U.S. Twin Births Soar: CDC

WEDNESDAY, Jan. 4 (HealthDay News) — The birth rate for twins in
the United States has jumped by 76 percent since 1980, government health
officials reported Wednesday.

Most of the increase appears linked to new fertility treatments that
make it easier for older women to conceive, according to a report released
by the U.S. Centers for Disease Control and Prevention.

“The growth in twin birth rate has occurred in all age groups, although
the largest growth has been among older mothers,” said study lead author
Joyce A. Martin, an epidemiologist in the Division of Vital Statistics,
Reproductive Statistics Branch at CDC’s National Center for Health

One reason for the increase is that mothers have been a little older,
Martin said, “and women in their 30s are more likely to have a multiple

However, only about one-third of the rise in twin births is
attributable to the mother’s age, Martin said.

“Most of the increase is likely the result of fertility-enhancing
therapies, which is also more common among older mothers,” she said.

Other highlights of the report:

  • In 1980, one in every 53 babies was a twin; by 2009 that had risen to
    one in 30.
  • In 1980, the twin birth rate was almost 19 in 1,000 births; by 2009 it
    rose to more than 33 per 1,000 births.
  • Had the 1980 rate not changed, there would have about 865,000 fewer
    twins born over the last 30 years.
  • The rate of twin births increased in most states by at least 50
  • In the past 30 years, twin birth rates almost doubled among women ages
    35 to 39 and more than tripled among women 40 and older.

While most twins are delivered safely and grow up fine, twin birth does
carry added danger to both infant and mother, Martin noted. “The growth in
twinning has added to the number of infants that are born at risk,” she

“More than half of twins are born low birthweight, compared to less
than 10 percent of singleton births,” she said. In addition, about one in
10 twins is born very low birthweight, putting them at risk for long-term
health problems and death, Martin said.

Upped risks also exist for mothers of twins, Martin said, and include a
higher odds for Cesarean delivery, gestational hypertension and diabetes,
she said.

About 90 percent of twins are born via C-section, Martin noted.

Will American women continue to see an increase in twin births? “The
pace of increase has declined somewhat in recent years,” Martin said, “but
it’s too soon to say whether that trend will continue.”

It’s possible that, due to changes in infertility treatments, the twin
birth rate may be slowing, Martin said. “As the baby boom generation ages
out and reproductive therapies become more refined that might lessen the
twin birth rat,” she said.

Multiple births in Western Europe and other countries during the 1980s
and 1990s have also increased, the authors note, and these are also
associated with maternal age and infertility therapies.

This report deals only with twins, but the growth in the number of
multiple births is even more “dramatic,” and the outcomes are even more
“problematic,” Martin said.

Dr. George Attia, an associate professor of OB-GYN and director of the
division of reproductive endocrinology and infertility at the University
of Miami School of Medicine, said technology is helping to reduce the
number of twin births.

“Twins and multiple births is one of the unwanted effects of fertility
treatment,” Attia said. “We are moving towards a single-embryo transfer to
reduce the risk of multiple pregnancy,” he said. “I am sure the rate will
keep falling as technology improves.”

Having fewer multiple births will also reduce the risks to infants and
mothers, Attia agreed.

More information

For more on U.S. birth rates, visit the U.S. Centers for
Disease Control and Prevention

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