Historical studies on children born during times of famine show they have twice the risk as the general population of developing schizophrenia and other mental illnesses involving psychotic episodes. Recent research done in Sweden found that extremely inadequate weight gain carries the same elevated risk even in well-fed populations. Other risks include babies who are born premature or underweight.
So just how much weight gain in pregnancy is "just right"? Current recommendations are based on a woman's pre-pregnancy weight and tend to be higher for women at a lower body mass index (or BMI), an indicator of body fat. The Institute of Medicine recommends that underweight women gain between 27 and 40 pounds and that overweight women only gain between 15 and 25 pounds during pregnancy. Keeping weight gain in these suggested ranges should also help limit the amount of "baby weight" a woman will need to lose after delivery to get back to a healthy weight.
Work with your doctor on the right amount for you to gain and the best food sources to ensure a healthy diet that benefits you and your baby. Keep in mind that mom's weight gain alone isn't a strong indicator of the baby's general growth and well-being. Ultrasounds and other testing will provide a more complete picture as the pregnancy progresses.