What you eat before pregnancy may matter more than previously understood, and not just for women.
A new study suggests that higher intake of ultraprocessed food in both men and women is associated with reduced fertility and subtle differences in early embryo development. The findings add to growing evidence that diet quality may play a role in reproductive health for both partners.
The study, published in Human Reproduction, followed 831 women and 651 male partners from before conception through early pregnancy. Researchers assessed diet using questionnaires and calculated how much of each person’s intake came from ultraprocessed foods, then examined time to pregnancy and early embryo development using ultrasound measurements taken at seven, nine and 11 weeks.
Researchers found that higher ultraprocessed food intake in men was associated with a longer time to conception and a higher likelihood of subfertility, defined as taking 12 months or longer to conceive or requiring fertility treatment. In women, higher intake was not consistently linked to time to pregnancy but was associated with slightly smaller embryo size and yolk sac volume early in pregnancy. The yolk sac plays an important role in early development.
“We observed that UPFs consumption in women was not consistently related to the risk of subfertility and time to pregnancy, but was associated with slightly smaller embryonic growth and yolk sac size by the seventh week of pregnancy.”
These differences were small, but the researchers note they may still matter at a population level.
Ultraprocessed foods include items that are industrially formulated and often higher in added sugars, salt, fats and additives while being lower in fiber and whole food ingredients. In some countries, these foods make up a large share of daily intake.
The findings also highlight a broader point about fertility: both partners’ health matters.
“Our findings suggest that a diet low in UPFs would be best for both partners, not only for their own health, but also for their chances of pregnancy and the health of their unborn child.”
The researchers emphasize that the study shows associations, not cause and effect. Diet was measured using a single questionnaire, and the study population may not reflect all groups.
“Importantly, as this is an observational study, our study shows associations, but cannot prove direct causal effects of UPF consumption on these early life outcomes.”
For readers, the takeaway is less about eliminating specific foods and more about overall patterns. Diets higher in ultraprocessed foods tend to be lower in nutrients that support overall health. The study also reinforces a shift in how fertility is understood, moving beyond a focus on maternal health alone to include the role of both partners before conception.
This study was published in Human Reproduction. The authors reported no conflicts of interest.