INFERTILITY PREVALENCE

Prevalence of infertility judged higher than previous estimates, though studies vary greatly

A new study has found a 17.5% overall lifetime prevalence of infertility episodes.

Published 08 December 2022

How should infertility prevalence be measured to provide a truly reliable global and regional estimate? Arguably the most accepted definition is that of the World Health Organisation, which is based on not achieving pregnancy after 12 months or more of regular unprotected sex. However, other interpretations give much longer timeframes – and it’s this kind of disparity among others which gives rise to inconsistent and hard-to-compare data.

Now, the authors of a new meta-analysis and systematic review of more than 100 studies carried out over 20 years are calling for urgent reform in the definitions so that future research into infertility prevalence may lead to improved prevention, diagnosis and treatment.(1) Results from their review, which included every WHO region (the Americas, African, South-East Asia, European, Eastern Mediterranean, and Western Pacific), show high overall rates of lifetime and 12-month prevalence of infertility (17.5% and 12.6% respectively), but they also identified striking variations in study characteristics and methodological approach.

In a strongly worded message, the authors write that data collection and analysis must improve, and researchers must agree on a consistent definition for infertility prevalence to improve understanding at a global, regional and country-level and ‘our ability to help those who experience it.’

Key recommendations based on the results of this WHO-funded study include estimating infertility prevalence (standardised questions are needed), selecting methodologic approach (research objectives must be considered), reporting estimates (detailed methodological and analytical information is needed), and making comparisons across studies (compare estimates that are as similar as possible).

In developing countries alone, estimates for infertility prevalence range from 48.5 million couples to 186 million women who have been married. One of the most comprehensive analyses of infertility prevalence concluded that 1.9% of women exposed to the chance of pregnancy experienced primary infertility, and 10.5% experienced secondary infertility.

This long and complicated meta-analysis expands on previous studies by explicitly examining the variability across study characteristics. A total of 133 studies, published between January 1990 and March 2021, were included, with the vast majority cross-sectional in design. With more than a third (35%) from Europe, those selected had based their definition of infertility on the WHO and had to meet other criteria, including that the study reported estimates of the prevalence/cumulative incidence of infertility and was designed to be a representative sample of a general population of women and/or men.

Different methodological approaches used by the selected studies were categorised by the authors as prospective time to pregnancy (TTP), retrospective TTP, current duration, self-reported infertility (direct), constructed infertility (indirect), and undetermined. Period prevalence was defined as the proportion of individuals/couples with infertility at a specific point (eg, their first year after marriage), or over a time interval (eg, most recent pregnancy attempt within five years from the date of first interview); lifetime prevalence was described as the proportion of individuals/couples who have ever experienced infertility.

Results showed that ranges for lifetime (3.3-39.7%) and period estimates (1.6-34%) were similar and wide, even after accounting for methodological and study characteristics. Pooled estimates of lifetime and period prevalence were 17.5% and 12.6% respectively, with some variation in magnitude by region and methodological approach. For example, Western Pacific had the highest prevalence of lifetime infertility (23.2%), followed by the Americas (20%), Europe (16.5%) and Africa (13.1%). The lowest estimate was in Eastern Mediterranean (10.7%). The highest pooled estimate of period infertility prevalence was in the African region (16.4%), followed by Western Pacific (13%), European (12.4%), the Americas (10.4%), and Eastern Mediterranean (10%).
These results appear to contradict earlier studies, which have shown highest primary infertility prevalence in the North Africa/Middle East regions, and the highest secondary infertility prevalence rate in the Central/Eastern Europe and Central Asia regions.

However, the authors of this latest study explain that there was significant variation between the studies in the measures and definitions used to ascertain infertility prevalence. Some gave no upper limit for reproductive age while others did not report an age range at all; others restricted their sample to married couples or those in a union; the authors also found a few (n=10) focusing solely on men; and no 12-month or lifetime estimates were available for South-East Asia. The authors also noted their study was based on biologically-based infertility, not on social or conditional childlessness, which might reflect legal, regulatory or social constraints.

Infertility casts a long shadow over couples trying to conceive. Now, this latest analysis has identified gaps in the availability of studies for certain global regions and particular populations, and highlighted the need for accurate and comparable measures of the magnitude of infertility. Without these improvements, say the authors, the condition cannot be effectively addressed or managed.


1. Cox CM, Thoma ME, Tchangalova N, et al. Infertility prevalence and the methods of estimation from 1990 - 2021: a systematic review and meta-analysis. Hum Reprod Open 2022; https://doi.org/10.1093/hropen/hoac051
2. Mascarenhas MN, Flaxman SR, Boerma T, et al. National, regional, and 18 global trends in infertility prevalence since 1990: a systematic analysis of 277 health surveys. PLoS Med 2012; https://doi.org/10.1371/journal.pmed.1001356

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