Researchers studied 300 children whose mothers took fish oil and/or probiotics during pregnancy and after birth. They found that babies whose mothers took fish oil had different levels of healthy fats in their blood at 6 months old, particularly more omega-3 fatty acids and better cholesterol profiles. These changes were most noticeable at 6 months and became less clear as children got older. The study suggests that what pregnant mothers take can influence their baby’s developing body chemistry, though the long-term importance of these changes isn’t yet fully understood.

The Quick Take

  • What they studied: Whether fish oil and probiotic supplements taken by pregnant women affect the blood chemistry of their babies and young children
  • Who participated: 300 children whose mothers participated in a study during pregnancy and the first 6 months after birth. The mothers were randomly assigned to take fish oil, probiotics, both, or neither (placebo).
  • Key finding: Babies whose mothers took fish oil had higher levels of omega-3 fatty acids and healthier cholesterol patterns in their blood at 6 months old. These differences were most noticeable at 6 months and less clear as children got older.
  • What it means for you: This research suggests that maternal fish oil supplementation during pregnancy may influence a baby’s developing metabolism. However, it’s unclear whether these blood chemistry changes lead to better health outcomes long-term. Talk to your doctor before taking supplements during pregnancy.

The Research Details

This was a randomized controlled trial, which is considered one of the strongest types of research studies. Pregnant women were randomly divided into four groups: one group took fish oil, another took probiotics, a third took both supplements, and a fourth took placebo (fake pills). The mothers took their assigned supplements from early pregnancy through 6 months after giving birth. Researchers then measured the blood chemistry of the children at 6 months old and again at 1, 2, and 5-6 years of age using a special technique called metabolomics, which identifies hundreds of different substances in the blood.

The researchers used advanced statistical methods to compare the blood chemistry between the four groups at each age. They looked at whether the overall pattern of blood chemicals was different between groups, and then examined specific chemicals one by one. They also tracked how these chemicals changed over time as children grew.

This research design is important because it helps determine whether the supplements actually caused the changes in blood chemistry, rather than other factors. By randomly assigning mothers to different groups, researchers can be more confident that differences between groups are due to the supplements themselves. Measuring blood chemistry over several years helps show whether early changes persist or fade as children grow.

This study has several strengths: it included 300 children (a reasonably large sample), used random assignment to reduce bias, and followed children over multiple years. The researchers used sophisticated laboratory methods to measure blood chemicals accurately. However, the study only measured blood chemistry and didn’t track whether these changes led to actual health differences. Some of the findings at older ages were not statistically significant after accounting for multiple comparisons, suggesting they may have occurred by chance.

What the Results Show

At 6 months of age, babies whose mothers took fish oil showed clear differences in their blood chemistry compared to babies whose mothers took placebo. Specifically, these babies had higher levels of omega-3 fatty acids (healthy fats found in fish) and a better ratio of omega-3 to omega-6 fatty acids. They also had higher levels of certain cholesterol particles called high-density lipoproteins, which are considered protective for heart health.

Interestingly, babies whose mothers took only probiotics (without fish oil) did not show these same changes in blood chemistry at 6 months. This suggests that the fish oil, not the probiotics, was responsible for the differences observed.

As children grew older (at 1, 2, and 5-6 years of age), the differences in blood chemistry between groups became much less noticeable. While researchers found 24 metabolites (different blood chemicals) that appeared different between groups at these older ages, these differences were not statistically significant after accounting for the possibility of finding differences by chance.

The study found that fish oil’s effects on blood chemistry were strongest when combined with probiotics, though the addition of probiotics didn’t add major new benefits beyond what fish oil alone provided. The changes in blood chemistry were most pronounced at 6 months and gradually became less distinct as children aged, suggesting that the early effects of maternal supplementation may diminish over time.

Previous research has shown that fish oil supplements can increase omega-3 fatty acids in blood. This study extends that knowledge by showing that when pregnant women take fish oil, their babies are born with higher omega-3 levels, suggesting the nutrients cross from mother to baby during pregnancy and breastfeeding. However, most prior studies looked at direct supplementation of children, not maternal supplementation during pregnancy. This research fills an important gap by examining how maternal nutrition influences infant metabolism.

The study only measured blood chemistry and didn’t track whether these changes led to better health outcomes for the children. It’s unclear whether having higher omega-3 fatty acids at 6 months actually benefits children’s development or long-term health. The effects observed at older ages were weak and not statistically significant, making it hard to know if they’re real or due to chance. The study didn’t measure how much fish oil or probiotics actually made it into breast milk, so we don’t know the exact amount babies received. Additionally, the study population may not represent all ethnic groups or socioeconomic backgrounds equally.

The Bottom Line

Based on this research alone, we cannot recommend that all pregnant women take fish oil supplements. While the study shows fish oil can increase omega-3 fatty acids in babies’ blood, we don’t yet know if this leads to better health. Pregnant women interested in fish oil supplementation should discuss it with their healthcare provider, as some fish oil supplements may contain mercury or other contaminants. The American College of Obstetricians and Gynecologists recommends that pregnant women eat 8-12 ounces of low-mercury fish per week as a safer way to get omega-3 fatty acids.

This research is most relevant to pregnant women considering supplements and healthcare providers advising them. Parents of young children may find it interesting but shouldn’t change their child’s diet based on this study alone. People with heart disease or high cholesterol might be interested in the findings about cholesterol particles, but should consult their doctor before making changes. This research is less relevant to people who aren’t pregnant or planning pregnancy.

The most noticeable changes in blood chemistry appeared at 6 months of age. By 1-2 years old, the differences between groups were much smaller. By 5-6 years old, the effects were minimal. This suggests that any benefits from maternal fish oil supplementation would be most relevant during infancy, though we don’t yet know if these blood chemistry changes translate to actual health benefits.

Want to Apply This Research?

  • If pregnant or planning pregnancy, track daily fish and omega-3 intake (servings of fatty fish, fish oil supplements, or plant-based omega-3 sources) and discuss supplementation plans with your healthcare provider. Record any supplements taken and dates to share with your doctor.
  • Rather than waiting for supplement recommendations, pregnant women can increase omega-3 intake through food by eating 2-3 servings per week of low-mercury fish like salmon, sardines, or trout. This provides similar benefits to supplements with lower contamination risk. Log fish meals in the app to track omega-3 intake.
  • If taking supplements during pregnancy, use the app to track supplement adherence and any side effects. After birth, if breastfeeding, continue tracking omega-3 intake since these nutrients pass into breast milk. For children, track fish consumption as part of overall diet quality, though this study doesn’t provide specific recommendations for children’s supplementation.

This research describes changes in blood chemistry but does not prove that these changes improve health outcomes. Pregnant women should not start, stop, or change any supplements without consulting their healthcare provider first. Fish oil supplements may interact with medications or increase bleeding risk in some people. Some fish oil products may contain mercury or other contaminants. This article is for educational purposes and should not replace medical advice from a qualified healthcare professional. Always discuss supplementation plans with your doctor before pregnancy or during pregnancy.