Starting pregnancy at a healthy weight and gaining the right amount during pregnancy is critical to giving a baby a healthy start in life, the March of Dimes said today in response to new guidelines from the Institute of Medicine (IOM).

The Institute of Medicine issued new guidelines for the amount of weight a woman should gain during pregnancy. While the guidelines for underweight, normal weight and overweight women were unchanged, the IOM added a new category for obese women, with a narrow range of weight gain. Those women should only gain between 11 and 20 pounds during pregnancy.

We have a serious concern about obesity and the complications it can cause during pregnancy and delivery for the woman and her baby, said Alan Fleischman, M.D., medical director of the March of Dimes. We realize that this is a sensitive subject for many women and that some health care professionals are uncomfortable discussing it, but weight is a risk factor that can be modified. If a woman starts pregnancy at a healthy weight, it can lower the risk of a preterm birth, birth defects, and other complications, including a c-section.

Since the mid-1990s, about half of women of childbearing age are overweight, according to the IOM report.

Gaining too much, or not enough weight during pregnancy can affect the health of a newborn. Women who are overweight or obese during pregnancy are at greater risk for several complications including:

-- Infertility
-- Labor and delivery complications, including c-sections
-- Hypertension, gestational diabetes, preeclampsia
-- Delivery of large-for-gestational-age infants

Women who are underweight also have a greater risk of having a premature or low birthweight baby.

Babies born to overweight and obese mothers may face their own challenges. These newborns are at increased risk of:

-- Being born prematurely
-- Fetal and neonatal death
-- Having certain birth defects, especially neural tube defects
-- Needing special care in a neonatal intensive care unit (NICU)

-- Being obese in childhood

Preterm birth is a serious health problem that costs the United States more than $26 billion annually, according to the IOM. It is the leading cause of newborn death and babies who survive an early birth often face the risk of lifetime health challenges, such as breathing problems, mental retardation and others. Even babies born just a few weeks too soon (34-36 weeks gestation, also known as late preterm birth) have higher rates of death and disability than full-term babies.

The new IOM report also added rates for the amount of weight a woman should gain in the second and third trimesters of pregnancy -- a pound a week for underweight and normal weight women and about a half-pound for overweight and obese women.

The March of Dimes, along with other national organizations concerned with maternal and infant health, co-sponsored the IOM study.

Medicine