Contraceptive options for your obese patients

March 1, 2007

The possibility that contraceptives are more likely to fail in obese patients is only one reason why you need to take a different tack when counseling them about their most appropriate birth control options. . .

The possibility that contraceptives are more likely to fail in obese patients is only one reason why you need to take a different tack when counseling them about their most appropriate birth control options. . .

. . . You need to advise them, too, that combination oral contraceptives (COCs) may put overweight or obese women at increased risk for both arterial and venous thromboembolic disease-as may certain other birth control methods. These concerns, combined with the ever-growing obesity epidemic among reproductive-aged American women, make it imperative for us to focus family planning efforts on our overweight patients.

The statistics speak volumes. The number of overweight and obese Americans has soared over the last few decades. Some 66% of adults in the United States are overweight or obese, defined as a body mass index (BMI) of 25.0 to 29.9 kg/m2 and 30.0 kg/m2 or more, respectively, according to a recent national survey.1 The epidemic continues to worsen, with the figures for both overweight and obese adults up 10 percentage points in the last 20 years. Given the increased pregnancy-related morbidity in these women and the fact that nearly half of all pregnancies in the US are unintended, it's crucial that we help our overweight patients select the most appropriate birth control method.

Obese women are at higher risk of unintended pregnancy than their non-obese counterparts. Data from a study of more than 24,000 women, which examined the intendedness of pregnancy, contraceptive use, body weight, and BMI at the time of conception, suggested that overweight and obese women using contraception were more likely than non-obese women to unintentionally get pregnant.2 This difference wasn't seen in women who weren't using birth control at the time they conceived. These findings suggest that the overall effectiveness of contraceptives is decreased in overweight and obese women.

COMBINED ORAL CONTRACEPTIVES

As you know, estrogen and progesterone-containing oral contraceptive methods have a reported effectiveness of 92%, meaning that eight out of 100 women will conceive a pregnancy in a single year of typical or "real world" use.3 Evidence suggests overweight and obese women are at greater risk of unintended pregnancy while using COCs than are lean women (Table 1). In a case–control study, researchers found an increased risk of unintended pregnancy in women whose BMIs were greater than 27.3 kg/m2 when compared to women with a BMI of 27.3 kg/m2 or less.4 This effect was even more pronounced when investigators zeroed in on data for just the consistent COC users, concluding that the decreased effectiveness in this population would result in an additional two to four pregnancies per 100 women years. Data also suggest that in overweight and obese women, very low-dose COCs may be even less effective than low-dose pills.5 We don't know what causes this decreased efficacy; but research suggests increased metabolism or disproportionate sequestration of hormonal contraception in adipose tissue.6

Women using COCs that contain less than 50 μg of daily estrogen have a risk of venous thromboembolic disease (VTE) that's four times the risk of non-users.7 And while the absolute number of women using COCs who suffer from VTE is small, this risk is likely increased for overweight and obese women. In the World Health Organization Collaborative Study of Cardiovascular Disease and Steroid Hormone Contraception, researchers identified a BMI of 25 or greater as an independent risk factor for VTE in COC users.8 The same holds true for arterial thromboembolic disease. Another sobering statistic: the risk of acute myocardial infarction (AMI) and stroke in COCs users-which is associated almost exclusively with female smokers over age 35 with preexisting cardiovascular disease such as hypertension-is five times higher than in non-COC users. However, obesity is also a risk factor for arterial thromboembolic events in COC users, associated with twice the risk of AMI and stroke of non-obese COC users.9 Consideration of these risks should be balanced with the six- to tenfold increased probability of VTE and the rare but likely increased risk of AMI and stroke in pregnancy.10 Finally, despite widespread concern that COCs cause weight gain, there's no evidence to support this claim.11 If one of your overweight or obese patients is actively working to lose weight, don't let fear of weight gain on COCs impact prescribing decisions.

THE CONTRACEPTIVE PATCH AND VAGINAL RING

Pooled data from three multicenter trials point to an overall failure rate of the contraceptive patch (ethinyl estradiol 20 μg and norelgestromin 150 μg daily) of 0.8%.12 Of the 15 pregnancies observed overall, 33% occurred in the less than 3% of women who weighed 198 lb (90 kg) or more. The remaining 67% of pregnancies were equally distributed among the subjects of the different weight categories under 198 lb. Unfortunately, data on the contraceptive ring (ethinyl estradiol 15 μg and etonogestrel 120 μg daily) in overweight and obese women are not available. As with COCs, temper any prescribing caveats with the importance of avoiding unintended pregnancy in this high-risk group.

PROGESTERONE-ONLY PILLS AND INJECTIONS

Progesterone-only methods include progesterone-only pills (POPs), depot medroxypro-gesterone acetate (DMPA), and the newer subcutaneous DMPA, depo-subQ Provera 104. From a safety standpoint, progesterone-only methods provide a viable contraceptive alternative for patients with contraindications to estrogen. Given the increased risk of vascular complications in overweight and obese patients using combined contraceptive methods, these women's preferred option might be a progesterone-only method.

No studies have specifically examined POPs in overweight and obese women. A small study of obese and non-obese DMPA users (mean BMI 32.2 kg/m2 and 17.9 kg/m2, respectively), however, showed no difference between weekly serum concentrations of steroid hormone over 12 weeks following the initial injection.13 With unchanged serum concentration, contraceptive efficacy should remain unchanged, as well. No pregnancies were observed in another study that examined the contraceptive efficacy of depo subQ Provera 104, in which nearly half (44%) of the patients were either overweight or obese.14

The bad news is that women often discontinue DMPA due to menstrual irregularity, a common side effect with this method. But the better news is that increased BMI may actually be linked with less uterine bleeding with DMPA, which could encourage larger women to stay the course.15 Another downside, though, is the evidence linking DMPA with increased weight gain by women who were overweight or obese to begin with (vs. lean women using DMPA), an association that may be particularly marked in younger women.16 A retrospective study of 239 adolescents using DMPA versus OCs for 1 year found that nonobese DMPA users gained an average of almost 7 lb versus 13.6 lb in obese DMPA users.17

THE INTRAUTERINE DEVICE

The intrauterine device provides long-term, reversible contraception with few side effects. The Copper T380A and the levonorgestrel IUS are increasingly popular in the US-a popularity that will likely continue to grow as product labeling is updated to reflect scientific evidence. A recent labeling change in the Copper T380A widens eligibility criteria to include women with a history of STDs and pelvic inflammatory disease, but who are no longer at high risk for genital infection.18 Once again, no studies have examined IUD use exclusively in overweight and obese women, but there's no biologically plausible reason to anticipate decreased safety or efficacy in heavier women. It's likely that both types of IUDs provide a low-risk, long-term, reversible method without the increased risk of vascular events associated with estrogen, the weight gain with DMPA, and the higher risk of complications encountered with surgical sterilization.

Before placing IUDs in larger women, though, be prepared for increased difficulty in determining uterine size and position; you may also find it difficult to visualize the cervix for insertion and removal.19 Proper equipment such as a larger specula and ultrasound guidance can assist with insertion in women who are overweight and obese. There's no evidence that the copper-releasing or levonorgestrel IUD causes women to gain weight, making this an ideal method for overweight women in whom additional weight gain will heighten the risk of obesity-related comorbidities.20,21

THE CONTRACEPTIVE IMPLANT

Implanon, a single-rod etonogestrel-releasing contraceptive implant, provides 3 years of reversible contraception when inserted into the subcutaneous tissue of the upper arm. After having been used by more than 2.5 million women internationally, this device was recently approved by the FDA. Despite its large-scale use worldwide, no published data exist that would indicate a difference in the efficacy rate or safety profile in overweight and obese women. Trends in the data suggest that serum etonogestrel levels are lower in heavier women.22 We just don't know whether this decrease in bioavailable hormone levels translates into lower contraceptive effectiveness. Therefore, while awaiting these studies, be cautious in counseling overweight and obese patients, and advise them that this method could turn out to have higher failure rates than expected. That said, however, weighing the risks and benefits of long-term reversible contraceptives for the appropriate candidate does not currently preclude the contraceptive implant.

BARRIER METHODS AND EMERGENCY CONTRACEPTION

There's no reason to believe that barrier methods, such as the female and male condoms, the diaphragm, and the cervical cap, are less effective or cause more side effects in the overweight patient. When counseling these patients, as with all patients, highlight the lower contraceptive effectiveness of barrier methods when compared with hormonal options and the copper-releasing IUD.

When barrier methods fail, or when patients fail to use them, they can turn to emergency contraception (EC), which significantly reduces the risk of unintended pregnancy. The most effective form of EC is insertion of the copper-releasing IUD within 1 week of unprotected intercourse, which is suitable for overweight and obese women. But it's not the most popular form. More commonly used is the progesterone-only method of EC, levonorgestrel, marketed as Plan B. The medicine works by delaying ovulation and decreasing the chance of conception after unprotected intercourse. Because there's no evidence to suggest that the pharmacokinetics of levonorgestrel are altered based on body habitus alone, don't discourage overweight and obese patients from using EC based solely on BMI.

PERMANENT STERILIZATION

Female sterilization is particularly challenging-given its potentially serious complications in overweight and obese women. The Collaborative Review of Sterilization reported the overall complication rate of 0.9 per 100 procedures for interval tubal sterilization and defined major complications as unscheduled major surgery, transfusion, febrile morbidity, life-threatening event, rehospitalization, and death.23 The researchers found obesity to be one of four preoperative factors that seemed to increase the probability of major complications; diabetes, general anesthesia, and previous abdominal or pelvic surgery were the other three. Obese women were 70% more likely to have a major complication associated with interval sterilization than non-obese women. While the overall rate of complications is relatively small and the increase for obese women is modest, larger women should still be counseled regarding the risk of intraoperative and postoperative complications related to increased BMI. These risks must be balanced with the benefit of permanent sterilization in individual patients, factoring in the hazards of pregnancy and gestational comorbidities that are increased for obese women.

Hysteroscopic tubal occlusion (Essure) provides an alternative to interval laparoscopic and postpartum tubal ligation for patients desiring permanent contraception. Be sure to perform the procedure during the follicular phase of the menstrual cycle to ensure that the endometrial lining will be thin and the tubal ostia visible. An additional aid to improving visualization is to treat the patient preoperatively with hormonal contraceptives that suppress the growth of the uterine lining, such as DMPA. However, surgery shouldn't begin immediately after you initiate hormonal contraception because endometrial suppression doesn't take effect immediately. Preoperative endometrial preparation can be especially important in overweight and obese women who are more likely to have thickened endometrium due to their increased adiposity. Afterwards, patients are required to continue using an alternative method of contraception for 3 months prior to confirmation of tubal occlusion via hysterosalpingogram. Despite these constraints, hysteroscopic tubal occlusion can be the preferred sterilization option for women who are obese or who've had previous abdominal or pelvic surgery. Finally, don't overlook male sterilization, which offers an additional alternative for couples interested in permanent contraception and is sometimes preferable for women with coexisting medical complications, such as obesity, that increase the risks of surgery.

Like any preventive therapy in medicine, the decision to use a method of birth control is based upon a careful evaluation of risks and benefits. Unfortunately, data on the safety and efficacy of several contraceptive methods in overweight women are not available. We do know, however, that COCs and the transdermal patch are less effective and that COCs increase the risks of both arterial and venous thromboembolic disease in overweight women. The progesterone-only injectable method, DMPA, appears to have an added risk of significant weight gain, which may preclude its use in some patients or mandate additional nutritional counseling. The option of laparoscopic sterilization carries the increased risk of perioperative complications for overweight and obese women. With that in mind, perhaps the best advice you can give overweight or obese patients is that IUDs, hysteroscopic tubal occlusion, and vasectomy may provide safer, long-term contraceptive alternatives.

DR. COWETT is Director, Center for Reproductive Health, Assistant Director, Fellowship in Family Planning, and Assistant Clinical Professor, Obstetrics and Gynecology, University of Illinois at Chicago, Chicago, Ill.

REFERENCES

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