Women who used those methods were four times more
likely to wait more than 18 months between pregnancies compared to
those relying on condoms, researchers found.
The World Health Organization endorses a two-year period between
birth and a woman's next conception.
Still, one third of all repeat pregnancies in the U.S. occur within
18 months of the previous child's birth. And a growing body of
evidence shows this close timing increases the risk a baby will be
born early or at a low birth weight.
The time between pregnancies "cannot be explained only by the
mother's preferences," Heike Thiel de Bocanegra said.
She and her colleagues from the University of California, San
Francisco investigated the link between access to birth control or
family planning services and pregnancy spacing.
In the current study of 117,644 California women who'd had at least
two children, 64 percent waited 18 months or more between
pregnancies and the rest did not.
All women included in the study filed claims through the state's
Medicaid program for the poor, called Medi-Cal, or through health
providers offering state-funded family planning services.
The researchers matched data on claims for contraceptives to
California's birth registry.
"We assumed that access to contraception . . . would improve birth
spacing," Dr. Anitra Beasley wrote in an email to Reuters Health.
"This study actually examines this assumption," she said.
Beasley, who studies family planning at Baylor College of Medicine
in Houston, was not part of the current research.
Women who used long-acting reversible contraception, including IUDs
or implants, were four times more likely to wait at least 18 months
to conceive again, compared to those who only used "barrier"
contraceptives like condoms or spermicide.
More than half of women started using birth control pills, the ring
or the patch after giving birth. They were twice as likely to wait
at least 18 months between pregnancies as condom users.
Those relationships stood firm even when the researchers looked at
possible influences like the mother's race, education, age and
whether she was born in the U.S., according to the report published
in the American Journal of Obstetrics and Gynecology.
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Women in the study counseled by a certified family planning
service provider were 67 percent more likely to wait 18 months
between pregnancies, compared with women who utilized Medi-Cal
"Low-income women are sometimes seen only once after giving birth,"
Thiel de Bocanegra said.
"Some women receive contraception — some do not," she said.
Women in the study received four months worth of covered
contraceptives, on average. That number was dragged down by the one
third of women in the study who had no contraceptive claims at all.
For Meredith Matone, a researcher with PolicyLab at Children's
Hospital of Philadelphia, the study's large size helps build a
better understanding of how public health initiatives work in the
"The results we find in clinical trials do not always translate
well when implemented on a large scale, where they are subject to
challenges that include provider performance, patient compliance and
operational hurdles," Matone wrote in an email to Reuters Health.
"Under health care reform, there are opportunities to continue to
support such evidence-based public health programs for families,"
said Matone, who was not involved in the new research.
"Health care providers should know that the optimal pregnancy
interval is 18 months or more, and should encourage the use of
highly effective contraception during this period," Thiel de
"Pediatricians can help, too, by asking the mother what type of
contraception she is using," she said.
Journal of Obstetrics and Gynecology, online Dec. 16, 2013.
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