Gram Research analysis of a 2026 cross-sectional study of 111 pregnant women found that those eating home-grown rice had higher blood mercury levels than store-bought rice consumers, and babies whose mothers had elevated mercury exposure weighed less at birth and had smaller head measurements. The mercury appeared to affect fetal growth through changes in placental gene regulation. However, overall mercury levels were relatively low, and because the study captured only one moment in time, researchers cannot definitively prove mercury caused the smaller babies.
Researchers studied 111 pregnant women and their babies to see if mercury from rice could affect how babies grow in the womb. They found that women who ate home-grown rice had higher mercury levels in their blood than those who bought rice from stores. Babies whose mothers had higher mercury exposure tended to weigh less at birth and had smaller head measurements. The study suggests mercury from rice might affect baby development, but because it only looked at one point in time rather than following women over months, more research is needed to prove this connection.
Key Statistics
A 2026 cross-sectional study of 111 mother-infant pairs found that pregnant women consuming home-grown rice exhibited significantly higher mercury concentrations in their blood compared to those consuming market-purchased rice.
According to research reviewed by Gram, prenatal mercury exposure showed a nonlinear relationship with birth weight Z-score and biparietal diameter Z-score, suggesting that fetal growth effects vary across different mercury exposure levels.
The 2026 study identified associations between maternal mercury levels and altered placental 5-methylcytosine levels, indicating that mercury may affect fetal development through changes in how genes are regulated.
Cord blood mercury concentrations in the 111 study participants demonstrated a curved relationship with birth weight rather than a simple linear association, suggesting threshold or dose-dependent effects on fetal growth.
The Quick Take
- What they studied: Whether mercury found in rice, especially home-grown rice, could affect how well babies grow before birth
- Who participated: 111 pairs of pregnant women and their newborn babies from a population where rice is a major food source
- Key finding: Babies whose mothers had higher mercury levels in their blood tended to weigh less at birth and have smaller head sizes, with home-grown rice eaters showing higher mercury levels than store-bought rice consumers
- What it means for you: If you’re pregnant and live in an area where home-grown rice is common, you may want to consider eating store-bought rice instead, though overall mercury levels in this study were low. Talk to your doctor about your specific situation before making changes
The Research Details
Researchers collected blood samples from 111 pregnant women at one point in time and also tested samples from the placenta (the organ that feeds the baby) and umbilical cord blood after birth. They measured how much mercury was in each sample and compared these levels to how much the babies weighed and how big their heads were at birth. The team also looked at whether mercury affected certain chemical markers in the placenta that control how genes work. They adjusted their analysis to account for other factors that might affect baby size, like the mother’s age and whether she smoked.
This research approach helps identify whether a connection exists between mercury exposure and baby growth. By measuring mercury in multiple places (mother’s blood, placenta, and cord blood), researchers could see how mercury moves from mother to baby. However, because this was a snapshot in time rather than following women throughout pregnancy, it can only show associations, not prove that mercury definitely causes smaller babies.
The study measured mercury in multiple samples, which strengthens the findings. However, the cross-sectional design (taking measurements at one time point) is a limitation because it cannot prove cause and effect. The sample size of 111 pairs is moderate. The researchers were careful to adjust for other factors that might influence results. The authors themselves note that findings should be interpreted cautiously and not generalized to all populations
What the Results Show
Pregnant women who ate home-grown rice had higher mercury levels in their blood compared to those who bought rice from markets. When researchers looked at the relationship between mercury levels and baby size, they found that higher maternal mercury exposure was linked to lower birth weights and smaller head measurements in newborns. The relationship was not simply linear (where more mercury always means smaller babies), but rather showed a curved pattern, suggesting that the effect might be stronger at certain mercury levels. Cord blood mercury levels also showed this curved relationship with birth weight.
The study found that mercury levels in the placenta were associated with changes in a chemical marker called 5-methylcytosine, which controls how genes are expressed. This suggests that mercury might affect baby development through changes in how genes work, not just by direct toxic effects. Overall, mercury levels in this population were relatively low compared to other studies, which means the effects observed were subtle rather than dramatic.
Previous research has shown that mercury exposure during pregnancy can harm fetal development, but most studies focused on fish consumption or occupational exposure. This study adds to that knowledge by identifying rice, particularly home-grown rice, as a potential dietary source of mercury. The finding that home-grown rice contains more mercury than store-bought rice is important because it suggests that farming practices or soil conditions may affect mercury levels in food.
This study only looked at one moment in time, so it cannot prove that mercury caused the smaller babies. The sample size, while reasonable, was not huge. The study was done in a specific population where rice is a major food source, so results may not apply to other groups. The researchers could not determine exactly how much rice each woman ate, only whether she typically ate home-grown or store-bought rice. The study did not follow women throughout their entire pregnancy, so researchers could not track how mercury levels changed over time
The Bottom Line
If you are pregnant or planning to become pregnant and live in an area where home-grown rice is common, consider eating store-bought rice instead, as it appears to have lower mercury levels. This recommendation is based on moderate evidence from this one study. Discuss your specific dietary choices with your healthcare provider, especially if you eat large amounts of rice. For the general population in areas where rice is not a major staple, this finding is less directly applicable
Pregnant women and women planning to become pregnant in regions where home-grown rice is a dietary staple should pay attention to this research. Healthcare providers working with these populations should be aware of rice as a potential mercury source. The findings are less relevant for people in Western countries where rice consumption is lower and store-bought rice is the norm
If a pregnant woman switched from home-grown to store-bought rice, mercury levels in her blood would likely decrease gradually over weeks to months. The effects on fetal growth would theoretically be most important during the second and third trimesters when the baby is growing most rapidly. Any benefits from reducing mercury exposure would likely be seen in birth weight and head size measurements at delivery
Frequently Asked Questions
Can eating rice during pregnancy harm my baby?
Rice itself is safe, but home-grown rice may contain higher mercury levels than store-bought rice. A 2026 study of 111 pregnant women found that those eating home-grown rice had higher mercury exposure linked to slightly smaller babies at birth. Switching to store-bought rice may reduce this risk.
How much mercury from rice is dangerous during pregnancy?
The study found that overall mercury levels in this population were relatively low, yet still showed associations with reduced birth weight and head size. There is no established safe threshold identified in this research, so minimizing exposure by choosing store-bought over home-grown rice appears prudent if you live in affected regions.
Should I stop eating rice if I’m pregnant?
No, you don’t need to stop eating rice. Instead, if you have access to home-grown rice, consider switching to store-bought rice, which the study found contained lower mercury levels. Rice remains a nutritious food; the concern is specifically about mercury contamination in home-grown varieties.
Does this study apply to all pregnant women everywhere?
This study was conducted in a population where rice is a major dietary staple and home-grown rice is common. The findings may not apply to regions where store-bought rice is standard or where rice consumption is lower. Discuss your specific situation with your healthcare provider.
How does mercury get into rice plants?
The study did not investigate how mercury enters rice, but it found that home-grown rice had higher levels than store-bought varieties. This suggests soil conditions, farming practices, or water sources may differ between home gardens and commercial farms, affecting mercury accumulation in the plants.
Want to Apply This Research?
- Track weekly rice consumption by type (home-grown vs. store-bought) and source, noting any changes in dietary patterns during pregnancy
- If pregnant, log rice meals with source information and set a goal to transition from home-grown to store-bought rice if currently consuming home-grown varieties
- Monitor mercury exposure sources over the course of pregnancy by tracking rice consumption patterns monthly and correlating with prenatal health markers discussed with your healthcare provider
This research is a cross-sectional study that identifies associations but cannot prove cause and effect. The findings apply primarily to populations where home-grown rice is common and should not be generalized to all populations. Pregnant women should consult with their healthcare provider before making dietary changes based on this research. This article is for educational purposes and should not replace professional medical advice. If you have concerns about mercury exposure during pregnancy, speak with your obstetrician or midwife.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.