation was similar to individuals who had previously used oral contraceptives, IUDs and no contraception.50 Items that explored pregnancy rates following progestin-only injectable discontinuation are summarised in online supplemental material table 3.
User demographics
Two studies on weight and return to fertility did not report definitive results. One study explored the use of LNG butanoate 20 mg and 40 mg, an investigational contraceptive formulation, and found that 13/14 users returned to fertility before 6 months.33 The earliest ovulation was in day 77 for two obese individuals: one person receiving 20 mg and one receiving 40 mg. The longest delay in return to fertility was 206 days in a normal body mass index individual receiving 40 mg. Mean LNG level at time of ovulation was at approximately 47 pg/mL, the lower limit of assay detection, and no normal body mass index subjects had ovulation before 88 days, which was a significant finding. One systematic review reported that weight was not associated with return to fertility among DMPA-SC 104 mg users in two studies.26
The duration of use of injectables does not appear to affect return to fertility. A study in Thailand found a non-significant relationship between DMPA-IM 150 mg duration of use and pregnancy rate among six individuals.49 Another study of former DMPA-IM 150 mg and 400 mg users also detected no direct relationship between total dosage, number of injections, months of usage and return to menstruation after discontinuation.40 A study investigating NET-EN 200 mg use likewise found no relationship between number of injections and time to pregnancy.41 In a study looking at both DMPA-IM 150 mg users and NET-EN 200 mg users, researchers reported no correlation between duration of exposure and delayed return to ovarian function.43
Hormonal IUDs
We synthesised three systematic reviews and meta-analyses,26 51 52 nine original research articles23 53–60 and four conference abstracts61–64 exploring return to fertility after use of the hormonal IUD. Of the original research articles, three were considered low quality,23 56 60 three medium quality54 55 57 and three high quality.53 58 59 The original research articles included five quantitative descriptive studies23 53 54 58 59 and four quantitative randomised controlled trials.55–57 60 No studies in our synthesis explored return to ovulation. Items that reported on mean time to pregnancy following hormonal IUD use are summarised in online supplemental material table 4.
Median/mean time to pregnancy and pregnancy rates
At 1 year, greater than 75% of users in thirteen studies of different hormonal IUD dosages were able to conceive. One of the only items that included measurements at less than 1 year reported that at 1 month, 3 months and 1 year, 8.4%, 35.8% and 80.0% of previous hormonal IUD 52 mg users conceived.61 The authors of this abstract noted that median LNG levels were not significantly different among individuals who conceived within 3 months and those who conceived at 4–12 months following hormonal IUD discontinuation. Two other studies found similarly high levels of pregnancy following discontinuation: in one study at 1 month, 3 months, 6 months and 1 year, 14.7%, 42.6%, 65.4% and 96.4% of previous hormonal IUD 52 mg users conceived. In the other, at 1 month, 6 months and 1 year, 19%, 71.4% and 80.9% of hormonal IUD users conceived.54
A study on return to spontaneous menses found that 99.7% (342/343) individuals menstruated within 3 months of discontinuing a hormonal IUD 52 mg.63 Median time to pregnancy was 95 days, and 70.0% of individuals conceived within 6 months, 88.3% within 1 year. A third study reported that 70.6% of individuals became pregnant within 6 months and 86.8% within 1 year.58 The median time to pregnancy was 4 months. A third study reported that former hormonal IUD 52 mg users took 1.4 months to pregnancy after discontinuation.23 However, one study reporting on 21 former hormonal IUD users reported that the longest time to pregnancy after discontinuation was 29 months.54
In one study that reported 86.1% of previous hormonal IUD 52 mg users becoming pregnant within 1 year, the authors reported a median time to pregnancy of 92 days.53 A meta-analysis of data from three countries found that individuals took about two menstrual cycles to return to fertility following unspecified hormonal IUD discontinuation.52
A literature review synthesising five studies found that pregnancy rates were similar among former hormonal IUD users, other former long-acting reversible contraception users and individuals not using contraception.51 Only one study compared Norplant and Norplant II implant users to hormonal IUD users and reported non-significant differences in pregnancy at 2 years following contraceptive method discontinuation.55 A third study reported that for individuals using a method in the short term (<2 years) or longer term (2+ years), there was no significant difference in pregnancy rates between condom and hormonal IUD users.23 Research items that reported on pregnancy outcomes following progestin-only hormonal IUD discontinuation are summarised in online supplemental material table 5.
User demographics
Several studies explored the impact of weight, genetics, medications and other factors on hormonal IUD use and return to fertility but did not come to any conclusive findings.
A 2-year study on former hormonal IUD users found that parity was not significantly associated with mean/median time to pregnancy or pregnancy rate following discontinuation, but that there was a positive, non-significant relationship between longer duration of use and pregnancy.55 Another study found that parity was not associated with pregnancy among hormonal IUD 13.5 mg and 19.5 mg users.57 Similarly, a study reported that time to pregnancy did not differ between parous and nulliparous individuals after hormonal IUD 52 mg discontinuation.63 Another two studies confirmed that parity and body mass index did not affect pregnancy after discontinuation,61 nor did parity or gravidity.62
Two other items reporting on weight and pregnancy following method discontinuation found conflicting results. One systematic review found that weight was not associated with return to fertility among hormonal IUD use in two studies.26 A second study among hormonal IUD 52 mg users reported that after discontinuation, only obesity was associated with ability to conceive.53
Implants
We identified two systematic reviews65 66 and nineteen original research articles23 31 37 55 67–81 investigating return to fertility after progestin-only implant use. Of the original research articles, we considered three to be low quality,23 78 81 11 medium quality31 37 55 68 69 71 74 75 77 79 80 and five high quality.67 70 72 73 82 They included thirteen quantitative descriptive studies,23 67–70 73–78 80 81 five quantitative non-randomised studies31 37 71 72 79 and one randomised controlled trial.55
Return to ovulation
Several studies investigated return to ovulation, finding it to be swift among former progestin-only implant users. A study of 10 individuals discontinuing LNG implant 216 mg reported that the first evidence of ovulation was 3 days following implant removal and the last individual ovulated 47 days following removal.78 Among former etonogestrel (ENG) implant 68 mg users, various studies reported on return to ovulation : >90% of participants within 3 weeks in one study,65 for 40% of participants in 1 month in another study,75 and 86% of former users experienced menses within 3 months in a third study.67
Median/mean time to pregnancy and pregnancy rates
Several studies investigated time to pregnancy following progestin-only implant discontinuation—these studies found that the ability to conceive occurred almost immediately following implant removal. One study found that 39% of individuals became pregnant after early implant removal during the study period; pregnancy took 1 week to 31 months, with a mean of 9 months; only one pregnancy out of thirteen was intentional.73 Four additional items reported mean and median times to pregnancy: one study among LNG implant 150 mg users found that the median time to pregnancy following discontinuation was 3 months,68 while a similar study reported a mean of 6.9 months,37 and third and fourth studies of unspecified implants reported 4 months, with a significantly smaller proportion of implant users experiencing delayed return to fertility (greater than 1 year) compared with DMPA users,31 and 10.6 months to pregnancy, which was significantly higher than among condom users in both unadjusted and adjusted models.23
Studies among former ENG implant 68 mg users reported that in fourteen days post-discontinuation, 12% became pregnant;66 at 3 months, 13.8%–29.16%,67 69 75 66.66% at 9 months75 and 95.8% at 1 year.75 Among discontinuing LNG implant 150mg users, at 1 month 20% became pregnant,81 77.7% at 3 months,70 76 82 63.4%–77.7% at 6 months,70 76 81 82 77.7%–80.3% at 1 year70 76 81 82 and 88.3%–94.4% at 2 years.55 70 76 81 82 Researchers reported similar numbers among LNG implant 216 mg users, with 76.5%–86.5% of discontinuers becoming pregnant at 1 year37 77 79 and 87%–95.2% at 2 years.37 79 A 1-year study among unspecified implant users reported that 70% became pregnant a year after discontinuation.83 Studies that explored pregnancy outcomes following progestin-only implant use that we included in our synthesis are summarised in online supplemental material table 6. Items that reported on mean/median time to pregnancy following progestin-only implant use that we included in our synthesis are summarised in online supplemental material table 7.
User demographics
A few studies investigated parity, duration of use, weight/body mass index, medication use and implant insertion technique and their impact on return to ovulation and fertility. One study reported that there were no significant differences in time to pregnancy or pregnancy rates between individuals who had used an LNG implant 150 mg for <2 years or 2+ years.81 In Chile, a quantitative non-randomised study found that length of use and time to pregnancy were not related: individuals using the implant for longer than 5 years had similar chances of pregnancy within 6 months as individuals exposed to the implant for less than 5 years.79 Lastly, a study reported that longer duration of LNG implant 150 mg and 216 mg use was correlated with higher pregnancy rates, but the results were not significant.55 Three studies reported a non-significant negative relationship between ENG or LNG level and time to fertility, that individuals with higher hormone levels had extended return to fertility compared to other contraceptive method users.71 72 80 In a study among LNG implant 150 mg and 216 mg users, there were non-significant associations between parity and time to pregnancy.55
A study among postabortion LNG implant 216mg users reported on two discontinuations for pregnancy: these individuals conceived 9.5 and 12.5 months following implant removal.74
Discussion
The results of our narrative review demonstrate that there is a delay in return to fertility following progestin-only contraceptive method use. Despite relatively scarce evidence—nine systematic reviews, 48 original research articles and four conference abstracts—for oral contraception, injectables, hormonal IUDs and implants, the association between progestin-only contraceptive use and delayed return to fertility is clear. Hormonal IUD users appear to return to fertility first, but the evidence demonstrates that by 1 year, comparable proportions of individuals using oral contraception, injectables, hormonal IUDs and implants conceived. The evidence is clear: pregnancy rates at one year of discontinuation among former progestin-only contraceptive users are similar to pregnancy rates at one year of discontinuation of former users of other contraceptive methods.84
There are two important implications of this narrative review. First, due to the relatively common misconception by potential progestin-only family planning users that these methods may cause future infertility, programmes that distribute these methods should provide essential information to communities to dispel myths that may prevent contraceptive use. Second, there are research gaps that may be filled. There are relatively few studies, and almost all with small study sizes, that investigate return to fertility following contraceptive discontinuation and researchers in the field do not appear to use standardised measurements for ovulation and fertility. The employment of conventional, agreed on metrics for ovulation and fertility, including when to start measuring discontinuation, whether the day of last injection, pill or method removal, or following the supposed end of contraceptive effect, would allow for meta-analyses to better capture large-scale return to ovulation and fertility across populations.
Limitations
We decided to conduct a narrative review with a systematic approach on this topic due to the importance of disseminating evidence in a reasonable time frame to influence future research and programming and to capture as much evidence as possible in our searches. Because of this and our decision to exclude items not in English, we may have missed important literature published in other time periods and in other languages, leading to geographic or demographic biases. Our quality appraisal revealed that we were able to identify research of good quality. However, due to our decision to use the Mixed Methods Appraisal Tool for quality appraisal, we were unable to grade conference abstracts and literature reviews. This may have affected our findings, but the majority of the literature included is from original research articles. As is the case with all literature reviews, studies with null findings are often not published, which may bias findings, though in this case, this would likely lead to us finding a weaker association in the literature. Study limitations, such as the use of small sample sizes, retrospective designs or self-reported return to fertility outcomes may also have affected our results. Finally, the results of this narrative review should be understood in the context of infertility research; there are many well-defined and studied factors, including genetics and the environment, for example, that may affect an individual’s ability to become pregnant other than previous use of a contraceptive method.85 Despite the limitations of this narrative review, we believe that this is a strong contribution to the field in furthering our understanding of the impact of progestin-only contraceptive methods on return to fertility.
Conclusions
The evidence that we summarised in this narrative review demonstrates the fertility-delaying effect of progestin-only contraceptive methods after discontinuation, in particular, for injectables and implants. The data on other methods, such as progestin-only oral contraceptive and hormonal IUD users, showed a rapid return to fertility after discontinuation. We did not find any evidence supporting the idea that use of these methods leads to infertility. The results of this narrative review point to the need for additional research with standardised measurements and accurate contraceptive method information to be shared to dispel myths and misconceptions, whether that is through individualised accurate contraceptive counselling, large-scale campaigns, or other means, to ensure that people capable of pregnancy can make informed and empowered decisions about their health.
