Surrogates have double the chance of dangerous pregnancy complications such as high blood pressure and heavy bleeding compared to natural mothers, a study suggests.
Canadian researchers looked at the records of nearly one million births and found that although babies born through surrogacy are no worse off, their birth mothers were at risk of health problems.
Around seven per cent of surrogates suffered severe complications, compared with just 2.4 per cent of women with natural conceptions and 4.6 per cent of people undergoing in vitro fertilisation (IVF).
Researchers are unsure what is causing the effect, but say that carrying someone else’s child may bring “physical and psychological impacts”.
Marina Ivanova, study author from Queen’s University, in Kingston, Canada, said: “There are several potential mechanisms that might explain the increased risk of severe maternal morbidity among gestational carriers (surrogates).
“These include differences in baseline health or socio-demographic characteristics of those who choose to become gestational carriers, potential differences in prenatal care and monitoring, the physiological and psychological impact associated with carrying a pregnancy for another person, as well as the effects of the treatments used during the IVF process.”
Surrogacy is legal in Britain, but is not legally enforceable, so a birth mother cannot be forced to give up a child. It is also illegal to pay a woman anything more than reasonable expenses.
The number of parents having a baby using a surrogate in England and Wales has almost quadrupled in the last 10 years. Parental orders, which transfer legal parentage from the surrogate, rose from 117 in 2011 to 435 in 2021.
The new findings showed that one in seven surrogates suffered postpartum haemorrhages (heavy bleeds after birth) compared with just one in 17 women who had conceived naturally.
Likewise, one in seven surrogates had high blood pressure disorders compared with just one in 15 unassisted conceptions.
In both cases, IVF treatment also had a higher risk of complications, but not as high as surrogacy.
Because surrogates must undergo IVF, it is likely that assisted reproduction is adding to some of the risk, but researchers said it did not account for all of it.
Dr Maria Velez, study supervisor and senior author said: “[Surrogates] were also less likely to be in the highest income bracket, and we know that lower socio-economic status is associated with higher serious maternal morbidity rates.
“However, sociodemographic characteristics were accounted for in the analysis, and the results were similar, which suggest potential different mechanisms.”
Despite the elevated risk, the study did not find any significant difference in health outcomes for babies.
The research was presented at the European Society of Human Reproduction and Embryology (ESHRE) annual meeting in Amsterdam, and the results published in the journal Human Reproduction.
