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NATURAL CONCEPTION

One in six couples conceive spontaneously after unsuccessful ART

Published 24 September 2019

A cohort study which followed-up more than 2000 IVF patients in a single fertility centre found that 17% conceived spontaneously after unsuccessful ART and 15% after successful treatment.

Around one in six couples (17%) who have been unsuccessful with IVF or ICSI will go on to have a baby, according to a population-based retrospective cohort study.(1) The rate was found to be slightly lower (15%) but similar for those whose fertility treatment had previously been successful.

This first comprehensive study into 'treatment-independent' live birth rates and influencing factors was based on data from more than 2000 British women having ART at a single centre. Findings show that younger women and those who had been trying to become pregnant for a relatively short time have the greatest chance of conceiving, independent of the fertility treatment they receive.

The authors from the University of Aberdeen in Scotland say the research will help clinicians provide couples with an indication of their likely chance of parenthood - both for those remaining childless after treatment and others who were successful but want another baby. They recommend that those counselling infertile women include this information when IVF or ICSI has ended given that the likelihood of natural conception starts to peak in the first few years post fertility treatment.

'Our results will help clinicians counsel infertile couples on the characteristics associated with a live birth after a failed or successful IVF outcome,' said co-author David McLernon from the University of Aberdeen.

Current evidence on pregnancy from conception after ART and its associated factors is limited. A French study in 2016 found that around 17% and 24% of women conceived spontaneously after failed or successful treatment respectively.(2) Dutch research on almost 1000 couples referred to a single centre found that spontaneous pregnancies occurred in 28% of all couples, and there were 32% 'treatment-dependent' pregnancies; women with unexplained infertility had a better prognosis of wait-and-see conception than those whose inability to conceive was attributed to other causes.(3)

However, studies carried out to date have largely been based on small sample sizes, a short duration of follow-up, or on surveys with poor response rates. Thus, say the Aberdeen authors, it has been difficult to determine the accurate chance of a pregnancy independent of fertility treatment or the clinical factors which affect this outcome.

Their study included 2133 women who all had IVF between 1998 and 2011 at the Aberdeen Assisted Reproduction Unit. Around half (n=1060) had achieved a live birth following successful IVF or ICSI, and the rest (n=1073) had either had no pregnancy or pregnancy loss. The two groups were followed from the date of the last embryo transfer until either the first treatment-independent live birth, or end December 2012 (whichever came first). The primary outcome was the spontaneous live birth rate at one, two-and-a-half, five and ten years of follow-up.

Results showed a 17% live birth rate independent of treatment and within five years of follow-up for patients who were unsuccessful with this ART, 15% for those who had previously conceived successfully with ART.

A shorter duration of infertility, younger female age and IVF in both groups were associated with a higher chance of a naturally-conceived baby. The chance of a post-IVF birth was reduced in cases of tubal factor in unsuccessfully treated women, and for three or more previous IVF/ICSI transfers for those in the successful group. ICSI was also associated with a decreased chance of natural conception post-treatment in both groups even after accounting for cause of fertility, possibly, suggest the authors, because clinicians chose ICSI for couples with a relatively poor prognosis.

The researchers say their study provides a better understanding of the long-term prognosis of treatment-independent live birth and associated factors. However, among its limitations is a lack of data on the women's use of contraception or active attempts to get pregnant. Both factors, they point out, could have influenced the live birth rates outside fertility treatment.

1. El Mokhallalati1 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.

2. Troude P, Santin G, Guibert J, et al. Seven out of 10 couples treated by IVF achieve parenthood following either treatment, natural conception or adoption. Reprod Biomed Online 2016; 33: 560-567.

3. Donckers J, Evers J, Land J. The long-term outcome of 946 consecutive couples visiting a fertility clinic in 2001–2003. Fertil Steril 2011; 96: 160-164.