Natural conception after ART ‘far from rare’

3 minute read

New research suggests ‘miracle’ babies are more common you think.

One in five women go on to conceive naturally after a previous pregnancy using assisted reproductive technology, according to new research.

The use of ART, such as IVF, intracytoplasmic sperm injection or artificial intrauterine insemination, has become increasingly common in high-income countries over the past 40 years. Instances of women conceiving naturally after using ART, dubbed “miracle” pregnancies, have been reported in both medical and popular media.

But the findings of a new systematic review and meta-analysis involving 11 studies and over 5000 women who had previously conceived through ART, published in Human Reproduction, challenge commonly held beliefs that instances of natural conception after fertility treatment are few and far between.

“Our findings suggest natural pregnancy after having a baby by IVF is far from rare. 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,” said the study authors.

The proportion of natural pregnancies reported in individual studies varied from 12% to 33%, with researchers suggesting “an apparent trend towards higher values in more recent studies”.

When considering the 11 studies as a collective, 20% of women conceived naturally after a previously successful ART-enabled birth.

The sole Australian study included in the review reported the highest estimated proportion of natural pregnancies following an ART-enabled birth, which researchers concluded, “may be partially attributable to the accessibility of ART there at a relatively low cost”.

Dr Karin Hammarberg, senior research officer at the Victorian Assisted Reproductive Treatment Authority agreed Australians may “jump at” ART sooner than other countries due to treatments being more accessible in Australia compared to overseas.

“Therefore, [they] haven’t waited long enough and might have conceived without fertility treatment if they had waited,” she told The Medical Republic.

The use of ART is also more “culturally accepted” in Australia compared to other parts of the world, according to Dr Hammarberg.

Seven of the 11 studies found most natural conceptions occurred within the first two or three years following an ART-enabled birth. However, these findings are limited by the length of the follow-up periods used in each study.

Dr Shema Tariq, a London-based sexual health doctor, highlighted the importance of contraception after ART success.

“It took six rounds of IVF to conceive our son. My GP briefly mentioned contraception after he was born, but we both laughed and agreed it wasn’t relevant. I was 43 and had been told my chances of conceiving naturally were less than 1%,” she said in a statement.

“Eight months later I was unexpectedly, and naturally, pregnant with our daughter.”

The notion of fertility treatments increasing the odds of natural conception has been discussed for decades without being thoroughly investigated. While researchers identified several factors associated with spontaneous conception after ART, such as younger maternal age and fewer ART cycles before the birth of the first child, no factors were significantly associated with natural conception across all 11 studies.

“[Our daughter] has been the most wonderful surprise, but when we first found out I felt overwhelmed and unprepared for another pregnancy,” said Dr Tariq.

“If I’d known that one in five women conceive naturally after IVF, I’d have used contraception until I was ready both emotionally and physically”.

Dr Hammarberg echoed Dr Tariq’s sentiments while highlighting the challenges in preparing for an unexpected pregnancy.

“For example, taking folate is an important part of preparing for pregnancy – it’s too late to start taking it once you know you’re pregnant,” she said.

Human Reproduction 2023, online 20 June

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