WEDNESDAY, June 8 (HealthDay News) -- Women offered an intrauterine device (IUD) for birth control at the same time they're having a uterine aspiration due to miscarriage or abortion are much more likely to get one compared to women offered one later on, new research suggests.

The study also found that while the expulsion rate for IUDs inserted immediately after a uterine aspiration is higher than it is when women wait to get the device, this difference isn't statistically significant. In addition, the study found that complication rates were the same whether an IUD was immediately placed or inserted later.

"There were more expulsions in the immediate group. It was a little bit higher, but not exceptionally so," said study author Dr. Paula Bednarek, an assistant professor in the department of obstetrics and gynecology at Oregon Health and Science University in Portland, Ore.

"IUDs are a safe, extremely effective form of birth control. They're more effective than the pill, condoms and diaphragms at preventing pregnancy. But, IUDs are underutilized," she added.

Results of the study are published in the June 9 issue of the New England Journal of Medicine.

In the United States, more than half of unintended pregnancies are caused by the inconsistent or nonexistent use of birth control methods, according to background information in the study. Intrauterine devices are effective forms of birth control that don't require active use once they have been inserted, the study authors explained.

The study also pointed out that when birth control options are given to women just after an abortion, the risk of having a repeat abortion is reduced.

The use of IUDs fell out of favor decades ago when the devices were linked to an increased risk of pelvic inflammatory disease, said Dr. Mary Rosser, an obstetrician and gynecologist at Montefiore Medical Center in New York City. But that increased risk was due to the design of past devices, she added. An IUD is T-shaped, and has a string or tail that hangs out of the cervix that aids in the removal of the device. Older devices had strings that were braided or contained numerous strings twisted together.

That design, explained Rosser, seemed to allow for the growth of bacteria, which then contributed to pelvic inflammatory disease. "Those tails were acting like wicks," she said.

Newer IUDs have better designs, and haven't been associated with an increased risk of pelvic inflammatory disease, she noted.

For the current study, the researchers recruited 575 adult women at four sites across the United States. All of the women were undergoing uterine aspiration (sometimes referred to as D and C) due to miscarriages or planned abortion. All of the women in the study expressed an interest in getting an IUD.

The women were randomly selected to receive the IUD just after the uterine aspiration (immediate placement) or were scheduled to have the IUD inserted at their follow-up appointment two to six weeks later (delayed placement).

All of the women in the immediate group had an IUD inserted, while just 71.3 percent of those in the delayed group ended up getting an IUD, according to the study. No pregnancies occurred in the immediate placement group, while five of the women in the delayed group who had never gotten the IUD became pregnant.

After six months, 5 percent of the women in the immediate placement group had experienced an IUD expulsion, while 2.7 percent of the delayed insertion group did. Rates of complications didn't differ between the groups, the researchers noted.

Bednarek said that most of the women in the delayed group who ended up not getting an IUD hadn't changed their minds about wanting an IUD, but instead cited logistical reasons, such as transportation or not being able to get time off work or find child care as the reasons they didn't make their appointment.

Rosser also noted that guilt or privacy issues may play a role for some women, particularly if they've been treated at a clinic where there were anti-abortion protestors. "There's a sense of women wanting to put that bad experience behind them, and you often don't get women returning for follow-ups," she said.

In the current study, 150 women didn't complete the six-month trial.

Both experts agreed that IUDs are an effective form of birth control that is currently underutilized.

More information

To learn more about IUDs, visit the American Congress of Obstetricians and Gynecologists.