Update contraceptive clinical data for obese women due to new research
Update contraceptive clinical data for obese women due to new research
Study shows OCs work equally well in obese, normal weight women
Review the next 10 patient charts in your inbox. If you note that at least one-third of the female patients are obese, you are not alone. An analysis of 2007-2008 data from the National Health and Nutrition Examination Survey shows that between 1988–1994 and 2007–2008, the prevalence of obesity among women age 20 and older increased from 22.9% to 33.0% among non-Hispanic white women, from 38.2% to 49.6% among non-Hispanic black women, and from 35.3% to 45.1% among Mexican-American women.1
Clinicians commonly use body mass index (BMI), defined as weight in kilograms divided by height in meters squared, to classify overweight (BMI 25.0–29.9), obesity (BMI greater than or equal to 30.0), and extreme obesity (BMI greater than or equal to 40.0).
The potential impact of weight on combined oral contraceptive (OC) effectiveness has been a topic of discussion at national conferences during the last decade since results of two retrospective studies suggested that heavier women may experience higher Pill failure rates than lighter women.2,3 However, results of a 2010 study that compared the effectiveness of the birth control pill in women with marked weight differences indicate the Pill works equally well in obese and normal weight women.4
Clinicians have long voiced concern about contraceptive efficacy for obese women who use combined pills, says Carolyn Westhoff, MD, professor of obstetrics and gynecology and director of the Division of Family Planning at Columbia University College of Physicians and Surgeons and an obstetrician/gynecologist at New York-Presbyterian Hospital/Columbia University Medical Center, both in New York City. With the results of the study in hand, that concern now can be laid to rest, says Westhoff, who served as lead author of the current study. "I think it is a great relief that in fact we found in our physiological study that the effect in the ovaries was the same, whether you were normal weight or obese," says Westhoff. "That is very reassuring that those women are going to get effective contraception."
Review study design
Researchers designed the current study as a prospective, double-blind, randomized trial of two 21-day monophasic pill formulations (20-mcg ethinyl estradiol [E2]/100-mcg levonorgestrel pill compared with a 30-mcg E2/150-mcg levonorgestrel pill) among normal-weight (body mass index 19.0-24.9) and obese (body mass index 30.0-39.9) women with regular menses and normal ovarian ultrasonography.
Women in the study underwent transvaginal ultrasonography and phlebotomy twice weekly for four weeks during the third or fourth pill cycle. Pill compliance was checked using serum levonorgestrel levels. Outcomes included follicular development, endogenous E2 levels, ovulation, and self-reported bleeding patterns.
A total of 226 women enrolled in the study, and 181 participants completed the study. Researchers retained 150 consistent pill users in the main analysis (96 normal weight, 54 obese).
Researchers found that consistent users of either pill dose had substantial suppression of follicular development; obesity and follicular development were not related. Among the consistent pill users, 2.7% ovulated during the study cycle (three of 96 normal weight and one of 54 obese participants). Two ovulations occurred with each pill formulation.
Inconsistent pill use or nonuse during the study cycle was associated with more ovulation (P<.001). Normal-weight and obese participants had similar follicular development, endogenous estradiol levels, Hoogland scores (a statistical tool used to assess ovarian suppression during Pill use), and bleeding patterns, researchers report.4
Consider dose, DVT risk
When the earlier research indicated possible higher risk for OC failure in obese women, many clinicians considered possible use of higher-dose pills to minimize failures. However, obese women are at higher risk for deep vein thrombosis (DVT), and using a higher-dose pill represents a higher risk for that complication, says Westhoff.
"We know heavier women are already at greater risk of DVT, and we know that a higher dose is a higher risk for DVT," she says. "I do not wish to add those two things together."
Obesity is indeed a risk factor for venous thromboembolism, said James Trussell, PhD, professor of economics and public affairs and director of the Office of Population Research at Princeton (NJ) University, during his presentation on contraception for obese women at the 2010 Contraceptive Technology conferences.5 Oral contraceptives further increase the effect of obesity on DVT, with a synergistic effect on OC use and BMI equal to or more than 25,6 said Trussell.
The U.S. Medical Eligibility Criteria for Contraceptive Use classes use of combined oral contraceptives (pill, patch, and ring) in women whose BMI is equal to or greater than 30 as a "2", where the advantages of using the method generally outweigh the theoretical or proven risks.7
Unplanned pregnancies are more dangerous for obese women, Trussell noted. The rate of complications during pregnancy and delivery increases with an increasing prepregnancy BMI in women,8 he said.
The intrauterine device (ParaGard Copper T 380A IUD, Duramed Pharmaceuticals, now Teva Women's Health, Woodcliff Lake, NJ, and the Mirena levonorgestrel intrauterine system, Bayer HealthCare Pharmaceuticals, Wayne, NJ) represents a "terrific choice" for obese women, noted Trussell. The ParaGard and Mirena devices decrease the risk of endometrial cancer, and the Mirena reduces menstrual blood loss, menorrhagia, and dysfunctional uterine bleeding, he observed.
Check daily pill taking
One finding from the current study reinforces an old adage for family planning clinicians: what matters most in Pill success is correct and consistent use. Of the 150 women who used the Pill consistently in the study, just three of the 96 women with normal weight ovulated, as did one of the 54 women who were obese. The researchers also noted that when women were not taking the Pill regularly, they ovulated with greater frequency.
"A key reminder is if you take your pill regularly, you are not going to ovulate," says Westhoff. "And if you are missing pills, you are going to ovulate."
Women who might have problems in taking daily pills should be counseled on other forms of contraception that are not dependent on such compliance, says Westhoff. "If you don't take the pills, they are not going to work, so we really need to make sure that daily pills are the right method for our patients," she advocates. "It doesn't matter if you are young or old, or male or female, many people have trouble taking daily pills."
References
- Ogden CL, Carroll MD. Prevalence of Overweight, Obesity, and Extreme Obesity Among Adults: United States, Trends 1976–1980 through 2007–2008. Accessed at www.cdc.gov/NCHS/data/hestat/obesity_adult_07_08/obesity_adult_07_08.pdf.
- Holt VL, Cushing-Haugen KL, Daling JR. Body weight and risk of oral contraceptive failure. Obstet Gynecol 2002; 99(5 Pt 1):820-827.
- Holt VL, Scholes D, Wicklund KG, et al. Body mass index, weight, and oral contraceptive failure risk. Obstet Gynecol 2005; 105:46-52.
- Westhoff CL, Torgal AH, Mayeda ER, et al. Ovarian suppression in normal-weight and obese women during oral contraceptive use: a randomized controlled trial. Obstet Gynecol 2010; 116(2 Pt 1):275-283.
- Trussell J. Contraception for obese women: an update. Presented at the 2010 Contraceptive Technology conferences. San Francisco and Boston; March and April 2010.
- Abdollahi M, Cushman M, Rosendaal FR. Obesity: risk of venous thrombosis and the interaction with coagulation factor levels and oral contraceptive use. Thromb Haemost 2003; 89:493-498.
- Centers for Disease Control and Prevention. US medical eligibility criteria for contraceptive use, 2010. MMWR Early Release 2010; 59:1-86.
- Rode L, Nilas L, Wøjdemann K, et al. Obesity-related complications in Danish single cephalic term pregnancies. Obstet Gynecol 2005; 105:537-542.
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