Your baby plans could be up in the air.
As millions of Americans brace for another day cloaked in wildfire smoke, experts are warning that the haze may be clouding more than the horizon — it could also affect couples’ chances of getting pregnant.
In one recent study, researchers found that when New Yorkers woke up to eerie orange skies in the summer of 2023, women undergoing IVF saw a steep decline in embryo transfer success rates.
The team analyzed 190 embryo transfers performed at a New York fertility center between June 1 and July 31, as smoke from massive Canadian wildfires descended on the state and sent New York City’s air quality levels plummeting.
For each procedure, the team looked at the local Air Quality Index (AQI) on the day of the embryo transfer, then compared pregnancy outcomes based on whether the air was considered good, moderate or unhealthy.
They also accounted for other factors that can influence IVF success, including the woman’s age and embryo quality.
What they found paints a troubling picture.
Tiny pollution particles could play a role
When air quality was considered good, about 62% of embryo transfers resulted in pregnancy. On days with moderate air quality, the rate was slightly higher at 65% — though researchers said the difference wasn’t statistically significant.
But when the AQI reached unhealthy levels — the kind of conditions seen during the worst wildfire smoke days — the pregnancy rate dropped to just 27%.
“We saw that even though the fires were not necessarily directly in our backyard, the smoke from so many miles away could have a negative impact,” study author Dr. Randi Goldman, attending physician and program director for the Reproductive Endocrinology and Infertility Fellowship Program at Northwell Fertility, told The Post.
“My hypothesis is that it doesn’t have to do with the actual lab itself or the transfer itself, but more in the days leading up to it and the days after it,” she said.
“The person who had that embryo transfer is then exposed to these potential environmental issues,” Goldman theorized, “and then it might be kind of that larger issue that’s contributing to the success rates.”
The study didn’t prove exactly why wildfire smoke may be linked to lower IVF success, but the researchers believe tiny pollution particles in the smoke could play a role.
Wildfire smoke contains microscopic particles known as PM2.5 that can travel deep into the lungs and enter the bloodstream. These particles are already known to pose health risks, and the study authors said they could potentially affect fertility by triggering inflammation and oxidative stress in the body.
The researchers wrote that it’s “biologically plausible” that short-term exposure to these particles could interfere with implantation, the crucial moment when an embryo attaches to the uterus.
“It’s important for anybody undergoing fertility treatment, [or any] reproductive health treatment, to think about this as something that’s important,” Goldman said.
How to reduce your risk during IVF treatment
While embryo transfers aren’t always possible to reschedule, the researchers said air quality could be another factor doctors and patients consider when planning treatment.
“On days on which AQI is particularly poor, one could consider embryo cryopreservation and defer embryo transfer to a future date when air quality is improved,” the study authors wrote.
Goldman also urged patients to reduce other environmental exposures before and after an embryo transfer.
“Nothing is going to come close to the negative impact of tobacco smoke and smoking cigarettes on outcomes,” she said. “And on days where air quality might be unhealthy — today is a really, really bad day in New York, for example — stay inside.”
For people who must go outdoors during periods of poor air quality, Goldman said a properly fitted KN95 mask may help reduce exposure. She also recommended using a high-quality HEPA air filter indoors.
“That would be very, very helpful because it’s really the ambient air around us that’s potentially having an impact,” she said. “We studied it only on the day of the embryo transfer itself, but the days before and the days after the embryo transfer probably have an impact, too.”
While the findings were notable, the study had some limitations. It involved only one fertility clinic, for example, and looked at a relatively small number of embryo transfers.
Still, Goldman said the findings highlight the need for more research into how air pollution may affect fertility.
“There needs to be more research on this topic. It’s not something that you hang your hat on. You never do that with a single study,” she said. “But I think it really starts the conversation for a potential modifiable factor that we have in the reproductive health world.”
The findings come as large parts of the country face another round of smoke drifting south from Canada and the Great Lakes region.
On Thursday, New York City’s air quality dipped below Delhi’s, reaching “very unhealthy” levels that “may cause health issues for everyone, especially sensitive groups.”
“Every New Yorker should take precautions,” Mayor Zohran Mamdani urged residents, advising them to stay indoors whenever possible and limit strenuous outdoor activities.
