Researchers studied over 17,000 Danish women to see how their diet during pregnancy affected their children’s growth and weight up to age 18. They found that women who ate a high-protein, low-sugar diet during pregnancy had children who weighed about 5.7 pounds more and had a higher body mass index (BMI) at age 18 compared to children whose mothers ate a more moderate diet. This suggests that the food choices pregnant women make might influence their children’s weight and health for many years after birth.

The Quick Take

  • What they studied: Whether eating a high-protein, low-sugar diet during pregnancy affects how much children weigh as they grow up
  • Who participated: 17,551 pregnant women from Denmark and their children, followed from birth until age 18
  • Key finding: Children whose mothers ate high-protein, low-sugar diets weighed about 5.7 pounds more and had higher BMI measurements at age 18 compared to children whose mothers ate moderate amounts of protein and sugar
  • What it means for you: If you’re pregnant or planning to become pregnant, this research suggests that very high-protein, low-sugar diets might not be the best choice for your baby’s long-term weight. However, this is one study, and you should talk with your doctor about the best diet for your individual situation.

The Research Details

This study used information collected from thousands of Danish women and their children over many years. Researchers looked back at what the women ate during pregnancy and then tracked how much their children weighed at different ages—from birth all the way to 18 years old. They divided the women into groups based on how much protein they ate and how much sugar was in their diet (called glycemic index). The researchers then compared the children’s weights and growth between these different groups.

To make sure they were comparing similar groups of people, the researchers adjusted their analysis to account for other factors that might affect a child’s weight, like the mother’s starting weight, how much weight she gained during pregnancy, and family background. This helps make sure any differences they found were actually related to diet and not other factors.

This type of study is important because it follows real people over a long time period, which helps researchers understand how pregnancy diet affects children’s health years later. Rather than just looking at one moment in time, this study tracked children for 18 years, giving a much clearer picture of long-term effects.

This study has several strengths: it included a large number of women (over 17,000), followed children for a long time (18 years), and used careful statistical methods to account for other factors. However, because it’s an observational study (watching what people naturally eat rather than assigning them to specific diets), we can’t be completely certain that the diet caused the weight differences—other unmeasured factors could be involved. The women who chose high-protein diets may have differed in other ways we don’t know about.

What the Results Show

The main finding was that children born to mothers who ate high-protein, low-sugar diets during pregnancy weighed about 2.59 kg (5.7 pounds) more at age 18 and had a BMI that was 0.72 kg/m² higher compared to children whose mothers ate moderate amounts of protein and sugar. This difference was consistent across the 18-year follow-up period.

Interestingly, the mothers who ate high-protein, low-sugar diets started out slightly heavier before pregnancy (about 3.7 pounds heavier) and had a slightly higher BMI before becoming pregnant. However, they gained about the same amount of weight during pregnancy as the other women, so the difference in their children’s weight wasn’t explained by how much weight the mothers gained while pregnant.

The researchers found these patterns held true even after accounting for many other factors that could affect a child’s weight, including the mother’s age, education level, smoking status, and whether she had diabetes or high blood pressure.

The study looked at children’s weight and BMI at multiple time points throughout their lives—at birth, at various ages during childhood, and at age 18. The pattern of higher weight in the high-protein, low-sugar diet group appeared consistently across these different ages, suggesting this is a lasting effect rather than something temporary.

Previous research has shown that what pregnant women eat can affect their babies’ development and future health. Some studies suggested that high-protein diets might be beneficial during pregnancy, while others raised concerns about very high protein intake. This study adds important information by showing that very high-protein, low-sugar diets during pregnancy may be associated with children who are heavier later in life, which is different from what some earlier research suggested might happen.

This study has important limitations to consider. First, it’s observational, meaning researchers watched what women naturally ate rather than assigning them to specific diets. This means we can’t be completely sure the diet caused the weight differences—other factors we didn’t measure could be responsible. Second, the study only included Danish women, so results might be different in other populations. Third, the researchers estimated what women ate based on questionnaires, which might not be perfectly accurate. Finally, the women who chose high-protein diets may have been different in other ways (like exercise habits or other lifestyle factors) that weren’t fully accounted for in the analysis.

The Bottom Line

Based on this research, pregnant women should be cautious about following very high-protein, low-sugar diets during pregnancy. Instead, a balanced diet with moderate amounts of protein and a mix of healthy carbohydrates appears to be a safer choice. This is a moderate-confidence recommendation based on one observational study. Pregnant women should discuss their diet with their healthcare provider to find the best approach for their individual situation.

This research is most relevant for pregnant women and those planning to become pregnant. It’s also important for healthcare providers who advise pregnant women about nutrition. If you’re not pregnant, this study doesn’t directly apply to you, though it does highlight how important maternal nutrition is for children’s long-term health.

The effects of maternal diet during pregnancy appear to last for many years—this study followed children until age 18 and found consistent differences throughout their lives. This suggests that dietary choices during pregnancy may have lifelong implications for a child’s weight and health.

Want to Apply This Research?

  • If pregnant, track daily protein intake (grams) and monitor the glycemic index of carbohydrates eaten, aiming for a balanced approach rather than extreme high-protein intake. Log meals weekly and note any patterns.
  • Shift from high-protein focused meals to balanced meals that include moderate protein (about 25-30% of calories), healthy carbohydrates like whole grains and vegetables (45-50%), and healthy fats (20-25%). Use the app to swap high-protein snacks for balanced alternatives.
  • For pregnant users: track protein and carbohydrate balance weekly and discuss patterns with healthcare provider at prenatal visits. For postpartum tracking: monitor child’s growth measurements at regular checkups and compare to growth charts, noting any concerning patterns to discuss with pediatrician.

This research is observational and shows an association, not definitive proof of cause and effect. Pregnant women should not make major dietary changes based solely on this study. All dietary decisions during pregnancy should be made in consultation with a healthcare provider, such as an obstetrician, midwife, or registered dietitian, who can consider individual health circumstances, medical history, and nutritional needs. This information is for educational purposes only and should not replace professional medical advice.