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Missing or improperly positioned intrauterine devices (IUDs) might have contributed to half of unintended pregnancies in a group of women who were using the devices, data from a small retrospective study suggests.

Among 42 IUD users, 36 devices were visible on sonography, and 21 of the 36 were incorrectly positioned, according to an article published online in the American Journal of Obstetrics & Gynecology.

In 31 women with intrauterine pregnancies, the IUD was in the endometrium in eight cases, malpositioned in 17, and not visible in six cases.

The findings suggest a need for routine sonography to confirm the positioning of IUDs.

"Gynecologists typically do a pelvic-and-speculum exam after placing an IUD, but there's no sonogram involved," Elysia Moschos, MD, of the University of Texas Southwestern Medical Center in Dallas, said in a statement.

"Based on the results of our study, we believe that sonographic evaluation of IUDs after insertion and for surveillance should be a topic of ongoing consideration."

Currently available IUDs have long-term pregnancy rates that vary from 0.5 to 1.9 per 100 women. When unintended pregnancy occurs in an IUD user, timely evaluation is necessary to reduce the risk of complications.

That evaluation typically includes transvaginal ultrasound to determine pregnancy location and to ascertain IUD location and retrievability, Moschos and co-author Diane M. Twickler, MD, also of UT Southwestern, wrote in their introduction.

Moschos and Twickler performed a retrospective chart review of first-trimester pregnancies among IUD users over a 12-month period. Their primary objective was to describe ultrasound findings, clinical characteristics, and pregnancy outcomes.

The review identified 42 women who became pregnant while using an IUD from July 1, 2007, through June 30, 2008. In all cases, sonography was performed by the UT Southwestern ob/gyn service, generating two- and three-dimensional images of the uterine cavities. Coronal reconstruction was by the Z-plane technique.

On the basis of sonographic results, the investigators defined pregnancy location as intrauterine, ectopic, or pregnancy of unknown location.

They defined IUD positioning as appropriate if both the arms and shaft were visualized within the fundal or midportion of the cavity. An IUD was considered malpositioned if any part extended into the lower uterine segment, myometrium, or endocervical canal.

For reference purposes, the authors used the 4,157 IUDs placed at UT Southwestern from July 1, 2008 to June 30, 2009.

Of the women who became pregnant while using an IUD, 36 (85%) were Hispanic, mean age was 26 (range 18 to 38), and mean duration of IUD use was 24.7 months (range two to 60 months). Gestational age at diagnosis and location of the IUD averaged eight weeks.

Sonography results showed that a majority of the 36 IUDs that could be visualized (58%) were malpositioned, and half of the entire study group had malpositioned devices (21 of 42).

Five patients were lost to follow-up, leaving 37 women with known pregnancy outcomes.

All eight women with pregnancies of unknown location had spontaneous abortions. Of three patients with ectopic pregnancy, two were treated with methotrexate and the third underwent laparoscopic salpingectomy for rupture.

The five patients lost to follow-up had intrauterine pregnancies, leaving 26 patients for evaluation.

Six of the 26 ended in fetal loss, three from first-trimester spontaneous abortion, one who had a spontaneous abortion after the IUD could not be removed, one from premature membrane rupture and subsequent spontaneous abortion, and one from fetal death at 20 weeks.

The authors reported that 31 of 42 women had symptoms, most commonly vaginal bleeding, pelvic pain, and missing IUD strings.

Symptoms did not predict IUD malpositioning, as only six of 14 patients with abnormal bleeding had incorrectly positioned devices as did two of five with missing strings.

However, nine of 12 women with pelvic pain did have IUDs that were out of place, as did all three patients with ectopic pregnancies.

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