Can We Predict Our Ability to Conceive?
Can We Predict Our Ability to Conceive?
For more than a decade, researchers for Boston University’s Pregnancy Study Online (PRESTO) have been uncovering lifestyle, environmental, and medical factors that may affect people’s chances of conceiving and having successful pregnancies.
After a brief uptick during the COVID-19 pandemic, the birth rate in the United States resumed its decades-long decline in 2023, dropping by three percent in 2023 to the lowest rate in a century.
Many experts attribute this decline to educational, economic, and social factors that have slowed teen birth rates and prompted a growing trend in delayed childrearing until older ages.
But, too often, people who actively try to conceive encounter obstacle after obstacle, and what should be the start of a joyous time turns into a frustrating and emotional experience.
For more than a decade, researchers for Pregnancy Study Online (PRESTO) at the School of Public Health have uncovered lifestyle, environmental, and medical factors that may affect fertility and pregnancy outcomes. The web-based preconception cohort study is the largest of its kind worldwide, following thousands of individuals ages 21-45 who are trying to conceive.
Its goal: to identify modifiable changes that may increase one’s chances of conceiving and having a successful pregnancy.
“In one of our first PRESTO papers we examined age as a predictor of fertility and found that around age 32 or 33, there is a noticeable drop in the chances of conception for females,” says Lauren Wise, professor of epidemiology and PRESTO lead investigator. “We still see that age-related fertility decline today, so as pregnancy planners age, it’s important to share practical changes that they can make to improve their chances of natural conception.”
Wise launched PRESTO in 2013 with Kenneth Rothman, professor of epidemiology, and Elizabeth Hatch, adjunct professor of epidemiology who retired this year from her full-time position. Funded by the National Institutes of Health, PRESTO spurred from its Danish counterpart, Snart Foraeldre (“soon parents”), which the professors launched in 2006. Female-identifying participants in every state and all Canadian provinces are invited to complete questionnaires for one year (or until they conceive) about their diet, exercise, medication use, sexual activity, stress levels, and other factors, with the option for their male partners to enroll. They can also opt to use fertility tracking apps.
The team of faculty investigators, postdoctoral associates, masters-level research fellows, and doctoral student researchers have published dozens of findings, among them: higher intake of trans fats and sugar-sweetened beverages, as well as current smoking, were linked to lower fecundability (per-cycle probability of conception), but caffeine was not; and taking folic acid supplements increased fecundability. Male partners’ cannabis use was strongly associated with increased miscarriage risk. Moderate alcohol use and the HPV vaccine during the preconception period appear to pose no fertility risks.
Danes seem to have slightly higher fecundability than Americans, despite studies that suggest Danish males have lower sperm counts, Hatch says. The team hasn’t formally explored this finding, but she wonders if this difference reflects the different social and lifestyle factors between the two countries.
“Compared to Americans, Danes’ perceived stress is lower, they exercise more, their education and healthcare are paid for,” says Hatch, who was principal investigator of the Danish component. “Society is much more level there, while inequality in America is enormous, and getting worse.”
Because of PRESTO’s flexible design, we had the ability to answer in a way that I don’t think anyone else really could.
US inequality was on stark display during the COVID-19 pandemic, but the global crisis enabled PRESTO researchers to refute rampant misinformation on COVID-19 vaccines. Coinvestigator Amelia Wesselink (SPH’18), research assistant professor of epidemiology, and researchers added COVID-related questions to the surveys and quickly published an analysis showing that vaccines do not cause infertility—a finding that earned a mention on Saturday Night Live’s “Weekend Update”.
“We were able to immediately address a pressing public health question,” says Wesselink, who has been a part of PRESTO since its inception while she was an epidemiology doctoral student. “Because of PRESTO’s flexible web-based design, we had the ability to answer this question in a way that I don’t think anyone else really could.”
As climate change worsens, PRESTO researchers are also analyzing how the environment affects reproductive health. Wesselink leads projects examining the impacts of air pollution and heat on fertility and miscarriage, finding in a 2022 study that miscarriage risk increases during hotter seasons. She also serves as coinvestigator of the E-PRESTO substudy, for which researchers collect participants’ blood and urine samples in the clinic and by mail to assess individual health risks based on environmental contaminants. In collaboration with Silent Spring Institute, Wesselink designed a “report-back” website where participants receive results from their blood and urine tests, learn how their chemical levels compare with other cohort members and the general population, and receive information about ways to reduce their exposure.
This work also represents PRESTO’s shift in recent years to structural and neighborhood-level factors that shape reproductive health. Coinvestigator Mary Willis, assistant professor of epidemiology, has published studies that suggest living in socieconomically disadvantaged neighborhoods is linked to reductions in fertility, and that exposure to residential green space slightly increases one’s chances of becoming pregnant. Her research has also identified potential challenges for data collection and health research in a post-Roe era; Willis led a study earlier this year that found that PRESTO participants who lived in states where abortion was banned or severely restricted were less likely to share personal health information in the fertility tracking app that PRESTO offers.
“Generating multi-pronged epidemiologic evidence is a key step towards figuring out what options may yield policy that could protect population health,” says Willis, who is the first BU faculty member to receive NIH’s Early Independence Award, in which she is studying the effects of oil and gas development on reproductive health.
“I’m hoping to redefine what stress means in the context of the built and social environment, and its effect on health.”
Doctoral students are an integral part of PRESTO, driving much of the study’s cutting-edge research. Willis collaborates with and mentors Sharonda Lovett, a PhD candidate in epidemiology who received an SPH pilot grant this year to study the impact of residential segregation on fertility. These pilot funds will be used to compile and annotate a spatial-temporal dataset of several neighborhood exposures. Lovett is also leading work on individual-level stressors, including adverse childhood experiences and discrimination.
“I’m hoping to redefine what stress means in the context of the built and social environment, and its effect on health,” Lovett says.
Chad Coleman (SPH’17, ’25), a recent graduate of the PhD program in epidemiology, is making strides on his dissertation work pertaining to sleep quality and reproductive health, analyzing Fitbit data from participants to examine how the amount and quality of sleep affect various outcomes. Early analyses indicate that participants with more fragmented sleep have slightly greater difficulty conceiving.
“I really enjoy my sleep work because it presents modifiable public health interventions that can be implemented to improve sleep and increase the chances of conception,” Coleman says.
In a presidential election year largely defined by significant federal and statewide restrictions on reproductive rights, being able to make informed decisions about family planning is critically important. PRESTO is charging ahead, and making concerted efforts to expand and diversify its participants. The team has made inclusive changes to the questionnaire; instead of asking for participants’ sex and gender, they ask if they have an intact uterus.
“Our studies inform the broader body of literature on fertility and enable us to embrace a model of what inclusive reproductive epidemiology should look like,” Wesselink says.
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