Why are More Boys than Girls Being Born?
94,232 more boys than girls were born in 2002. This is the
latest finding of the Centers for Disease Control and Prevention's
(CDC) "Trend Analysis of the Sex Ratio at Birth in the
United States," which measured the sex ratio at birth
for more than the past 60 years.
If that statistic surprised you, you'll be even more surprised
to learn that an average of 91,685 more male babies have been
born each year than females from 1940 to 2002. That means
a total of 5,776,130 more boys were born during that period.
Even though more boys are born, some say male births
are actually decreasing.
The CDC pointed out a few other interesting findings on the
ratio of boys to girls, too:
Older Moms and Teen Moms: Women in their 40s had the
lowest ratio of boys to girls while late-teen moms had the
Number of children: The more children a woman has,
the more likely she'll have an equal number of girls and boys
Ethnicity: Chinese women had the highest ratio of
boys to girls, followed by Filipino women, while American
Indian moms had the lowest.
Other factors that may impact the ratio include older fathers,
stress, environmental toxins and lower maternal weight, says
What's the Norm?
During development, boys are more fragile than girls.
Although these statistics may seem alarming at first glance,
they are well within the "normal" worldwide ratios,
even at the extremes. Globally, there
are about 105-107 boys born for every 100 girls.
At the highest sex birth ratio in the United States, which
occurred in 1946, there were about 105.9 boys born per 100
girls; and at the lowest sex birth ratio (in 2001), there
were about 104.6 boys born per 100 girls. There were 104.8
boys born in 2000 for every 100 girls.
For comparison, in China, where couples are only allowed
to have one child, the gender balance has become alarmingly
skewed and millions of men may be forced to remain bachelors
because of the shortage of women.
"This is a seriously dangerous ratio," said Ren
Yuling, a delegate to the Chinese People's Political Consultative
Committee. "The numbers mean that some people will never
have their needs for a spouse met, so they move into dangerous
Just what is China's sex birth ratio?
In 2000, there were 116.9 boys born for every 100 girls.
Why are more boys naturally born than girls? The New York
Times offered some clues in an article called, "The Weaker
Sex." Although more boys are born,
it appears they may be more susceptible to a host of diseases,
injuries and more, and soon women actually outnumber men.
Here are just a few of their findings:
Facts on Females Living Longer &
- Male births slightly outnumber female
births, but boys have a higher death rate if born
premature: 22 percent compared with 15 percent for
- Overall, more newborn males die than
females (5 to 4).
- Sudden infant death syndrome is one
and a half times more common in boys than girls.
- As teenagers, boys die at twice the
rate of girls.
- Men have fewer infection-fighting
T-cells and are thought to have weaker immune systems
- By the age of 36, women outnumber
- Stroke, cancer, diabetes, heart disease
and accidents--all among the top causes of death--kill
men at a higher rate than women.
- American men typically die almost
six years before women do.
- By the age of 100, women outnumber
men eight to one.
During fetal development "the male sex is clearly the
more fragile one," said Bruce B. Allan, an obstetrician-gynecologist
in Calgary, Alberta Canada.
Is the Number of Boys Actually DECREASING?
Between 1970 and 1990, the proportion of male births
decreased 1 percent.
The CDC study above doesn't touch on another CDC finding,
this one released in 2002, that birth rates overall had hit
an all-time low. The birth rate fell to 13.9 per 1,000 persons
in 2002, down from 14.1 per 1,000 in 2001. This is a full
17 percent decrease in births from 1990, when rates reached
16.7 per 1,000 people.
Take that finding, coupled with the fact that a study by
Allan and his colleagues found that, from 1930 to 1990, the
male sex ratio had dropped by about 1 boy per 1,000 births.
Though older parents, fertility drugs and certain diseases
have all been linked to an increasing proportion of female
births, Michelle B. Gottlieb of the World Resources Institute
(WRI), says the findings "suggest that avoidable, [likely]
environmental, factors may be playing a role."
Pollutants that mimic human hormones,
including dioxin have become ubiquitous in the environment
and may be affecting births. For instance, in 1976,
an industrial accident released high levels of dioxin into
the environment near Seveso, Italy. Of the nine couples who
received the highest exposure, 12 daughters were born--and
no sons. Among four couples who had lower blood levels of
dioxin, "The male-female ratio approached normal,"
said Larry L. Needham of the Atlanta CDC.
Devra Lee Davis, a program director at WRI believes that
the declining male birth ratio "should
be viewed as a sentinel health event," an indicator that
environmental hazards difficult to detect by other means do
exist and should be dealt with.
But there are other theories too. A study in the journal
of the American Medical Association found that high exposures
to certain pesticides could interfere with a father's ability
to produce sperm cells with Y chromosomes--the kind needed
And, another study found that women who eat PCB-contaminated
fish (PCBs, or polychlorinated biphenyls, can mimic female
sex hormones) are less likely to give birth to boys. The women
who were exposed to the highest levels of PCBs (just by eating
contaminated fish) had about 50 percent fewer boys compared
with women who had been exposed to the lowest levels.
So even though over 94, 000 more boys than girls are born
in the United States each year, it seems it's the boys we
need to worry about--in the two decades between 1970 and 1990,
the proportion of male births went down an entire 1 percent
What You Don't Know Can Indeed Hurt You
Center for Health Statistics June 14, 2005
Today: China Thrown Off Balance as Boys Outnumber Girls
York Times: The Weaker Sex
News Online: Why are Boys Birth Rates Falling?
Have All the Boys Gone?
Fish Reduce Male Birth Rate