More women than ever are carrying babies conceived with someone else’s egg—but few are told that this might carry greater health risks.

Pregnancies involving an embryo that doesn’t share the pregnant woman’s DNA are becoming more common. For many, it’s a path to parenthood that would otherwise be closed.

But emerging evidence suggests that these pregnancies may come with higher rates of complications, including pre-eclampsia, gestational diabetes and preterm birth, and that women are often not given the full picture before treatment.

As the fertility industry expands and diversifies, it’s time to ask whether patients are being adequately informed about the risks of carrying another woman’s egg—and whether more caution is needed in how these options are presented.

There are three situations in which a woman may carry another woman’s egg in her uterus.

The most common is when a woman cannot produce her own eggs but has a functioning uterus. In this case, donor eggs and in-vitro fertilization (IVF) offer the only route to pregnancy.

The other two situations involve fertile women carrying a donated egg on behalf of someone else. This happens in cases of gestational surrogacy, where a surrogate carries a baby genetically unrelated to her, or in reciprocal IVF, also known as ROPA or co-IVF. In the latter, one woman in a same-sex couple (or a trans man) donates her egg to her partner, so that both have a biological connection to the child.

In IVF, fertilization occurs outside the body and the resulting embryo is transferred into the uterus. But what happens when the egg in the uterus has no genetic similarity to the woman carrying it? Could this cause complications for her or the baby?

To answer that question, we need to compare outcomes in these situations to pregnancies where the egg shares approximately 50% of the mother”s DNA, either through natural conception or own-egg IVF. Early evidence suggests that having someone else’s egg in the uterus is associated with a higher risk of obstetric complications, including pre-eclampsia, gestational diabetes and preterm birth.

There are three key comparisons to make. First, donor-egg IVF vs. own-egg IVF. For infertile women using donor eggs, the most relevant comparison is IVF with their own eggs.

Second, gestational vs. traditional surrogacy. In gestational surrogacy, the surrogate carries a donor egg, while in traditional surrogacy, she uses her own. Outcomes can also be compared with the surrogate’s previous natural pregnancies.

Third, reciprocal IVF vs. own-egg IVF. In same-sex couples, reciprocal IVF can be compared to own-egg IVF to assess risks.

A review of 11 studies comparing donor-egg IVF to own-egg IVF found that donor-egg pregnancies had significantly higher rates of hypertensive disorders in the mother, as well as preterm birth and babies that were small for their gestational age.

A separate review focusing on pre-eclampsia in singleton IVF pregnancies found the condition occurred in 11.2% of donor-egg pregnancies, compared to 3.9% of own-egg pregnancies.

For women who can only become pregnant using a donor egg, these risks may be worth accepting. But it’s important that women are made aware of the potential complications, especially if carrying twins, which further increases risks.

Gestational surrogacy

With colleagues, I conducted a review of eight studies. The research suggests that gestational surrogacy (donor egg) is linked to higher rates of hypertensive disorders and gestational diabetes compared to traditional surrogacy (surrogate’s own egg) or previous natural pregnancies.

So why is gestational surrogacy often favored by clinicians and intended parents alike? For some doctors, it can offer greater medical and ethical clarity; for some parents, it can reduce legal and emotional complications. A common assumption is that genetically related surrogates may be more likely to want to keep the baby—but research shows this is not the case. Surrogates rarely seek to retain custody, regardless of genetic connection.

Evidence on reciprocal IVF is even more limited. A 2022 study of 21 women who underwent reciprocal IVF found that hypertensive disorders occurred in 23.8%, compared to 12.9% of the 62 heterosexual women using their own egg, and gestational diabetes occurred in 9.5% v 1.6%.

The only study directly comparing reciprocal IVF to own-egg IVF in same-sex female couples is an unpublished conference abstract, which found a higher miscarriage rate (19% v 14%), but reported no maternal or infant outcomes.

Despite limited data, fertility companies often market gestational surrogacy and reciprocal IVF as reasonably safe options. However, much of the research comes from clinicians affiliated with fertility clinics.

Crucially, there is still no strong evidence showing that fertile women carrying another woman’s egg have better outcomes than infertile women undergoing the same. But a lack of evidence is not the same as evidence of safety.

In some cases, pregnancy using one’s own egg may still be possible. For example, fertile women in same-sex couples may only need sperm donation to conceive naturally, rather than going through IVF.

Women deserve full, unbiased information about the risks. That includes knowing that carrying someone else’s egg may increase the likelihood of pregnancy complications. They can then make informed decisions about whether the potential benefits outweigh the risks.

This article is republished from The Conversation under a Creative Commons license. Read the original article.