Having longer remove-by dates for contraceptives placed in the uterus would improve their convenience and bring down cost.
The researchers at the Washington University School of Medicine in St. Louis, MO, say that hormonal intrauterine devices (IUDs or "coils") and contraceptive implants (matchstick-sized, flexible plastic rods inserted into the arm) "remain highly effective one year beyond their approved duration of use."
The results are published online ahead of print in the Obstetrics & Gynecology journal, and come from an analysis of 500 of the intended 800 women to be enrolled in the study.
The recommended duration of use approved by the Food and Drug Administration (FDA) is:
- 3 years for contraceptive implants
- 5 years for hormonal IUDs.
But the implants in the study, Implanon and Nexplanon, and the IUD, Mirena, have all given reliable contraceptive performance in the study for a further year.
In this initial analysis, none of the 237 women continuing to rely on implants has become pregnant beyond the remove-by date.
There has been one pregnancy among the 263 women continuing to rely on hormonal IUDs, although this contraceptive success rate, say the researchers, is in keeping with that seen when there is compliance with the maximum recommended use for 5 years.
The study will continue to monitor the devices' contraceptive efficacy for up to 3 years beyond the recommended deadlines for their removal.
Co-author Dr. Colleen McNicholas, assistant professor of obstetrics and gynecology at the Washington University School of Medicine, outlines the potential implications of the research:
"This research is important because extended use of these devices will reduce cost to both the individual and insurer and improve convenience for women, who can delay removal and re-insertion."
When the women enrolled into the study they were all aged between 18 and 45 years. Informed of the risk of pregnancy by setting aside the FDA's advice, their contraceptives had to be within 6 months of expiry dates.
Other studies have also tested IUD and implant endurance beyond established limits - the researchers say earlier work by the World Health Organization and European researchers has shown that they may be effective for longer.
Senior author Dr. Jeffrey Peipert believes in the benefit to the population of such findings. The professor of obstetrics and gynecology at the medical school says:
"The longer a contraceptive method is effective, the bigger the impact it can have.
"In the long term, this work has the potential to change how we provide contraceptive methods around the world and can enable women to control their reproductive health and family size."
Increasing use of more reliable, reversible methods in the US
An at-a-glance chart on contraceptive effectiveness of various family planning options is available. Produced by the Centers for Disease Control and Prevention (CDC), it confirms the high level of reliability of reversible forms of birth control, with hormonal implants and IUDs sitting at the top of the diagram alongside sterilization, presenting a less than 1% chance of contraceptive failure.
CDC data on choice and take-up of family planning methods, collected from surveys conducted in 1995 and again in the years 2006-10, show that reversible methods such as hormonal IUDs have grown in popularity along with their wider availability and a corresponding drop in the use of other methods among committed couples, such as the pill and condoms.
Leading gynecologists in the US, however, from the American Congress of Obstetricians and Gynecologists (ACOG), say that, while there is an increasing use of the long-acting reversible contraceptive methods, implants and intrauterine devices are still receiving relatively low take-up in America.
"In part, high-unintended pregnancy rates in the US may be the result of relatively low use of long-acting reversible contraceptive methods, specifically the contraceptive implant and intrauterine devices."
The picture on the use of modern contraceptives is worse elsewhere, however. Earlier this week, medical scientists working for the World Health Organization reported that a low take-up of methods such as hormonal IUDs across 35 low-income to middle-income countries is responsible for 9 in 10 unwanted pregnancies.
Unreliable "traditional" methods were prevalent instead, such as having sex outside the most fertile part of the month. See: '15 million unwanted pregnancies' created by low contraception.