A 2026 meta-analysis of 25 studies involving 26,019 birth defect cases found that not taking folic acid supplements regularly increased neural tube defect risk by 134%, while regular prenatal checkups reduced overall birth defect risk by 55-64%. Maternal age over 35 and obesity also significantly increased risk, but getting proper healthcare screening and supplementation are the most controllable prevention strategies.
Researchers in China analyzed 25 studies involving over 26,000 cases of birth defects to identify what factors increase a baby’s risk of being born with health problems. According to Gram Research analysis, the biggest preventable risk factor was not taking folic acid supplements before and during pregnancy—especially for neural tube defects like spina bifida. The study also found that mothers over 35, those with obesity, and those who didn’t get regular prenatal checkups faced higher risks. Good news: getting premarital exams and regular pregnancy checkups reduced birth defect risk by more than half.
Key Statistics
A 2026 meta-analysis of 25 Chinese studies involving 26,019 birth defect cases found that irregular folic acid supplementation increased neural tube defect risk by 134% compared to regular supplementation.
According to the same 2026 meta-analysis, getting regular prenatal examinations reduced birth defect risk by 59%, and premarital examinations reduced risk by 64%.
The 2026 meta-analysis found that maternal obesity (BMI over 30) increased birth defect risk by 42%, and maternal age 35 and older increased risk by 26%.
The study identified that exposure to harmful substances during pregnancy increased birth defect risk by 45%, and using contraceptives within 6 months before pregnancy increased risk by 36%.
The Quick Take
- What they studied: What things make it more or less likely for a baby to be born with birth defects in China between 2019 and 2025?
- Who participated: The analysis combined data from 25 different research studies that together looked at 26,019 babies born with birth defects in China. The studies examined mothers of different ages, weights, and economic backgrounds.
- Key finding: Not taking folic acid supplements regularly increased the risk of neural tube defects (problems with the brain and spine) by 134%. Getting regular prenatal checkups cut the risk of birth defects in half or more.
- What it means for you: If you’re planning to get pregnant or are pregnant, taking folic acid supplements and getting regular medical checkups are two of the most important things you can do to protect your baby’s health. This is especially important if you’re over 35 or have obesity.
The Research Details
Researchers searched nine different medical databases for studies published between January 2019 and December 2025 about what causes birth defects in China. They found 25 high-quality studies that together included information about 26,019 babies born with birth defects. Two researchers independently reviewed each study to make sure the information was accurate and reliable.
They used a special statistical method called meta-analysis to combine all the data from these 25 studies. This allowed them to look at patterns across thousands of cases instead of just one study. When studies showed very different results from each other, they broke the data down by type of birth defect, region, or study quality to understand why.
The researchers followed strict international guidelines (PRISMA 2020) to make sure their analysis was done properly and could be trusted by doctors and health officials.
By combining 25 studies instead of looking at just one, researchers can see the bigger picture of what really causes birth defects. This approach is much more reliable than a single study because it shows patterns that appear across many different hospitals and regions in China. When doctors and government health officials have this kind of strong evidence, they can make better decisions about how to prevent birth defects.
This is a high-quality meta-analysis that followed international standards for combining research studies. The researchers had two people independently review each study to reduce mistakes. They looked at 25 different studies with over 26,000 cases, which is a large amount of data. However, the studies came from China only, so the results may not apply exactly the same way in other countries. Some of the findings had high variability between studies, which the researchers addressed by breaking down the data by type of birth defect.
What the Results Show
The study identified 17 different factors that influence whether a baby is born with birth defects. The most important preventable factor was irregular folic acid supplementation. When mothers didn’t take folic acid regularly, their risk of having a baby with neural tube defects (like spina bifida) increased by 134%. This was the strongest and most consistent finding across all the studies.
Maternal age and weight also mattered significantly. Mothers aged 35 and older had a 26% higher risk of birth defects. Mothers with obesity (BMI over 30) had a 42% higher risk. These are important because they’re factors women can be aware of when planning pregnancy.
The good news came from healthcare services. Getting premarital examinations reduced birth defect risk by 64%. Regular pregnancy checkups reduced risk by 59%. Birth examinations (ultrasounds and other tests during pregnancy) reduced risk by 55%. These protective effects were consistent and strong across all studies.
Other risk factors included exposure to harmful substances (45% increased risk), using contraceptives within 6 months before pregnancy (36% increased risk), and lower family income below 5,000 yuan (41% increased risk, though this was less certain).
Several other factors showed smaller but still meaningful effects. Having a fever during early pregnancy increased risk by 19%, though this finding was less certain. Taking medications in early pregnancy increased risk by 17%, but again with less certainty. Preterm birth (babies born too early) increased overall birth defect risk by 7%, but for congenital heart disease specifically, the risk jumped to 82% higher. Being small for gestational age increased risk by 38%, though this finding was less certain. Family history of genetic disorders increased risk by 10%, but this was also less certain.
This research confirms what doctors have known for decades: folic acid supplementation is crucial for preventing birth defects, especially neural tube defects. The finding that prenatal care reduces birth defects aligns with global health evidence. However, this study is unique because it specifically examined Chinese populations and identified regional differences in how these factors affect birth defect rates. The research also highlights that some factors (like contraceptive use before pregnancy) may be more relevant in specific cultural or healthcare contexts.
This study only looked at research from China, so the results may not apply exactly the same way in other countries with different healthcare systems or populations. Some of the studies included were smaller or lower quality than others, which could affect the overall results. For some factors, the studies showed very different results from each other, making it harder to know the true effect. The research is based on studies published through 2025, so very recent discoveries aren’t included. Finally, because these are observational studies (not experiments where researchers control what happens), we can’t always be 100% sure that one factor directly causes birth defects—there might be other explanations.
The Bottom Line
Strong evidence: Take folic acid supplements (400-800 micrograms daily) before trying to get pregnant and continue through pregnancy. Get regular prenatal checkups starting as early as possible. Avoid exposure to harmful substances, medications (unless prescribed by your doctor), and harmful chemicals during pregnancy. Moderate evidence: Be aware that being over 35 or having obesity increases risk, and discuss this with your doctor when planning pregnancy. Avoid using contraceptives right up until you want to get pregnant—stop them at least 6 months before trying. Weak evidence: Maintain good mental health and manage stress during pregnancy, though the evidence for this specific factor was less clear.
This research is most relevant for women planning to get pregnant, women who are currently pregnant, and healthcare providers in China and similar healthcare settings. Women over 35, those with obesity, those with lower incomes, and those with family histories of genetic disorders should pay special attention. Healthcare policymakers in China should use this to improve prenatal care access. The findings are less directly applicable to countries with very different healthcare systems or populations, though the folic acid recommendation is universal.
Folic acid supplementation should start at least one month before trying to get pregnant and continue through the first trimester (first 3 months). The protective effects of prenatal care develop gradually—the earlier you start checkups, the better. Most birth defects form in the first 8-12 weeks of pregnancy, so early intervention is critical. You won’t see immediate results, but following these recommendations significantly reduces risk over the course of your pregnancy.
Frequently Asked Questions
What is the most important thing I can do to prevent birth defects?
Taking folic acid supplements regularly is the single most important preventable factor. A 2026 meta-analysis found that irregular folic acid supplementation increased neural tube defect risk by 134%. Start taking 400-800 micrograms daily at least one month before trying to get pregnant and continue through the first trimester.
Does prenatal care really reduce birth defect risk?
Yes, significantly. Research shows that regular pregnancy checkups reduce birth defect risk by 59%, and premarital examinations reduce risk by 64%. Getting early and consistent healthcare screening is one of the most effective ways to prevent birth defects and catch problems early.
I’m over 35—does that mean my baby will have birth defects?
Not necessarily. Being 35 or older increases risk by 26%, but most babies born to older mothers are healthy. The key is to be extra careful about folic acid supplementation, prenatal checkups, and avoiding harmful substances. Discuss your specific risk factors with your doctor.
What harmful substances should I avoid during pregnancy?
The research found that exposure to harmful substances increased birth defect risk by 45%. This includes smoking, alcohol, recreational drugs, and certain chemicals. Discuss any medications, supplements, or workplace exposures with your doctor, as some are safe and others aren’t during pregnancy.
When should I start taking folic acid if I want to get pregnant?
Start taking folic acid at least one month before trying to get pregnant and continue through the first trimester (first 3 months). Most birth defects form in the first 8-12 weeks of pregnancy, so early supplementation is critical for protection.
Want to Apply This Research?
- Track daily folic acid supplementation with a simple yes/no checklist. Set a daily reminder at the same time each day. Monitor completion rate weekly—aim for 100% adherence. Log the specific dose taken (400-800 mcg) to ensure adequate intake.
- Set a daily alarm for folic acid intake at breakfast or dinner. Schedule prenatal appointments in the app calendar and set reminders 3 days before each visit. Create a checklist of questions to ask your doctor at each appointment. Track any medications or supplements you’re taking to discuss with your healthcare provider.
- Weekly review of folic acid adherence rate. Monthly tracking of prenatal appointment completion. Quarterly assessment of overall pregnancy health markers. Long-term tracking of any symptoms or concerns to discuss with your doctor. Use the app to maintain a health history that you can share with your healthcare provider at each visit.
This article summarizes research findings and is not a substitute for professional medical advice. If you are pregnant, planning to become pregnant, or have concerns about birth defects, consult with your healthcare provider or obstetrician. The recommendations in this article are based on research from China and may not apply identically in all healthcare settings or populations. Always follow your doctor’s specific guidance for your individual situation, as personal risk factors may require customized recommendations.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.