Intrauterine contraceptive devices (IUDs) are the most popular form of reversible contraception worldwide, comprising 23 percent of female birth control use. But there’s a failure rate of between 0.2 and 0.8 percent depending on the type of IUD used.

For those women who do get pregnant while using an IUD, new research from Israel reveals some disturbing news.

The researchers compared the outcomes of 221,800 deliveries from 1991 to 2014. Nearly 1% of the new mothers had an IUD that was removed early in the pregnancy and 6% retained their IUD throughout gestation.

Women who conceived while using an IUD had a greater chance of preterm delivery (14.3% for those women who removed their IUD and 14.1% for those who retained their IUD throughout the pregnancy vs. 6.8% for women who did not conceive while using an IUD).

IUD users also had a greater rate of chorioamnionitis infection (2.7-5% for IUD users compared with 0.6% for women without an IUD); lower birth weight (11.3-12.1% of IUD-using women delivered babies under five pounds vs. 6.6% for those who didn’t use an IUD); and higher perinatal mortality (1.3-2% of women who used an IUD lost the fetus vs. 0.5% for women who did not use an IUD when they became pregnant).

The research from Ben-Gurion University of the Negev and Soroka University Medical Center, both in Beersheva, was presented last week at the Society for Maternal-Fetal Medicine’s 38th annual Pregnancy Meeting  and is the “first report tracking children born to mothers using an IUD over a long timeframe,” said Dr. Gali Pariente, a faculty member of the BGU Division of Obstetrics and Gynecology.

“Working with a large sample over 23 years allowed us to investigate obstetric parameters that hadn’t been examined previously in large groups.”

Others working on the study included Dr. Tamar Wainstock of BGU’s School of Public Health, and Prof. Eyal Sheiner, vice dean for student affairs of the BGU Faculty of Health Sciences and head of obstetrics at Soroka.

When an IUD is inserted, the uterus recognizes it as a foreign body and produces an inflammatory reaction that impairs sperm implantation. Adding copper or progesterone enhances this response. The risk of IUD failure is highest within the first year of insertion.

The results of the study indicate that “careful monitoring of any women who conceive while using an IUD” is recommended, Pariente stressed.