Not only do prenatal vitamins benefit your beauty, but new research shows that they’re vital to preventing autism, too.In fact, the link is so conclusive that we recommend any woman in the potentially pregnant age range—from 12 to 50 years of age who isn’t absolutely celibate—to take prenatal vitamins containing DHA.Researchers have found that prenatal vitamins decrease a child’s risk of autism and autism spectrum disorders by forty percent! The data are from a substantial set of studies headed up by a group at the University of California at Davis—the CHARGE group (Childhood Autism Risks from Genetics and Environment). A second study has come out finding these results. Two studies with the same results is four times as meaningful as one, so this is news we need to take to heart.They’re trying to uncover the cause of the increase in autism and autism spectrum disorders in America and so far have come up with some important findings, like this: Farmers who spray their crops with pesticides and use their own well water for household drinking have a substantially greater risk of having children with birth defects than those using “city water” as their drinking source.MORE: How Much Water Do You Really Need?But this finding is even more actionable. In this study in July’s Epidemiology (22: 476-485), they found a strong association between children who developed autism and the lack of prenatal vitamin use by their mothers for the three months before pregnancy and the first month of pregnancy. This information is so important because many women who are not planning to become pregnant don’t start taking prenatal vitamins until they realize they’re pregnant—which usually happens after that vital first month.As if the health implications were not enough, prenatal vitamins also stock some major beauty benefits!QUIZ: What’s Your Eating Personality?Folic acid (the synthetic form of the B vitamin “folate”) adds about 400 to 800 micrograms to your diet, which reduces the incidence of birth defects. This is important because we don’t always absorb all the folate in our food. Plus, B vitamins like folate aid cell turnover, one reason you may notice you skin’s healthy glow during pregnancy.Taking a prenatal vitamin that contains the key omega-3 fatty acid, DHA, helps meet the goal of 600 mg a day. This aids your child’s brain development. And they offer major health and beauty benefits to you, too. A study recently published in the journal Nutrition found that over 25 percent of cardiologists, dermatologists and orthopedists themselves take an omega-3 fatty acid supplement. The added skin benefit is something to smile about. These fatty acids are vital to maintaining healthy skin structure, and can help combat sun damage and dry skin. Omega-3s may protect against depression and boost your mood—and a smile is a proven way to up your attraction factor!MORE: Take Fish Oil to Fight AgingWhen it comes to beauty benefits of vitamins, yes, Biotin can make your hair healthier. An even more likely effect of this B complex vitamin? Stronger, longer nails.WATCH VIDEO: DHA During PregnancySo say yes to prenatal vitamins until age 50 (guys, too, although a multivitamin without iron is recommended; add DHA!). Then switch to an over-50 brand as an insurance policy against an imperfect diet.Want the full lowdown on the best supplements for your beauty? Read our expert supplement guide.And for more great advice from Dr. Oz and Dr. Roizen, read all of their Beauty Equals Health columns.