In This Article
Subscribe to Health Updates
Baby Boys on the Decline; Pollution May Be Factor
May 28, 2008 02:50 PM
Some believe fewer boy births are the result of natural population swings, but others think pollution and stress are to blame.
Email This30-Second Summary
The ratio of baby boys to girls has been declining in the United States since 1970, with 17 fewer males for every 10,000 births, according to a study last year in the journal Environmental Health Perspectives.
Now, scientists are looking for causes.
Some experts say the shift is part of a natural, cyclical population pattern. But new research suggests that exposure to pollutants such as pesticides, mercury and lead may be damaging male fetuses, causing miscarriage, or affecting men’s testosterone levels, which play a role in determining a baby’s sex, causing fewer boys to be conceived.
Another emerging theory is that stress can damage Y-bearing sperm, reducing the chance of a boy being conceived.
But can environmental factors really affect the sex of a baby?
In April, a British study suggesting that a mother’s diet determines her baby’s sex raised skepticism as well as ethical concerns.
Although many theories abound, there is “relatively little a couple can do” to alter the chances of having a boy or a girl, writes Rob Shmerling for Harvard Health.
“If you have a strong preference for a boy or a girl, your options are limited. You could plan to have enough babies so both genders are eventually represented. Or it may be better to rethink your position and hope for a healthy baby of either sex,” he writes.
Now, scientists are looking for causes.
Some experts say the shift is part of a natural, cyclical population pattern. But new research suggests that exposure to pollutants such as pesticides, mercury and lead may be damaging male fetuses, causing miscarriage, or affecting men’s testosterone levels, which play a role in determining a baby’s sex, causing fewer boys to be conceived.
Another emerging theory is that stress can damage Y-bearing sperm, reducing the chance of a boy being conceived.
But can environmental factors really affect the sex of a baby?
In April, a British study suggesting that a mother’s diet determines her baby’s sex raised skepticism as well as ethical concerns.
Although many theories abound, there is “relatively little a couple can do” to alter the chances of having a boy or a girl, writes Rob Shmerling for Harvard Health.
“If you have a strong preference for a boy or a girl, your options are limited. You could plan to have enough babies so both genders are eventually represented. Or it may be better to rethink your position and hope for a healthy baby of either sex,” he writes.
Headline Links: ‘A Puzzle Over Fewer Boy Births’
Compelling evidence for new theories is that the steepest sex ratio declines in the world have occurred on the 3,000-acre Aamjiwnaang First Nation reservation in Canada, a site bordered by dozens of petrochemical, polymer and chemical plants. Although the population isn’t huge, “it’s important to look at the really big picture here, which is that there are global indications that something unusual is going on,” said Devra Davis, the lead author of last year’s report.
Source: The Chicago Tribune
Background: Baby boys on the decline
Last year, a University of Pittsburgh-led study found that the number of male births in the United States and Japan had decreased each year for the previous 30 years. The study found that significantly fewer boys than girls were born during the three decade span—135,000 fewer white males in the United States and 127,000 fewer males in Japan—and that an increasing proportion of fetuses that died were male.
Source: The Pitt Chronicle
A January 2006 story in Scientific American analyzes the potential societal reasons behind fewer male babies being born in times of stress: “It’s better to have a female than a male in stressful times,” explained statistician Ralph Catalano of the University of California Berkeley. He said that “weak” males are unlikely to survive to reproductive age or, if they do, are unlikely to be able to win mates over more robust males. “If you have a daughter, [her] reproductive success is not contingent on robustness because males are not as picky,” Catalano said.
Source: Scientific American
Related Topics: Affecting and choosing a baby’s sex
In April, a study suggesting that a mother’s diet can help determine the sex of her baby was met with skepticism, and raised ethical concerns. Researchers claimed that mothers who consumed a greater number of calories during their pregnancies, as well as those who ate at least one bowl of cereal per day, gave birth to more male babies.
Source: findingDulcinea
Pre-implantation genetic diagnosis (PGD)—initially created as a way to distinguish healthy embryos from those predisposed to genetic diseases during in vitro fertilization—is being used by parents to choose the sex of their child. Not everyone approves.
Source: findingDulcinea
Opinion & Analysis: The facts and the myths, and the strength of females
Rob Shmerling explains the facts behind gender selection for Harvard Health: “If the father provides an X chromosome, the baby will be female, and if he supplies a Y chromosome, the baby will be male,” as well as analyzes unproven theories regarding choosing a baby’s sex.
Source: MSN Health and Fitness (Harvard Health Publications)
Kathleen Parker analyzes the decline of baby boy births and the theories behind the shift in a piece called “Women Rule” in the San Francisco Chronicle. “Not only do women outlive men, but recent research shows that they’re also being born more often than in the past. The allegedly stronger sex, it turns out, is really the weaker and more vulnerable—from conception until death do us part,” she writes.
Source: The San Francisco Chronicle
Reference: Pregnancy
FindingDulcinea’s Web Guide to Pregnancy features the best online resources for learning about conception, what to expect during pregnancy and how to prepare for the baby’s arrival.
Source: findingDulcinea
Most Recent Beyond The Headlines
© 2008 Dulcinea Media, Inc.
