New research reveals many prenatal vitamins don't contain enough of the nutrients that are essential for a healthy pregnancy, while others contain harmful levels of toxic metals. The study checked the amounts of choline and iodine in nonprescription and prescription prenatal vitamins. The research also checked for toxic metals like arsenic, lead and cadmium. The researchers tested a sample of 47 different prenatal vitamins (32 nonprescription and 15 prescription products) bought from online and local stores where people commonly shop. They then measured the actual amounts of choline and iodine in their lab versus what was on the label and also checked for arsenic, lead and cadmium. They compared their findings with official safety standards within 20% of the claimed amount.