What We Don’t Know About I.V.F.

And why there’s still a staggering lack of data for doctors to reference.

Credit...Eleanor Davis

This story was originally published on Dec. 17, 2019 on NYT Parenting.

You would think that after 40 years, we would know what the long-term effects are for the women who undergo I.V.F. and similar procedures to promote pregnancy. In the United States, more than 55,000 women give birth to a baby conceived through assisted reproductive technologies (A.R.T.) every year. Twelve percent of American women age 15 to 44 — 7.3 million of them — have received medical care for infertility. A third of American adults now say that they have used fertility treatments or know someone who has. But there are still large gaps in our knowledge about how these procedures affect women years down the road. Why?

[What to know about I.V.F.]

Part of the problem is a dearth of follow-up data, especially in our fragmented American health system, which lacks national medical records. Most existing research has been able to compare only the postpregnancy health of women who have conceived using fertility treatments with that of those who did not. “But, of course, that crude comparison is not comparing apples to apples,” says Dr. Natalie Dayan, an obstetric internist and assistant professor of medicine at McGill University. “It’s comparing women with infertility who have tried multiple times and then became pregnant through A.R.T. and women who conceived naturally.” So it’s all but impossible to know which observed health risks are due to the fertility treatments and which are a result of the underlying cause of the infertility itself.

Assisted reproduction is also constantly evolving. “By the time you go years out from the procedure, the procedures have changed, dramatically,” says Judy Stern, a professor of obstetrics and gynecology and pathology at Dartmouth. For example, in the last few years, there has been a shift toward trying to implant embryos that were previously frozen (rather than never frozen), after data emerged showing that babies born from frozen transfers had higher birth weights. But Stern’s team found an increased risk of respiratory, blood-related and brain abnormalities for the children when frozen embryos are used, and other researchers have found higher risks of pre-eclampsia for the women. It’s also not yet well understood how the health outcomes associated with traditional I.V.F. methods compare with those related to intracytoplasmic sperm injection (ICSI), in which a single sperm is injected into an egg. ICSI was intended to be used only in cases of male-factor infertility but is now used in two-thirds of I.V.F. cycles in the United States.

Another difficulty arises when subsets of patients are treated alike even when they’re not. The health risks to women who freeze or donate their eggs has been extrapolated from research on I.V.F. patients — but egg donors are young and healthy, unlike most women undergoing I.V.F., who tend to be much older. Egg donors are also typically given higher amounts of hormones to stimulate the production of eggs, and some undergo the procedure several times. “We have no idea what this level of hormonal stimulation at this time in a woman’s life might be doing to her body,” says Linda Kahn, a postdoctoral fellow in pediatrics at the New York University School of Medicine.

As more and more women turn to A.R.T. to conceive — and increasingly do so at older ages, which itself comes with greater pregnancy risks — experts say we need more information to help them better weigh the likelihood of a successful pregnancy against the likelihood of a serious health complication. “People have focused much more on the kids,” Stern says. “There’s less information on the women. What we really don’t know is whether or not anything that’s going on in those pregnancies — like the placental problems and hypertension — has long-term influences.” Part of the future of fertility will lie in developing new procedures and techniques — but part of it lies in better understanding the technologies we already employ.

[The truth about pregnancy over 40]

Maya Dusenbery is a journalist and author of Doing Harm: The Truth About How Bad Medicine and Lazy Science Leave Women Dismissed, Misdiagnosed, and Sick.