WASHINGTON (AP) _ ``It's a boy.''
Statistically speaking, that's what the majority of moms hear after giving birth.
Chances are he was born on a Tuesday. It was probably August. If she was typical, his mother was 24 years old, almost 25.
In 2001, it was more likely that she got prenatal care than in years past. Chances that she smoked during pregnancy dropped, too.
The trends are documented in the 2001 review of American births, released by the government on Wednesday.
The report found that teen births at another record low, the 10th year running that the rate fell.
The percentage of babies born prematurely reached a two-decade high, driven by an increase in twins and triplets.
And the percentage of Cesarean sections continued to climb, reaching nearly one-quarter of all births, the highest rate since data became available more than a decade ago. The rate has been on the rise for five years now.
Overall, 4,025,933 babies were born in the United States in 2001, a small drop from 2000.
Fifty-one percent of them were boys, which is usually the case though researchers aren't sure why.
It might be because, during certain times in a woman's menstrual cycle, the acid balance in her system is more likely to allow sperm with ``y'' chromosomes to make it to fertilization, said Paul Sutton, demographer with the National Center for Health Statistics, which produced the report.
It also may be nature's way of balancing the fact that boys and men are more likely to die than girls and women, he said. By the time babies reach their 30s, the genders are even, and by the time old age sets in, women outnumber men.
It's a lot of guess work, Sutton and his colleagues allow. Take time of the year _ August or September are almost always the most popular. Maybe it's because nine months earlier, cold weather began to set in.
``It's the winter months when people are holed up inside by a fire,'' said Joyce Martin, the report's lead author, offering one of several theories.
On a more serious note, health officials worry about the C-section rate. They had hoped to see it drop to 15 percent, contending that vaginal births carry a lower risk of medical complications for mothers. But the rates are climbing both for mothers who have never had a C-section before and for those who have.
Also disturbing: the rise in babies born prematurely, which is defined as less than 37 full weeks of gestation. The percentage of babies born that early rose to nearly 12 percent, the highest level since officials began tracking this category 20 years ago.
In a related finding, the portion of babies born dangerously little also rose, to 7.7 percent in 2001, an increase of 13 percent since the mid-1980s.
Some of the rise in premature and low birthweight babies can be traced to the increased number of multiple births; in these cases, babies tend to be born before their due date and are smaller than other babies. The number of older mothers and women who use certain fertility treatments are on the rise, and such women are more likely to have twins, triplets and even higher multiples.
Analysts said the increase could be a function of doctors opting to induce birth early because of complications with mother or fetus. Sometimes the mother has high blood pressure, which restricts blood flow to vital organs. The fetus may not be growing inside the uterus, usually because it is not getting needed oxygen and nutrients.
Both conditions can prompt a doctor to induce birth early, said Dr. Fredric Frigoletto, chief of obstetrics at Massachusetts General Hospital in Boston. He added that the decision is not always the right one.
``It's a very tense situation for both mother and doctor,'' he said. ``You're walking a narrow line, and if your judgment is off or the tests are misleading, it's easy to make the wrong decision.''
Overall, the rate of induced births, both early and on time, continued to climb, reaching one in five births last year. This rate has nearly doubled since 1989. The reasons are not always medical, Frigoletto said.
``Their parents or their in-laws are coming from far away, and if you can put this on a fixed timeline it seems to work well for everybody,'' he said. ``They often don't know what the downside is to having everything so structured and sounding so neat.''
The rise in prenatal care during the first trimester has been steady for a decade, particularly among Hispanic and black women. In 2001, 83 percent of women got timely prenatal care, up from 76 percent in 1990. More good news: the portion of women who smoked while pregnant continued a decline that began more than 10 years ago, reaching 12 percent in 2001.
Fewer teenage births and more older women having babies combined to raise the median age of childbirth. The typical first-time mother is now 24.8 years old, up from 22.1 years old in 1970.