In the largest study of its kind, researchers find that the risk of severe breathing problems rises significantly in babies born prematurely, even those born in the so-called late preterm period.

Health experts consider babies born at or after 37 weeks' gestation to be full term, and those born between 34 weeks and 37 weeks to be late preterm. (Preterm is defined as less than 34 weeks' gestation.) Many previous studies have shown that compared with full-term babies, those who are born too early are at higher risk of dying shortly after delivery and are more likely to suffer neonatal complications that require lengthy stays in the hospital.

In the new study, Dr. Judith Hibbard at University of Illinois also found that babies born at 34 weeks were 40 times more likely to have respiratory distress syndrome, a breathing difficulty that often requires a ventilator, than babies born at 38 weeks or later.

Even at 37 weeks' gestation — the point at which mothers may ask for an elective Cesarean section or induced delivery — babies are three times more likely than full-term infants to have respiratory abnormalities at birth. "That's a remarkably increased risk," notes Hibbard, who worked with the Consortium on Safe Labor, a group of 19 hospitals that contributed volunteers and data to the study. "And I have to admit, much higher than I was expecting."

Despite the accepted 37-week full-term cutoff, the American College of Obstetricians and Gynecologists officially recommends that babies not be delivered (unless medically necessary) until after 39 weeks. Yet some 9% of all deliveries in the U.S. still occur just shy of 37 weeks, and a recent study found that as many as 23% of late pre-term births — between 34 weeks and 37 weeks — occur for no documented medical reason.

Hibbard says she was surprised by the high rate of health problems she and her team found in this group, since advances in neonatal care have allowed more high-risk babies to survive and eventually thrive after being born too early. But the fact that respiratory distress syndrome continued to occur in premature infants at 40 times the rate in full-term babies highlighted how risky premature delivery can be. At 34 weeks, infants' lungs and respiratory systems are not fully developed, making it difficult from them to survive outside the womb.

With every week of gestation after 34 weeks, however, Hibbard found that rates of complications dropped — by 40 weeks, only 0.3% of babies showed signs of respiratory distress. While 67% of babies required admission to the neonatal intensive care unit at 34 weeks, only 7% of those born at 38 weeks required the same care. Further, 1.5% of babies delivered at 34 weeks developed pneumonia, compared with practically none of those born at 38 weeks. "To be honest, with studies like this, it's hard to justify deliveries before 39 weeks," says Dr. Richard Waldman, president of the American College of Obstetricians and Gynecologists.

Both Hibbard and Waldman stress that there may be valid medical reasons for delivering a baby early — if the mother has preeclampsia, the dangerously high blood pressure that can occur during late pregnancy, for example, or if the baby is no longer growing properly in the womb — but that doctors should discourage elective delivery before 39 weeks.

The new study adjusted for many of the major contributors to prematurity, such as the mothers' weight and history of other medical conditions, including preeclampsia and diabetes, but the relationship between early delivery and risk of respiratory distress in the babies remained. "I know mothers may request early delivery for a lot of reasons," says Hibbard. "But I hope the obstetrician will pull this study out and say, 'Look, early delivery is not a good idea unless there is really a strong medical indication.'"

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PregnancyWeekly.com

Any weight gain during the first 14 weeks of pregnancy -- or more than a pound a week between weeks 14 and 36 -- raise the odds your child will show signs of heart disease by age 9.

The findings come from the U.K. Avon study, which is following the health of nearly 14,000 children born from April 1991 through December 1992. The study, by University of Bristol researcher Abigail Fraser, PhD, and colleagues, focuses on more than 8,500 mother/child pairs for whom detailed data were available.

Women who were overweight before becoming pregnant were more likely to have overweight or obese children.

But regardless of a woman's pre-pregnancy weight, weight gain during pregnancy affected the child's weight -- and at age 9, the child's risk of having high body fat, low levels of good HDL cholesterol, a big waistline, high blood pressure, and other risk factors for heart disease.

Children's heart risk increased with any weight gain during the first 14 weeks of pregnancy, and with any weight gain over 1.1 pounds per week during weeks 14 to 36 of pregnancy. The more weight a woman gained during these times, the higher her child's heart risk.

Weight gain after week 36 of gestation was not linked to heart risk in a woman's offspring.

What's going on? Fraser and colleagues suggest that the reason why these kids already have a high heart risk by 9 years of age is their fat mass. But exactly why children tend to be fat if their mothers gain too much weight during pregnancy isn't clear.

One thing is clear, comments obstetrician/gynecologist Jennifer Wu, MD, of New York's Lenox Hill Hospital.

"In order to help ensure healthier futures for their children, women considering childbearing should try to achieve ideal body weight pre-pregnancy and to adhere to recommended weight-gain guidelines," Wu says in a statement released by the Lenox Hill press office. Wu was not involved in the Fraser study.

The Fraser study appears in the June 15 issue of Circulation, a journal of the American Heart Association.

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PregnancyWeekly.com

The rising trend of expectant mothers being involved in every aspect of planning their births has had an unintended consequence - a rise in pre-term deliveries.

"It never would have occurred to me or anyone I knew to think you had any kind of control over when the baby would come out," said Laura Crawford, who gave birth more than a decade ago.

Crawford, producer of the Kentucky Educational Television documentary "Born too Soon," said the increasing incidence of what is called late pre-term births is among the topics explored in the film.

Prematurity rates in the nation have increased quietly over the past two decades, according to public health officials. The premature-birth rate in Kentucky is 15.2 percent, and it's rising faster than the national rate, which is 12.7 percent. Kentucky has one of the highest rates of pre-term births, trailing only Louisiana, Alabama, Mississippi and South Carolina.

Some of Kentucky's rise is related to some not-so surprising subjects, including the rate of maternal smoking (more than twice the national average), poverty and environment.

Other reasons are more surprising. They include the rise in scheduling births.

It's just within the last three or four years that the scope of the problem of late pre-term births - babies born between 34 and 36 weeks' gestation - has become apparent, said Dr. Ruth Shepherd, division director for maternal and child health in Kentucky's Department of Public Health. Roughly 10 percent of all babies born in Kentucky fall into the late pre-term category.

Ideally, she said, babies shouldn't be delivered before 39 weeks.

Often, there are legitimate reasons for early delivery, especially if the health of mother or child is at risk.

Increasingly, choices are made for reasons other than health. Delivery might be scheduled to coincide with grandparents' dates of arrival from out of town, or before Dad must ship out for Iraq.

There are several complicating factors, Crawford said. The documentary states that people tend to underestimate the impact of premature births, especially late pre-term births. They tend to overestimate how accurately a due date can be determined.

Shepherd said there can be real consequences. They can include immediate physical challenges, including underdeveloped lungs and long-term problems involving learning and behavioral disabilities, for example.

And even if a mother gets an ultrasound within the first 16 weeks - the best way to accurately determine the due date - the date can be off by two weeks either way.

Those two weeks can be crucial, she said.

"It's an issue of planning and control," she said. Planning is good. The Centers for Disease Control and Prevention recommends that mothers have a birth plan. But, Shepherd said, "you can take it too far if you don't pay attention to the science."

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PregnancyWeekly.com

Raging hormones during pregnancy prompt mood swings, but may also lead to a heightened ability to recognize threatening or aggressive faces. This may have evolved because it makes future mothers hyper-vigilant, yet it could also make them more vulnerable to anxiety.

Previous studies have suggested that a woman's ability to correctly identify fearful or disgusted facial expressions varies according to her stage of the menstrual cycle, with perception heightened on days associated with high levels of the hormone progesterone. Since levels of progesterone and other hormones rise dramatically in late pregnancy, Rebecca Pearson and her colleagues at the University of Bristol in the UK investigated whether the ability to read faces varies during pregnancy.

They asked 76 pregnant women to assign one of six emotions to 60 computer-generated faces before the 14th week of pregnancy, and again after the 34th week. Faces expressing happiness and surprise tended to be correctly assigned at both stages of pregnancy, but for faces expressing fear, anger and disgust, the accuracy rates were higher in late pregnancy.

This may increase the chance that the woman will spot potential threats to her and her fetus, and prime her to be hyper-vigilant once she becomes a mother. But it could have a downside. Pearson points out that people with clinical anxiety are also better at identifying negative emotions in faces. Pregnant women aren't clinically anxious, but "they might interpret negative or emotional things around them in a slightly more sensitive way", she says.

The finding builds on a recent study by Ben Jones of the University of Aberdeen in the UK who found that pregnant women - and women in stages of the menstrual cycle where progesterone levels spike - are better at identifying faces showing signs of sickness. "It's preventing them from becoming sick by interacting with people who are ill," he says.

The next step will be to examine whether pregnant women and new mothers are also more sensitive to emotional cues in babies' faces, Jones says.

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PregnancyWeekly.com