Ultra-Processed Foods May Reduce Fertility and Pregnancy Chances

A major international research project suggests that highly processed foods can measurably reduce the likelihood of becoming pregnant. Of particular concern is that the effects appear not only in statistics, but also directly in the quality of early embryos – at the very start of new life.

What researchers really mean by ‘ultra-processed’

The research uses the NOVA classification, which groups foods according to the extent of their industrial processing. In this context, ‘ultra-processed’ does not simply mean food that has been cooked or frozen.

Products typically included in this category are:

• Frozen ready meals and instant noodles
• Sugary drinks, including fizzy drinks and energy drinks
• Packaged snacks: crisps, corn snacks, chocolate bars and biscuits
• Restructured meat products, chicken nuggets and breakfast cereals containing numerous additives
• Part-baked rolls and sliced white bread with lengthy ingredient lists

These products commonly contain numerous additives, heavily refined ingredients, high levels of sugar or fat, and undergo extensive industrial processing. At the same time, they generally provide few vitamins, minerals and dietary fibres.

“The study shows: the greater the proportion of ultra-processed foods in everyday diets, the lower the chances of pregnancy.”

Large cohort, clear pattern: fertility measurably declines

The research group led by Celine H. X. Lin and Romy Gaillard analysed data from several thousand women of reproductive age. The participants recorded their food intake in detail over a number of years. Medical information was also available, including data on fertility treatment.

The analysis revealed a clear pattern: women consuming particularly high amounts of highly processed products became pregnant less often than those whose diets were fresher and less processed. The association remained after the researchers accounted for established influencing factors, including:

• Age
• Body mass index (BMI)
• Smoking
• Educational level and social status

This places diet itself in focus as an independent factor. The gradual nature of the effect is especially noteworthy: there is no ‘magic threshold’ beyond which everything suddenly changes. Each additional share of ultra-processed products in the diet further reduces the probability of pregnancy.

The researchers deliberately describe this as a “robust association”. In other words, the data are strong, but they do not by themselves prove a direct cause-and-effect relationship. What is clear, however, is that the direction of the association aligns with many other findings from nutritional and reproductive medicine.

What is already visible in the laboratory: a look at the early embryo stage

One particular strength of the study is that some of the assessed data came from in vitro fertilisation (IVF) cycles. In this setting, specialists can evaluate embryo quality directly in the laboratory, before implantation in the womb.

This is precisely where a worrying signal emerged: on average, patients with high consumption of ultra-processed foods had embryos of lower quality. Assessments included:

• How regularly and consistently the cells divide
• Whether the embryo’s structure and development appear unremarkable
• How likely the embryo appears to be to develop successfully

This finding indicates that the impact may not begin only at implantation or during later stages of pregnancy. It may already affect egg maturation and the very first cell divisions following fertilisation.

“The early embryo stage responds extremely sensitively to the environment in the mother’s body – and that includes her everyday diet directly.”

Possible biological mechanisms: how food reaches the egg cell

The study itself can only point towards potential mechanisms rather than establish them conclusively. However, several possible explanations are plausible and widely discussed in specialist literature.

Chronic inflammation and metabolic stress

Highly processed products often contain large amounts of rapidly available carbohydrates, saturated fats and salt. This combination can promote mild but persistent inflammatory processes in the body. Such inflammation may disrupt the delicate hormonal balance that is essential for ovulation, egg maturation and implantation.

There is also what is known as oxidative stress: an imbalance between harmful oxygen radicals and the body’s own protective systems. Egg cells are particularly sensitive to these pressures. Damage to genetic material or cellular structures may limit their ability to develop.

Missing protective nutrients – too little of what helps

People who eat many ready-made products generally consume less fruit, vegetables, pulses and unprocessed wholegrain foods. This can mean insufficient intake of:

• Vitamins such as folate, vitamin C and vitamin E
• Plant compounds with antioxidant effects
• Dietary fibres that positively influence blood sugar and gut flora
• High-quality fats, such as omega-3 fatty acids

These nutrients are considered important for stable hormonal signalling, good blood flow to the ovaries and egg-cell quality.

Substances from packaging and additives

Another concern relates to so-called endocrine disruptors. These are substances that may interfere with hormonal processes. They can originate, for example, from certain plastics, coatings, plasticisers or some additives.

Ultra-processed products in particular often come into contact with substantial amounts of packaging material, are heated intensely or stored for long periods. Trace amounts of potentially problematic substances can therefore enter the food – and subsequently the bloodstream of people who eat these products regularly.

Fertility as a societal responsibility – not solely a private matter

In many Western countries, ultra-processed foods now supply more than half of daily calories. At the same time, the proportion of couples experiencing difficulties conceiving is increasing. Professional bodies estimate that around one in six couples struggle to become pregnant.

Against this backdrop, the new study takes on political significance. It points to a possible lever affecting millions of people – and one that can genuinely be changed. Genetics and age cannot be altered, but personal shopping and cooking habits can.

Health experts are therefore calling for:

• Clearer labelling of highly processed products
• More practical nutritional advice in gynaecology practices and fertility clinics
• Measures that make fresh foods more affordable and easier to access

For women and couples hoping to have a child, this provides another reason to examine their own diet critically – well before a pregnancy test becomes relevant.

What those affected can do in practice

No one needs to adopt a completely ‘clean’ diet overnight. Even small but consistent changes can substantially reduce overall exposure and improve the supply of important nutrients.

Practical starting points include:

• Replace soft drinks with water, tea or unsweetened fruit spritzers
• Cook at least one meal a day yourself using fresh ingredients
• Swap crisps and biscuits in the snack drawer for nuts, fruit or natural yoghurt
• When shopping, leave products with exceptionally long ingredient lists on the shelf
• Replace ready-made sauces and dressings with simple combinations of oil, vinegar, herbs and spices

The key is not strict avoidance, but shifting the balance. Increasing the proportion of fresh, minimally processed foods noticeably can remove a significant part of the potential risk.

Fertility begins long before trying for a baby

One central point made by the researchers is that egg-cell health does not arise only in the month when a couple starts trying to conceive. It develops over years, shaped by diet, stress, physical activity, environmental factors and hormonal status.

Anyone intending to have children in a few years’ time can begin strengthening the foundation now through simple, lasting dietary habits. This also includes avoiding major weight fluctuations and sharp swings in blood sugar, as both place strain on hormonal balance.

Ultimately, the study does not offer a dogma, but a clear wake-up call: our convenient, industrially driven food system has consequences that may extend beyond blood test results or waistlines. It may interfere with one of the most sensitive functions of the body – the ability to create new life.