Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Getting pregnant while on the pill: Yet another health hazard of being overweight

30.12.2004


Overweight and obese women who take oral contraceptives are 60 percent to 70 percent more likely to get pregnant while on the birth-control pill, respectively, than women of lower weight, according to new findings from Fred Hutchinson Cancer Research Center that will be published in the January issue of Obstetrics & Gynecology.



The study, led by epidemiologist Victoria Holt, Ph.D., M.P.H., a member of Fred Hutchinson’s Public Health Sciences Division, is the largest case-control study of its kind to examine the link between body-mass index and oral-contraceptive failure. The research was conducted in collaboration with Delia Scholes, Ph.D., a senior investigator at the Center for Health Studies at Group Health Cooperative in Seattle.

"The results of our study represent yet another reason why obesity is a health hazard," Holt said. "Overweight and obese women have a significantly higher risk of getting pregnant while on the pill than women of normal weight, and this translates into a substantial number of unplanned pregnancies." Among 100 women taking oral contraceptives for a year, Holt’s study suggests that an additional two to four women will get pregnant due to being overweight or obese. "This higher risk of pregnancy also translates into a higher number of obesity-related complications of pregnancy, which range from gestational diabetes and high blood pressure to Cesarean delivery," Holt said.


Body-mass index, or BMI, is a measure of body fat based on height and weight. The World Health Organization divides BMI into four categories for both men and women: underweight (18.5 or lower), normal (18.5 to 24.9), overweight (25 to 29.9) and obese (30 or greater). A BMI calculator is available on the National Institutes of Health Web site at http://nhlbisupport.com/bmi/bmicalc.htm "We found little difference or variation in the risk of contraceptive failure among women who fell into the first three quartiles of body-mass index, but the risk jumped up dramatically among women in the fourth quartile," said Holt, also a professor of epidemiology at the University of Washington School of Public Health and Community Medicine.

Holt and colleagues found the association between extra pounds and pill failure first surfaced among overweight women whose body-mass index was 27.3 or higher, which is equivalent to a 5-foot, 4-inch woman who weighs 160 pounds or more. These women faced a 60 percent greater risk of getting pregnant while on the pill. Those considered obese, with a BMI of 32.2 or greater, faced a 70 percent greater risk.

While no one knows for sure why overweight and obese women experience a higher degree of oral-contraceptive failure than their thinner counterparts, several biological mechanisms could account for the effect.

One possible explanation is increased metabolism. "The more a person weighs, the higher their basal metabolic rate, which can shorten the duration of a medication’s effectiveness," she said. Another possibility is that the heavier a person is, the more liver enzymes they have to clear medications from the body, causing a drop in circulating blood levels of the drug. A third theory is based on the fact that the active ingredients in oral contraceptives – the hormones estrogen and progesterone – are stored in body fat. "The more fat a person has, the more likely the drug is sequestered, or trapped, in the fat instead of circulating in the bloodstream," Holt said.

Another factor that may account for obesity-related pill failure is that today’s oral contraceptives contain relatively low hormone levels compared to those first introduced four decades ago. "Hormone levels have decreased fivefold in an effort to reduce unwanted side effects ranging from weight gain to risk of blood clots and stroke," Holt said. "Today’s pill dose is high enough for most women but may not be adequate for all."

So does this mean that overweight women who don’t want to risk an unplanned pregnancy should demand a higher-dose pill? Not necessarily, Holt said. "Overweight women are more likely to have cardiovascular-disease risk factors than normal-weight women, and to increase the dose of contraceptive hormones might increase cardiovascular risks even more," she said.

Instead, Holt recommends that overweight women who have completed childbearing consider a permanent form of birth control such as sterilization, and that overweight women who have not yet completed childbearing consider using a backup form of birth control while on the pill, such the condom or other barrier methods.

Another recommendation for heavy women on the pill is to lose weight, although this study did not specifically examine the impact of weight loss on the pill’s effectiveness. "I think losing weight, if one is substantially overweight, is a terrific idea for many health reasons and a laudable goal," Holt said. "I also acknowledge that it is often difficult to do."

For the study, Holt and colleagues compared weight and body-mass index of 248 women who became pregnant while on the pill to an age-matched comparison group of 533 nonpregnant oral-contraceptive users. All of the study participants were enrolled in Group Health Cooperative, a Seattle health-maintenance organization. The women’s self-reported history of weight, pregnancy and oral-contraceptive use was verified through medical, laboratory and pharmacy records, which added statistical strength to the study’s findings, Holt said.

Kristen Woodward | EurekAlert!
Further information:
http://www.fhcrc.org

More articles from Studies and Analyses:

nachricht Do microplastics harbour additional risks by colonization with harmful bacteria?
05.04.2018 | Leibniz-Institut für Ostseeforschung Warnemünde

nachricht Rutgers-led innovation could spur faster, cheaper, nano-based manufacturing
14.02.2018 | Rutgers University

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>