Couples trying to conceive may need to take a closer look at their diets. A new study shows that high consumption of ultra-processed foods could increase the time it takes to achieve pregnancy for men and influence the size and development of embryos in women.
"Even though ultra-processed foods are so common in our diets, very little is known about their potential relationship with fertility outcomes and early human development," said lead researcher Dr Romy Gaillard, a paediatrician and associate professor of developmental epidemiology at Erasmus University Medical Center, Rotterdam, The Netherlands.

Until now, no research had examined the combined impact of both parents’ consumption of UPFs on the time it takes to conceive and early embryonic growth. The study, published in Human Reproduction, investigated 831 women and 651 male partners enrolled in the Generation R Study Next Programme, a population-based, prospective study tracking parents from pre-conception through childhood.

How the study was conducted

Participants were included during the pre-conception period or during pregnancy between 2017 and 2021. Data on diet and time to pregnancy were collected using detailed questionnaires.

Researchers assessed fecundability, or the chance of conceiving within a month, and subfertility, defined as taking 12 months or more to conceive or requiring assisted reproductive technology.

Early embryonic development was measured via transvaginal ultrasound at seven, nine, and 11 weeks of gestation. The measurements focused on the distance between the embryo’s head and buttocks, as well as the volume of the yolk sac, which is crucial for early embryo growth.

Key findings

The study found that ultra-processed foods made up approximately 22 percent and 25 percent of total food intake for women and men, respectively.

Celine Lin, a PhD student and first author of the study, said, "We observed that UPF consumption in women was not consistently linked to subfertility or time to pregnancy, but was associated with slightly smaller embryonic growth and yolk sac size by the seventh week of pregnancy."

Although these differences were small, Lin emphasised that they are significant from a research perspective and could have population-level implications. The findings suggest that maternal UPF intake may directly influence the environment in the womb, affecting embryonic development from the very start.

Impact on men’s fertility

The research also found that higher UPF consumption in men was associated with an increased risk of subfertility and longer time to achieve pregnancy. However, male UPF intake did not appear to affect early embryo development.

"This may be explained by the sensitivity of sperm to dietary composition," Lin explained.

"Maternal UPF consumption may influence the womb environment in which the embryo develops, while paternal diet affects fertility outcomes through sperm quality."

Recommendations

Dr Gaillard advised that a diet low in ultra-processed foods is ideal for both partners. "A balanced, minimally processed diet benefits not only your own health but also your chances of conception and the healthy development of your unborn child," she said.

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