Lopez Laureen M, Grimes David A, Chen Mario, Otterness Conrad, Westhoff Carolyn, Edelman Alison, Helmerhorst Frans M
Clinical Sciences, FHI 360, Research Triangle Park, North Carolina, USA.
Cochrane Database Syst Rev. 2013 Apr 30(4):CD008452. doi: 10.1002/14651858.CD008452.pub3.
Obesity has reached epidemic proportions around the world. Effectiveness of hormonal contraceptives may be related to metabolic changes in obesity or greater body mass or body fat. Hormonal contraceptives mainly include oral contraceptives, injectables and implants, the transdermal patch, and the vaginal ring. We systematically reviewed the evidence on the effectiveness of hormonal contraceptives among overweight and obese women.
To examine the effectiveness of hormonal contraceptives in preventing unplanned pregnancies among women who are overweight or obese versus women of lower weight or body mass index (BMI).
Through January 2013, we searched MEDLINE, CENTRAL, POPLINE, ClinicalTrials.gov, and ICTRP. The previous search also included EMBASE. We contacted investigators to identify other trials.
All study designs were eligible. Any type of hormonal contraceptive could have been examined. Reports had to contain information on the specific contraceptive method(s). The primary outcome was pregnancy. Overweight or obese women must have been identified by an analysis cutoff for weight or BMI (kg/m(2)).
Data were abstracted by two authors. Life-table rates were included where available. For dichotomous variables, we computed an odds ratio with 95% confidence interval (CI). We used reported pregnancy rates or relative risk (RR) when those were the only results provided. The main comparisons were between overweight or obese women and women of lower weight or BMI. We assessed the quality of evidence for this review.
We found nine reports with data from 13 trials that included a total of 49,712 women. Five reports from 2002 to 2012 compared BMI groups; of those, one reported a higher pregnancy risk for overweight or obese women. In that trial, women assigned to an oral contraceptive containing norethindrone acetate 1.0 mg plus EE 20 µg and having a BMI at least 25 had greater pregnancy risk compared to those with BMI less than 25 (reported RR 2.49; 95% CI 1.01 to 6.13). The comparisons reported in the other four studies were not significantly different for pregnancy. These included studies of a combined oral contraceptive (COC), a transdermal patch, an implant, and an injectable. The COC study showed no trend by BMI or weight. With the transdermal patch, body weight was associated with pregnancy (reported P < 0.001) but BMI was not. The implant study had one pregnancy and the injectable study reported no pregnancies.Four studies from the 1990s used weight alone rather than BMI. Results were mixed. Studies of a vaginal ring (never marketed) and a six-rod implant showed higher pregnancy rates for women weighing at least 70 kg versus those weighing less than 70 kg (reported P values: 0.0013 and < 0.05, respectively). However, two implant studies showed no trend by body weight.
AUTHORS' CONCLUSIONS: The evidence did not generally show an association of BMI with effectiveness of hormonal contraceptives. However, the evidence was limited for any individual contraceptive method. Studies using BMI (rather than weight alone) can provide more information about whether body composition is related to contraceptive effectiveness. The efficacy of subdermal implants and injectable contraceptives may be unaffected by body mass. The contraceptive methods examined here are among the most effective when the recommended regimen is followed.The overall quality of evidence was low for this review. More recent reports provided moderate quality evidence, while the older studies provided evidence of low or very low quality for our purposes. Investigators should consider adjusting for potential confounding related to BMI. Trials should be designed to include sufficient numbers of overweight or obese women to adequately examine effectiveness and side effects of hormonal contraceptives within those groups.
肥胖在全球已达到流行程度。激素避孕法的有效性可能与肥胖、更高体重或体脂引起的代谢变化有关。激素避孕法主要包括口服避孕药、注射剂和植入剂、透皮贴剂及阴道环。我们系统回顾了超重和肥胖女性使用激素避孕法有效性的证据。
比较超重或肥胖女性与体重或体重指数（BMI）较低女性使用激素避孕法预防意外妊娠的有效性。
截至2013年1月，我们检索了MEDLINE、CENTRAL、POPLINE、ClinicalTrials.gov和ICTRP。之前的检索还包括EMBASE。我们联系了研究者以识别其他试验。
所有研究设计均符合要求。可以研究任何类型的激素避孕法。报告必须包含特定避孕方法的相关信息。主要结局为妊娠。超重或肥胖女性必须通过体重或BMI（kg/m²）的分析界值来确定。
由两位作者提取数据。如有可用的生命表率则纳入。对于二分变量，我们计算了95%置信区间（CI）的比值比。当仅提供报告的妊娠率或相对危险度（RR）时，我们使用这些数据。主要比较对象为超重或肥胖女性与体重或BMI较低的女性。我们评估了本综述的证据质量。
我们找到9篇报告，其数据来自13项试验，共纳入49712名女性。2002年至2012年的5篇报告比较了BMI组；其中1篇报告超重或肥胖女性妊娠风险更高。在该试验中，分配使用含1.0mg醋酸炔诺酮加20μg炔雌醇口服避孕药且BMI至少为25的女性，与BMI小于25的女性相比，妊娠风险更高（报告的RR为2.49；95%CI为1.01至6.13）。其他4项研究报告的妊娠情况比较无显著差异。这些研究包括复方口服避孕药（COC）、透皮贴剂、植入剂和注射剂的研究。COC研究未显示出BMI或体重的趋势。对于透皮贴剂，体重与妊娠有关（报告P<0.001），但BMI无关。植入剂研究中有1例妊娠，注射剂研究报告无妊娠。20世纪90年代的4项研究仅使用体重而非BMI。结果不一。阴道环（从未上市）和六棒植入剂的研究显示，体重至少70kg的女性与体重小于70kg的女性相比，妊娠率更高（报告的P值分别为0.0013和<0.05）。然而，两项植入剂研究未显示出体重趋势。
证据总体上未显示BMI与激素避孕法有效性之间存在关联。然而，对于任何一种单独的避孕方法，证据都很有限。使用BMI（而非仅体重）的研究可以提供更多关于身体组成是否与避孕有效性相关的信息。皮下植入剂和注射用避孕药的效果可能不受体重影响。遵循推荐方案时，这里所研究的避孕方法是最有效的方法之一。本综述的证据总体质量较低。近期报告提供了中等质量的证据，而较老的研究为本综述目的提供了低质量或极低质量的证据。研究者应考虑对与BMI相关的潜在混杂因素进行调整。试验设计应纳入足够数量的超重或肥胖女性，以充分研究这些组中激素避孕法的有效性和副作用。
