Prenatal Vitamins And Autism: Can Supplements During Pregnancy Affect The Odds Of Autism?

Any preconception checklist you might look at when you've just decided you would like to get pregnant will emphasize the importance of prenatal vitamins.

Any pregnant woman should strive to get all the right nutrients both during and just before pregnancy, but some vitamins and minerals are especially essential. Everyone, including folks who don't have kids and don't want them, probably knows that folic acid plays a key role in preventing neural tube defects like spina bifida and anencephaly by now. Pregnant women also need double the amount of iron they take in, along with plenty of calcium and vitamin D to support the growth of healthy bones and teeth in their babies. 

Sure, it's possible to get these nutrients — in the right amounts — through diet alone, but taking a prenatal supplement, starting about a month before you begin trying to conceive, allows future parents to have peace of mind. While it's clear that prenatal supplements should never be used as a substitute for a healthy and balanced diet, no doctor would hesitate to recommend them. 

How prenatal vitamins impact the odds of autism: What does science say?

Several older studies have toyed with the idea that maternal prenatal vitamin intake may influence the odds that a child will end up being on the autism spectrum, but let's look at more recent data. 

A large, four-year, study of 45,300 Israeli children was published in 2018. The study included all kids born between January 1, 2003 and December 31, 2007 with an autism spectrum disorder diagnosis and a random sample of a third of all other kids born during the same time period.

The researchers associated taking prenatal supplements (including folic acid) before pregnancy with a 61 percent lower rate of autism, and taking prenatal supplements during pregnancy with a 73 percent lower chance.

The difference between taking prenatal vitamins and not taking them was statistically significant even after confounding factors were taken into account, but the researchers noted that there may have been confounders they didn't account for. Their sample size wasn't sufficient to come to definite conclusions either, and they didn't have the chance to do a sibling control analysis. 

A study published in 2019 looked at families in which one child was already diagnosed as being on the autism spectrum — families deemed to be "at high risk" of having another autistic child. This study found that 14.1 percent of children whose mothers took prenatal supplements in the first month of pregnancy were later diagnosed as being on the autism spectrum, compared to 32.7 percent of those whose moms did not take prenatal supplements during this time. The overall sample size was very small, however — only 241 younger siblings of autistic children. 

A third study, meanwhile, found that taking fish oil supplements during pregnancy wasn't associated with lower odds that a baby would be on the autism spectrum, but taking folic acid supplements was. This is interesting because, as the authors noted, women taking fish oil tend to have some of the same (health-conscious) characteristics as those taking folic acid. It may, in other words, be something about folic acid itself, rather than other random factors that tend to be present in mothers who take folic acid, that lowers the odds of autism. 

What should this mean for you if you're trying to get pregnant?

In my opinion, absolutely nothing. Pregnant women and those who are trying to conceive are advised to take prenatal supplements that ensure they get the right daily doses of all the most important nutrients for a reason. That reason is to promote healthy fetal development right alongside maternal health (remember, if you don't get enough calcium through your diet, your body will divert your own stores, from your bones, to your baby).

At SteadyHealth, we'd advise anyone who is trying to get pregnant or already expecting to make healthy and balanced eating a priority. Because you'd be surprised how little you actually know about which nutrients you're getting through your daily diet and in which amounts, it may be a good either to:

• Get tested for nutritional deficiencies before you try to get pregnant. 
• Use one of the many handy apps now available to track your diet and to get an honest picture of your nutrition. If using a nutrition-tracking app for a while shows that your diet isn't adequate, meaning you don't get the daily recommended amounts of important vitamins and minerals or macronutients like proteins, fats, or carbs, you can then take steps to adjust your diet before you try to conceive.