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About 20% Women Become Pregnant Naturally After Conceiving With IVF

Becoming pregnant naturally after having a baby conceived with assisted reproductive technology (ART) is "far from rare", said researchers, who found this happens for 1 in 5 women.

Infertility is estimated to affect 1 in 7 heterosexual couples, with a woman becoming pregnant naturally after fertility treatment having been typically considered 'rare', explained the authors of a new study, published in the journal Human Reproduction. However, the researchers, from University College London (UCL), pointed out that it is "not in fact an unusual event".

Most Conceived Naturally Within 3 Years

For the study, the researchers searched Ovid Medline, Embase, and PsycINFO databases for studies published between 1980 to 24 September 2021. They performed a systematic review with meta-analysis of the data obtained from 11 studies of over 5180 women around the world to evaluate how common it was to become pregnant naturally after having a baby conceived by fertility treatment.

The researchers found that the proportions of women who had a natural conception pregnancy or livebirth after a fertility treatment livebirth ranged from 12-33%, with an "apparent trend towards higher values in more recent studies". This figure remained unchanged, even when taking into account the different types and outcome of fertility treatment, alongside length of follow up, they highlighted.

"Given the significant heterogeneity between studies, a random-effects meta-analysis was used to produce a pooled effect estimate of the incidence of natural conception pregnancy after ART livebirth of 0.20 (95% CI 0.17 to 0.22)," explained the authors.

Most of the included studies (7 out of 11) found that the majority of the natural conception pregnancies occurred within the first 2-3 years after in-vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) livebirth, the authors said.

Natural Conception After Fertility Treatment Not a Rare Phenomenon

It was "widely known" that some women having babies via ART went on to conceive naturally, highlighted the authors. "This reproductive history is of media interest and often described as 'miracle' pregnancies," they pointed out.

"The finding that natural conception pregnancy occurs in 1 in 5 women after having a baby via ART contradicts the media message that this is a rare phenomenon," challenged the authors.

Dr Annette Thwaites, from the UCL EGA Institute for Women's Health and lead author, said the study findings suggested that natural pregnancy after having a baby by IVF was "far from rare". She added: "This is in contrast with widely held views – by women and health professionals – and those commonly expressed in the media, that it is a highly unlikely event."

The authors acknowledged some limitations of the study, which included the small number of studies, their individual limitations and differences in population, type of ART, outcome measure, and follow-up. This meant, they stressed, that it was difficult to make direct comparisons, and that the meta-analysis could only give an indication of the likely incidence based on the current published evidence.

Women Empowered to Plan Their Families

"Many women may not realise that they could conceive naturally following fertility treatment," the authors pointed out, and cautioned that this could lead to them becoming pregnant again quickly or when they aren't ready, which could be problematic for both the health of the mother and child."

Commenting for Medscape News UK, Dr Raj Mathur, British Fertility Society chair, and spokesperson for the Royal College of Obstetricians and Gynaecologists, said: "With more people than ever accessing fertility treatment, this is important research to inform conversations between doctors, women, and people about fertility treatment, and their choices following successful treatment. More research needs to take place to explore the factors which influence natural conception post fertility treatment and understand if it is to do with the fertility treatment itself or other factors."

It was important for those who had had successful IVF to know how likely they are to conceive naturally afterwards, stressed the authors, who hoped that the information gleaned from the study findings would be used to counsel people considering their options after successful fertility treatment.

National, data-linked studies were needed, the authors said, to provide more accurate estimates of the incidence of natural pregnancy after conception through ART, and analysis of associated factors and trends over time, to facilitate tailored counselling of couples considering further ART.

"Knowing what is possible would empower women to plan their families and make informed choices regarding further fertility treatment and/or contraception," underlined Dr Thwaites.

Funding for the study was provided by the National Institute for Health Research. The authors declared no conflicts of interests.