WEDNESDAY, May 21 (HealthDay News) -- At least some of the biological risk for childhood asthma and allergies traces back to the womb, new research suggests.

Both the order of birth and even the way a baby is delivered have a significant impact on the long-term strength of a child's allergic defenses, scientists say.

The findings were presented Wednesday during the American Thoracic Society's International Conference, in Toronto.

At the meeting, one team of scientists said it had evidence indicating that when a specific genetic marker for allergic and asthmatic development is present among a first-born child, it appears to raise the risk for allergic conditions as far as 10 years down the road. However, when the exact same marker is present in a family's second or third child, the gene seems to have exactly the opposite effect -- actually lowering such risk.

"This is the first time it has been demonstrated that birth order can affect the behavior of genes related to asthma and allergies, and that birth order can therefore affect the risk for developing one or the other," said study author Dr. Wilfried Karmaus, a professor in the department of epidemiology and biostatistics at the University of South Carolina in Columbia.

On a second front, another team of researchers suggested that regulatory cells associated with proper immune function may be impaired in babies delivered by Caesarean section.

"We found a dysfunctional cellular response in the normally protective immune system among C-section babies," observed Dr. Ngoc Ly, an assistant professor of pediatrics at the University of California at San Francisco. "And although more work needs to be done to follow how long this response might endure, we think this disrupted immune pathway may influence the development of asthma later on."

To explore the relationship between birth order and asthma/allergy risk, Karmaus and his team tracked more than 1,200 newborns from Great Britain's Isle of Wight.

After recording birth orders, the researchers tested each newborns allergic status by examining indicators present in umbilical cord blood. As well, they conducted standard skin prick allergy tests at both age 4 and age 10.

The authors found that among firstborn children, the presence of a particular gene strain -- known as the IL-13 gene variant -- was associated with a higher risk for having an "allergic response." This link continued to persist a decade later.

By contrast, among second or later-born children no such association between IL-13 and higher risk was found. In fact, the role of IL-13 seemed to "switch over" to that of a risk protector.

"The fetus is, in effect, a foreign body," noted Karmaus. "And a foreign body can be exposed to a lot of immune arousal or not, depending. So we think that something during pregnancy -- probably the immune system of the mother -- stimulates the IL-13 gene to act differently, depending on birth order. We haven't shown how this works yet, but that's the idea."

Karmaus suggested that the finding could theoretically lead to the crafting of interventions -- perhaps therapeutic, perhaps simply lifestyle changes -- which could reduce the allergic response risk for firstborns.

Meanwhile, Ly and her colleagues explored similar risks associated with Caesarean sections by analyzing the cellular immune regulatory activity present (in the form of so-called treg cells) in the umbilical cord blood of 50 babies born by Caesarean and 68 babies delivered vaginally. All the babies had a least one parent with allergies and/or asthma.

The authors found that among C-section babies, treg cells were more likely to fail to operate properly, raising the risk for the early onset of immune system disruption. This, in turn, may increase the likelihood that a child could grow up to develop an allergy or asthma.

Ly and her team said that the suggestion that the manner of delivery could actually influence immune system development and ultimately asthma/allergy risk could be due to the fact that vaginal labor provides beneficial exposure to birth canal microbes that simply aren't available to a C-section baby.

"But still I think it's important to reiterate that while this is interesting research, it is a small study and the first of its kind," noted Ly. "So there is much more follow-up work that needs to be done to see if these newborns in fact start developing symptoms of asthma or allergies as they grow."

Approaching the root causes of asthma and allergies from yet another angle, a third team of German researchers presented findings suggesting that mothers who visit farms and drink farm milk confer a anti-allergy benefit to their future babies.

The study involved 18 farming mothers and 59 non-farming mothers. Farm-based mothers appeared to give birth to babies with better-functioning treg cells.

More information

For details on childhood asthma, visit the American Lung Association  .

TUESDAY, May 20 (HealthDay News) -- U.S. blood collection centers face a conundrum: At a time of decreasing blood donations, a new study shows that an important source of current and future donations, 16- and 17-year-olds, are more likely to bruise, faint or experience other complications when they donate.

That means this critical pool of young donors may be less likely to give in the future, experts say.

"Most donors in all age groups have uncomplicated donations," stressed Dr. Anne Eder, executive medical officer of biomedical services at American Red Cross National Headquarters in Washington, D.C. "What was surprising was how much young donors contribute to the blood supply. The other important finding was that 16- and 17-year-olds were more likely to return to give blood again, but even a minor reaction like dizziness or other symptoms will reduce the likelihood that they will donate again."

Eder is lead author of a study published in the May 21 issue of the Journal of the American Medical Association.

Due to factors including increased restrictions -- such as screening for West Nile virus and Chagas disease -- only an estimated 38 percent of the U.S. adult population is currently eligible to donate blood.

Between 2001 and 2004, there was a 0.2 percent decrease in blood donations in the United States, even though the number of transfusions rose by 2 percent.

Luckily, donations from young people, who are less likely to have infectious diseases, have been on the rise. By 2005, donors aged 16 to 19 represented 14.5 percent of annual donation, with 16- and 17-year-olds contributing 8 percent of the units collected by the Red Cross. About 80 percent of these donations come from high school blood drives. At the same time, the rate of donations from older individuals has declined.

The authors estimated that if 16-year-olds nationwide had the opportunity to donate blood, an additional 200,000 units of blood could be added to the current annual collection of 15 million units.

Most states allow blood donation by 17-year-olds without parental consent. Only 22 states or U.S. territories allow donation by 16-year-olds with parental consent, and just two allow donation by 16-year-olds without parental consent. The Red Cross does not accept donations from 15-year-olds, requires parental consent for 16-year-olds and follows state regulations for 17-year-olds.

However, "there is an ever- increasing demand for blood donations with a decreasing pool of donors," said Dr. Peter Richel, head of pediatrics at Northern Westchester Hospital in Mt. Kisco, New York. "Therefore, what's big is high-school blood drives. There's a sense of community and learning to give."

But will that giving continue if fainting, bruising and other problems persist?

The authors of this study analyzed data collected from nine American Red Cross blood centers that routinely collect blood from 16- and 17-year-olds.

Complications occurred in 10.7 percent of 16- to 17-year-olds and 8.3 percent of 18- to 19-year-olds. That's compared to a rate of only 2.8 percent for adults aged 20 and over.

Overall, 16- and 17-year-old donors were three times more likely to experience complications compared to donors aged 20 and above, first-time donors were almost three times as likely to experience complications compared to repeat donors, and females were almost twice as likely to experience donation-linked complications compared to males. There were some regional variations as well, the team said.

Injuries related to fainting (including concussion, stitches and broken jaws) were more than twice as frequent in 16- and 17-year-olds as in 18- and 19-year olds and more than 14.46 times as likely than in the over-20 group.

These incidents can influence the willingness of young donors to donate blood again, the researchers found. Only 52 percent of 16-year-olds who experienced a problem, no matter how minor, returned for a repeat donation within a year, versus 73 percent of those whose donation went smoothly.

"We want donors to have a good experience, and there are a number of ways to do that. Every step is important," Eder said. "We collect these safety data so we have a baseline and can monitor and further our effort to improve the donor's experience."

Steps already well-known to reduce donation-linked problems include drinking lots of water, getting a good night's sleep and eating a nutritious meal before hooking up to the IV, experts say.

More information

For more on giving the gift of life, head to the American Red Cross  .

SUNDAY, May 4 (HealthDay News) -- New research shows that only half of American mothers intend to have their teenaged daughters vaccinated against human papillomavirus (HPV) if the girls are under the age of 13, despite government guidelines that suggest the opposite.

HPV, which is sexually transmitted, is the primary cause of cervical cancer. The first vaccine against the virus, Gardasil, was approved in 2006. The U.S. Centers for Disease Control and Prevention currently recommends that 11- and 12-year-old girls be targeted for this vaccine, as most girls of this age are not yet sexually active, have not yet been exposed to HPV, and will therefore achieve maximum protection.

However, this study suggests that many mothers aren't willing to follow those recommendations.

"Mothers had a lower intention to vaccinate [younger] daughters," said study author Dr. Jessica Kahn, an associate professor of pediatrics at Cincinnati Children's Hospital Medical Center. "This presents a challenge, and provides us with an opportunity to educate mothers about the importance of vaccinating girls under 13 years of age because the vaccine will have a greater health impact if given before 13."

Kahn will present the findings Sunday at the Pediatric Academic Societies' annual meeting in Honolulu.

About 10,000 new cases of cervical cancer are diagnosed in the United States each year, with about 4,000 women dying of the disease annually.

Three-quarters of U.S. women will be exposed to HPV at some point in their lifetime and, at any one time, one-quarter have been infected.

According to one estimate, giving the vaccine universally would eliminate about 70 percent of cervical cancer cases. Gardasil protects against most, but not all, types of HPV that cause cervical cancer.

This study is the first national survey of its kind and also the first to measure attitudes towards the vaccine since it was approved by the U.S. Food and Drug Administration in 2006.

Forty-nine percent of almost 10,000 respondents intended to vaccinate a daughter if she were 9 to 12 years old; 68 percent intended to vaccinate if the daughter was 13 to 15 years old; and 86 percent said they would vaccinate if the daughter was 16 to 18 years of age.

Specific beliefs about HPV vaccine were the most powerful predictor of one's intention to vaccinate one's 9-to-12-year-old daughter.

The belief that really stood out was that the vaccine would protect the daughter against cervical cancer. "That was not at all surprising to me," Kahn said. "[Other] studies have shown that the most powerful factor driving mothers' decisions is the desire to protect a child from harm."

The next most powerful predictor were beliefs that the vaccinations would not cause a child to engage in riskier sexual behaviors.

"That implies we need some studies to prove or disprove this concern," Kahn said. "It also is going to be important for clinicians to address that head on with parents."

If a clinician recommended the vaccine, the mom was more likely to decide to vaccinate her daughter.

Mothers were also more likely to go for the vaccine if they thought their daughter was at risk for HPV.

All of these factors could be incorporated into messages, including those seen in brochures and posters about HPV and the vaccine, Kahn said. She was also lead author of a paper appearing in the May issue of Obstetrics & Gynecology that found that interventions which address personal beliefs about the HPV vaccine as well as system-wide barriers to vaccination could lead to higher vaccination rates.

"This shows that there's a difficulty in having mothers recognize that their children will become sexually active at a relatively young age," said Dr. Jay Brooks, chairman of hematology/oncology at Ochsner Health System in Baton Rouge, La. "It's a process and it's an attitudinal change that has to occur."

More information

The U.S. National Cancer Institute has more on HPV and cervical cancer.

MONDAY, May 5 (HealthDay News) -- Children who wet their beds frequently have elevated levels of a heart hormone that helps regulate levels of fluid around the heart, a new study finds.

Additionally, children who habitually snore are about three times as likely to wet the bed as children who don't snore, but the severity of snoring appears to have little effect on the risk of bed-wetting, according to the research, which is published in the May issue of Pediatrics.

"Our findings were really an eye-opener," said study co-author Dr. David Gozal, director of the division of pediatric sleep medicine at the University of Louisville, in Kentucky. "Why children with bed-wetting have high levels of this hormone; that will require a bit more research."

About 9 percent of boys and 6 percent of girls at age 7 have trouble sleeping through the night without wetting the bed, according to the U.S. National Institutes of Health. The problem -- which affects about 5 million American children -- runs strongly in families. Nighttime bed-wetting, which is also called enuresis, is not the fault of the child or parent. For some reason, the child's brain isn't responding to normal cues to wake up and empty the bladder.

Because so many children who snore seem to also wet the bed, Gozal and his colleagues wanted to investigate the connection between the two problems.

The researchers reviewed almost 18,000 surveys completed by parents of 5- to 7-year-old children to see how many were habitual snorers or had problems with enuresis. From that group, they found that 1,976 children -- about 11 percent -- were habitual snorers. Fifty-three percent of those with habitual snoring were boys. About 27 percent of that group also wet the bed. Nearly 90 percent of those who wet the bed were boys. Among non-snoring children, just 11.6 percent wet the bed. As with the snoring group, almost 90 percent of those with enuresis were boys.

"The risk of bed-wetting for children who snore was about threefold," said Gozal.

But, the researchers also found that the severity of snoring didn't appear to change the risk of bed-wetting when they examined a smaller group of 60 children who wet the bed during sleep lab studies. Twenty of the children had obstructive sleep apnea; 20 had habitual snoring but no sleep apnea, and 20 didn't snore at all.

The researchers did find that levels of a heart hormone, brain natriuretic peptide (BNP), were raised in children who wet the bed. That finding would seem to be related to snoring, according to Gozal, because snoring causes the upper airways to contract, which makes the chest muscles work harder to pull in air, which in turn creates pressure on the airways and blood vessels, which causes blood to return to and dilate the heart. Then, too much fluid collects and needs to be released, which is one of BNP's functions -- to increase sodium and water excretion around the heart.

However, if snoring was responsible for the elevated BNP levels, a more serious snoring problem should have caused even higher levels of BNP, but that wasn't the case.

"Clearly, this is a complex mix," said Gozal.

What parents need to know from this study is that if your child is predisposed to bed-wetting, any additional factors, such a snoring, may make bed-wetting more likely. So, if your child snores and wets the bed, Gozal said that treating the snoring may help reduce bed-wetting.

"This is a great study, and it's nice to see some of the science behind the problem," said Dr. Sangeeta Chakravorty, clinical director of the pediatric sleep program at Children's Hospital of Pittsburgh.

"Parents should know that 15 percent of children get better every year with no intervention," she said, but added, if bed-wetting persists after a child is 5 years old and it happens more than three times a week, you should mention it to your child's doctor at the next well visit.

More information

To learn more about enuresis, visit the American Academy of Family Physicians  .