NATURAL CONCEPTION

Meta-analysis finds one in five chance of natural conception after successful ART live birth

Meta-analysis finds one in five chance of natural conception after successful ART live birth

Published 03 July 2023

A meta-analysis of 11 ‘moderate quality’ studies finds that naturally conceived live birth after successful ART is ‘far from rare’ and contradicts the media message of miracle babies born to celebrity women after fertility treatment.

Naturally conceived childbirth is ‘far from rare’ in couples who have already had children by ART, according to results of a new meta-analysis.(1) Findings suggest that, ‘contrary to widely held views’, natural conception pregnancy may occur in ‘at least one in five women after having a baby via IVF or ICSI’. The authors somewhat sweepingly propose that ‘women seeking and undergoing fertility treatment are not absolutely nor permanently infertile’, findings which add a touch of realism to the myth of ‘miracle babies’ in the popular press.

The results were derived from a review of 11 eligible studies (‘of moderate quality’) which included more than 5000 women followed up from two to 15 years. However, as expected, the study designs (endpoints, duration, populations) were varied, making direct comparisons between them difficult. For example, the proportions of women having a natural pregnancy or live birth after an ART birth ranged from 12% to 33%, with a trend towards higher values in more recent studies. Similarly, studies included in the analysis found different variables associated with spontaneous conception after ART, including younger age (spontaneous pregnancy in 18% of women in the first three years after succsesful ART), shorter duration of subfertility, fewer number of treatment cycles prior to first delivery, and specific causes of subfertility - but no single specific factor was found to be universally significant in all studies. Even the cause of subfertility proved a ‘mixed picture’, with conception ‘more likely’ in endometriosis and unexplained infertility. With such limitations evident, the authors concede that ‘this meta-analysis can only give an indication of the likely incidence’ of naturally conceived live birth after ART.

A cohort study of ‘treatment-independent’ live birth following ART at a single UK centre described similar studies as ‘limited’ and mostly ‘based on surveys with poor response rates and limited sample sizes’.(2) This study, not unlike those of the latest meta-analysis, found after more than five years of follow-up a LBR of 17% in unsuccessfully treated women and 15% in those who had a live birth after ART.

Despite the limitations of the new meta-analysis, its authors suggest their results might be useful for counselling, either pre-treatment (expectant management?) or post-treatment (contraception?), and describe their pooled estimate of natural conception (0.20) as ‘robust’. Nevertheless, the overall character of the study is one of limitation and heterogeneity in its contributions, such that, say the authors, the pooled estimates are likely to be underestimates.

What of course may compromise further studies, they add, is today’s greater application of fertility treatments in sub-groups of women with no diagnosed cause of infertility (for example, singles and lesbian couples), and ‘who may cause the incidence of natural conception pregnancy after ART livebirth to increase further’.

The study did raise a little comment in the popular press, with one warning that, despite the high prevalence of pregnancies found after successful ART, there will still be some cases where conception is never possible naturally (severe male factor), and many others, especially when age dependent, rarely likely. In such cases, one expert told the BBC, ‘it would be advisable to seek treatment for a second child sooner rather than later’.



1. Thwaites A, Hall J, Barrett G, Stephenson J. How common is natural conception in women who have had a livebirth via assisted reproductive technology? Systematic review and meta-analysis. Hum Reprod 2023;
doi.org/10.1093/humrep/dead121
2. El Mokhallalati Y, Van Eekelen R, Bhattacharya S, McLernon DJ. Treatment-independent live birth after in-vitro fertilisation: a retrospective cohort study of 2,133 women. Hum Reprod 2019; 34: 1470–1478. doi.org/10.1093/humrep/dez099

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