Large registry study implicates ‘infertility-related factors’, not treatment, in adverse birth outcomes after ART

Published 16 April 2023

A study cross-linking Swedish registries has compared adverse birth outcomes in ART-treated lesbian couples (thus without an infertility indication) with those of heterosexual couples conceiving naturally and with ART; the lesbian pregnancies had ‘more favourable’ birth outcomes.

A cross-linking registry study from Sweden which compared birth outcomes from natural and ART pregnancies with those of same-sex lesbian couples has found lower rates of adverse outcomes among the lesbian couples, suggesting, say the authors, ‘that infertility-related factors rather than reproductive treatments contribute to higher rates of adverse birth outcomes in ART pregnancies’.(1) The results confirm what some previous studies have indicated, but are now confirmed in a treated but not infertile population and with the strength of large population numbers: 868 ART births among same-sex lesbian couples, 23,488 ART births among heterosexual couples, and 456,898 naturally conceived births. Many studies in the past have usually compared ART outcomes with natural conceptions, and attributed any elevated risk of poor outcome to multiplicity, though some have tried to tease out the contribution of infertility or its treatment - ‘the chicken or the egg?’ as one review asked.(2)

The treatment of same-sex lesbian couples with ART (IVF, ICSI and IUI all with donor sperm) has emerged over the past two decades as an example of applying techniques designed for infertile couples to a non-infertile population. Results, in these couples without an infertility indication, are largely good. In recent years, some clinics have introduced a ‘shared motherhood’ programme in which one partner provides the egg for fertilisation (with donor sperm) and the other carries the pregnancy.(3)

In the present study results from the Swedish birth registries were cross-checked with four adverse outcomes: birth weight; gestational age; low birth weight (<2500 g); and preterm delivery (<37 weeks of gestation). Results were adjusted for multiplicity and maternal age - and for means of conception. Almost every ART birth among heterosexual couples was conceived via IVF/ICSI, but only two-thirds in same-sex couples, who, said the authors, ‘often start treatments with IUI, which has a lower chance of success regardless of subfertility’.

Results showed, first, that ART-conceived births in both same-sex and heterosexual couples showed a higher rate of multiplicity (5.8% and 7.5%) than naturally conceived births (2.1%). Second, couples who conceived naturally had significantly lower birth weight and gestational age and similar risk of preterm delivery as same-sex couples conceiving with ART, indicating, said the authors, that same-sex lesbian couples having ART had more favourable or similar birth outcomes to heterosexual couples conceiving naturally or with ART. This, they concluded, would suggest that ‘infertility-related factors rather than reproductive treatments contribute to higher rates of adverse birth outcomes in ART pregnancies’.

The ‘chicken or egg’ review of Bersten et al failed to draw any firm explanatory conclusions on the short and long-term health risks associated with ART pregnancies (‘both the chicken and the egg matter’), though they did acknowledge that the risks are ‘modest’ and that singletons born after ART are more likely to have adverse perinatal outcomes than spontaneously conceived singletons.(2) The review did recognise the distinctions suggested by fresh and frozen embryo transfers (a higher risk of small for gestational age babies, low birthweight and preterm birth with the former, and an increased risk of large for gestational age and pre-eclampsia with the latter). The review concluded that separating the contribution of infertility from that of ART treatment is ‘challenging’ and would require ‘appropriate control groups’; birth outcomes from lesbian couples (without infertility) treated with ART would seem to offer a reasonable group to compare with infertile heterosexual couples also treated with ART.

1. Goisis A, Cederström A, Martikainen P. Birth outcomes following assisted reproductive technology conception among same-sex lesbian couples vs natural conception
and assisted reproductive technology conception among heterosexual couples. JAMA 2023; 329: 1117-1119.
2. Berntsen S, Söderström-Anttila V, Wennerholm U, et al. The health of children conceived by ART: ‘the chicken or the egg?’. Hum Reprod Update 2019; 25: 137–158.
3. Bodri D, Nair S, Gill A, et al. Shared motherhood IVF: high delivery rates in a large study of treatments for lesbian couples using partner-donated eggs. Reprod Biomed Online 2018; 36: 130–136.

Get notified of new articles with our ESHRE newsletter.

Sign up and never miss an update