Trusted Information for Healthy Pregnancies
37 weeks
Omega-3 Supplements Don’t Reduce Risk of Preterm Birth
Jan 28th
Omega-3 fatty acid supplements are believed to have many health benefits, but the one thing they can't do is help women with a history of delivering their babies early carry their next child to full term, new research finds.
"The omega-3 did not add any benefit," said study author Dr. Margaret Harper, an associate professor of obstetrics and gynecology at Wake Forest University School of Medicine, Winston-Salem, NC. The study appears in the February issue of Obstetrics & Gynecology.
Harper and her colleagues randomly assigned 852 pregnant women with a history of a preterm birth either to get a daily omega-3 supplement or a placebo beginning about week 16 to 22 and continuing through week 36 of gestation.
All women also received weekly intramuscular hormone injections of hydroxyprogesterone caproate, which has been shown to improve the chances of carrying a baby to term, Harper said.
Her team followed up to see which women delivered before 37 weeks. Full-term is defined as 37 weeks of completed gestation.
Delivery before 37 weeks occurred in 37.8 percent of those taking omega-3, and 41.6 percent of those in the placebo group, a small difference.
Prematurity is the leading cause of newborn death, the authors write in the report, and it is increasing in the United States. A woman who delivers one baby before term is more likely to deliver future babies early.
Harper's team decided to study the value of the omega-3 supplements after conflicting findings about the value of the supplements for women at high risk of premature delivery. For those at low-risk, she said, the findings seem to agree that omega-3 supplements don't further reduce the risk of preterm birth.
A recent large review of published studies found only one that showed benefit of the supplements in high-risk women, she said.
According to Harper, omega-3 fatty acids, when metabolized, are converted to much less potent biochemicals called prostaglandins, which make the uterus contract, than are omega-6 fatty acids -- also essential fatty acids but typically over-eaten in Western diets. Adding omega-3s to an omega-6-heavy diet, so the thinking went, might result in better chances of carrying the baby to term.
Omega-3 supplements, in other research, have been found to help heart health, to lower blood pressure and to reduce the risk of abnormal heartbeats.
But in Harper's study, she also noted that women getting omega-3 supplements were more likely to give birth to a baby with respiratory distress syndrome (RDS). While 59 babies (13.9 percent) of those in the omega-3 group had RDS, only 35 (8.7 percent) of those in the placebo group did. In other words, the omega-3 mothers' babies were 1.6 times more likely to get RDS than infants born to mothers taking placebo. It's the first time such a finding has been reported in clinical trials, the authors wrote.
"While the study's results showed no difference, there is early evidence that omega-3 fatty acids are beneficial for fetal brain development, so women should still consider taking them, in conjunction with their doctor's advice, despite what seems to be little benefit for the reduction of spontaneous preterm birth."
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Birth Weights Are Falling in U.S.
Jan 21st
Mothers are giving birth to lighter babies in the U.S., and no one is quite sure why.
This finding, published Thursday in the Journal of Obstetrics and Gynecology, has potentially troubling public-health implications, if the trend continues. Low-birth-weight babies are at higher risk for a host of health problems.
Between 1990 and 2005, the birth weight of full-term babies in the U.S. declined nearly two ounces to an average of seven pounds and 7.54 ounces, a reversal of a trend that had seen birth weights climb steadily since the 1950s, according to the study. They were also born 2.5 days earlier on average in 2005 than in 1990, the study said.
The decrease in weight—based on an analysis of nearly 37 million non-multiple births from a national database—isn't likely to affect the health of the average baby in the study, according to researchers. But the data showed a 1% increase in the number of the lowest-weight babies and suggested the birth-weight decline didn't stop in 2005.
These data suggest that it may be important for medical professionals to pay attention to the weight of babies born around 37 weeks and 38 weeks, as well as those considered pre-term, or less than 37 weeks, according to Joann Petrini, senior adviser at the March of Dimes and assistant research director at Danbury Hospital in Connecticut, who wasn't involved in the study.
Researchers also found a 2% decrease in the number of babies considered large—those over the 90th percentile of weight for gestational age—which is a positive, according to Dr. Oken. Large babies can experience more birth trauma and cause more birth injury to the mother.
The lower-birth-weight trend could not be explained by common factors like how much weight mothers gained during pregnancy, whether the delivery was induced or by cesarean section, prenatal care, or common maternal-health issues such as smoking and hypertension, researchers said.
Researchers also repeated their analysis in a sample of low-risk women—healthy, educated Caucasians in their mid-to-late 20s—and found that the decrease in birth weight was even more pronounced, suggesting that the trend isn't the result of changes in the population of mothers.
Other investigators also have begun to note the same trend. "There's no question" about the change in birth-weight pattern, said Michael Kramer, scientific director of the Institute for Human Development and Child and Youth Health at the Canadian Institutes of Health Research, who wasn't involved in the study.
"It is a new trend," he said. "We really don't know why the birth weight has decreased." A similar pattern has been observed in Canada, he said.
Some potential factors that weren't examined in this study include better control of gestational diabetes—when a mother develops diabetes during pregnancy—and more physical activity during pregnancy, said Dr. Kramer.
Babies considered too large, as well as too small, tend to have more health problems in the long run. The optimal size for a newborn is around 4,000 grams, or roughly 8.8 pounds, according to Dr. Kramer. The average baby in the study was found to be smaller than optimal. In 1990, the average birth weight was 3,441 grams, and in 2005 it fell to 3,389 grams, according to the study.
Babies born too small tend to have higher blood pressure and a greater risk of diabetes in the long run, said Dr. Oken.
From the 1950s until the 1980s, birth weights had increased as a result of increases in mothers' weight and how many pounds they gained during the pregnancy, as well as reduced smoking and older maternal age, according to Dr. Kramer.
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Hormone testing may help doctors predict abnormal childbirth
Dec 31st
Testing for low levels of a thyroid hormone shortly before childbirth may help physicians identify women who will require special care during delivery, new research indicates.
Specifically, a study published in the December 23 issue of Clinical Endocrinology, sought to examine whether thyroid hormone levels in the late stages of pregnancy are associated with the head position of a fetus shortly before childbirth, Health Day News reports.
The team of researchers examined the thyroid levels of 960 expectant Dutch mothers and found that those with higher levels of the hormone T4 about 9 months into pregnancy were more likely deliver a baby in the normal delivery position - head first with the fetus facing the mother's back at the start of labor.
Women with lower levels of the hormone more commonly needed assisted delivery because of an abnormal fetal head position, according to the news source.
"We believe that the relationship between thyroid hormone levels and fetal presentation at birth may be explained by recent findings that motor development in children is related to low maternal thyroid hormone concentration during pregnancy," Victor Pop, professor at the University of Tilburg in the Netherlands, told HealthDay News.
According to the Coalition for Improving Maternity Services, almost 32 percent of U.S. births in 2007 took place via cesarean section - a 50 percent increase since 1996.
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Pregnant women develop emotion-reading superpowers
Dec 14th
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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Mothers’ Genes Important in Preterm Birth Risk
Dec 9th
A mother's genes may be an important factor in the risk of preterm birth, two new studies suggest.
Past research has shown that genes likely play a role in a pregnant woman's odds of delivering prematurely - before the 37th week of pregnancy.
The risk is increased, for example, among women who were themselves born prematurely or have a sister who ever gave birth preterm, And findings from twin studies suggest that up to 40 percent of preterm deliveries involve some genetic susceptibility.
But little is known about the specifics of how genes influence preterm labor.
The two new studies, reported in the American Journal of Epidemiology, suggest that the mother's genes - rather than genes affecting fetal development that are inherited from both parents - are key.
In one study, Danish researchers analyzed national database information on more than 1 million singleton births in Denmark between 1978 and 2004. They found that, not surprisingly, women with a history of preterm delivery were at increased risk of having a subsequent early birth.
But the risk was also elevated among women with a mother, sister or half-sister (born to the same mother) who had delivered prematurely. Compared with women without such a family history, these women were 60 percent more likely to have a preterm birth.
In contrast, preterm births among female members of the father's side of the family, or among the female partners of a woman's male relatives, had no bearing on a woman's own risk of premature delivery.
The findings were similar in the second study - this one of more than 989,000 births in Sweden between 1992 and 2004. Researchers found that sisters of women who had delivered preterm had an 80 percent higher risk of early delivery, versus women without that family history.
There was no evidence of an increased risk, however, when a brother's partner had delivered prematurely. Nor was there evidence that the increased risk shared by sisters was explained by non-genetic factors that could influence the chances of preterm delivery, like smoking or lower education levels.
Overall, the researchers estimate that mothers' genes account for one-quarter of the variation in preterm delivery risk across the population. In contrast, fetal genes - which are inherited from both parents - showed little influence.
The vast majority of women in the studies did not deliver early, regardless of family history. In the Danish study, for example, about 7 percent of women with a sister who had delivered prematurely had a preterm birth themselves; that compared with 4.5 percent of women whose sisters had no history of preterm delivery.
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