By Serena Gordon
HealthDay Reporter Mon Oct 1, 11:45 PM ET

MONDAY, Oct. 1 (HealthDay News) -- While lower cholesterol is
generally considered a good thing, new research suggests that very low
cholesterol levels in pregnant women may harm the health of the fetus.

Expectant mothers whose total cholesterol levels were under 159
milligrams per deciliter (mg/dL) gave birth -- on average -- to babies
weighing about one-third of a pound less than babies born to mothers
whose cholesterol levels exceeded 159 mg/dL, the researchers found.

Additionally, 12.7 percent of white women with low cholesterol levels
gave birth prematurely, compared to just five percent of those with
higher cholesterol levels. No such association was found in black
women, however.

"To our surprise, we found that white women with very low cholesterol
also have a significant risk of having babies born prematurely, " said
Dr. Max Muenke, chief of medical genetics at the U.S. National Human
Genome Research Institute in Bethesda, Md.

Results of the study are in the October issue of Pediatrics.

"At this point, it's not even clear if it's the low cholesterol
itself, or another lipid," he said, adding that more research is
needed to confirm these findings.

"This study intuitively makes some sense," said Dr. Robert Welch,
chair and program director for obstetrics and gynecology at St. John
Health's Providence Hospital in Southfield, Mich. "Cholesterol is a
building block for membranes, hormones and proteins, so it makes sense
that if you have low cholesterol, your baby won't have the substrate
it needs to grow."

Each year, more than half a million babies are born prematurely in the
United States, according to the March of Dimes. Medical advances have
brought down the incidence rates for many diseases and conditions, but
that's not been the case with premature or low birth weight babies.

In 1994, 11 percent of babies were born prematurely, and 7.3 percent
were considered low birth weight. In 2004, those numbers were 12.5
percent and 8.1 percent, respectively. A preterm birth is one that
occurs before 37 weeks, and a baby under five and a half pounds is
considered to have a low birth weight.

According to Muenke, because previous studies have shown that high
cholesterol levels -- over 300 mg/dL -- may lead to premature birth,
the researchers wanted to know if very low levels could also have an
effect.

The researchers recruited more than 1,000 women from prenatal clinics
in South Carolina. The women were between 21 and 34 years old, didn't
smoke, didn't have diabetes and were only pregnant with one baby.
Cholesterol levels were measured at about the 17th or 18th week of
pregnancy.

Overall, 118 of the women had low cholesterol levels mid-pregnancy and
940 women had levels higher than 159 mg/dL.

The study found that white women had five times higher odds of
delivering prematurely if they had low cholesterol. There was no
association between cholesterol levels and preterm delivery in black
women, according to the study.

However, for both races, babies weighed an average of 150 grams less
(about one-third of a pound) when born to mothers with low
cholesterol. Additionally, babies born to mothers with low cholesterol
levels were about twice as likely to have a small head circumference.

Muenke said the low cholesterol levels are likely caused by a
combination of genetics and nutrition. According to the study authors,
the low cholesterol levels may stem from poor diet and nutritional
deficiencies. What isn't yet known is if raising cholesterol levels in
these women would have a positive effect on the baby's health.

"I wouldn't recommend routine screening for cholesterol in pregnant
women right now," cautioned Welch. "It would increase health care
expenditures tremendously without a known benefit. This was a first
study; others need to done. We also need to find some explanation of
why it's taking place only in white women and not in black women."

"What this study does suggest is that diet in pregnancy is important,
and that not paying attention to nutrition could be harmful," said Welch.

Muenke agreed, adding that, "At this point, the message is really to
'stay tuned' for a repeat study. In the meantime, talk with your
obstetrician about a healthy lifestyle, including exercise and healthy
nutrition."

More information

To learn more about proper prenatal nutrition, visit the National
Women's Health Information Center.