HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Holt, V. L. Articles by Daling, J. R. Search for Related Content PubMed PubMed Citation Articles by Holt, V. L. Articles by Daling, J. R. Related Collections Contraception Epidemiology/public health General gynecology

Body Mass Index, Weight, and Oral Contraceptive Failure Risk

Victoria L. Holt, PhD, MPH^*, Delia Scholes, PhD^*, Kristine G. Wicklund, PhD, Kara L. Cushing-Haugen, MS and Janet R. Daling, PhD^*

From the Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, Washington; Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington; and Center for Health Studies, Group Health Cooperative, Seattle, Washington.

Address reprint requests to: Victoria L. Holt, PhD, MPH, Fred Hutchinson Cancer Research Center, Division of Public Health Sciences (M4 B874), 1100 Fairview Avenue North, PO Box 19024, Seattle, WA 98109; e-mail: vholt{at}u.washington.edu.

	ABSTRACT

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
OBJECTIVE: This project was supported by grant 1 R01 HD-34712 from the U.S. National Institute of Child Health and Human Development.

To estimate the effect of body mass index (BMI) and weight on risk of pregnancy while using oral contraceptives (OCs).

METHODS: We conducted a case-control study of 248 health maintenance organization enrollees who became pregnant while using OCs between 1998 and 2001 and 533 age-matched enrollees who were nonpregnant OC users during the same period. Using logistic regression we calculated adjusted odds ratios (ORs) to estimate the risk of pregnancy according to BMI and weight quartile.

RESULTS: Among all OC users, when compared with women having a BMI of 27.3 or less, the risk of pregnancy was nearly 60% higher in women with BMI greater than 27.3 (OR 1.58, 95% confidence interval [CI] 1.11–2.24) and over 70% higher in women with BMI greater than 32.2 (OR 1.72, 95% CI 1.04–2.82). Among consistent users (women who missed no pills in reference month), the risk of pregnancy was more than doubled in women with BMI greater than 27.3 (OR 2.17, 95% CI 1.38–3.41) or BMI greater than 32.2 (OR 2.22, 95% CI 1.18–4.20). When compared with women weighing 74.8 kg or less, among consistent OC users the risk of pregnancy was over 70% higher in women weighing more than 74.8 kg (OR 1.71, 95% CI 1.08–2.71) and nearly doubled in women weighing more than 86.2 kg (OR 1.95, 95% CI 1.06–3.67).

CONCLUSION: Our results suggest that being overweight may increase the risk of becoming pregnant while using OCs. If causal, this association translates to an additional 2–4 pregnancies per 100 woman-years of use among overweight women, for whom consideration of additional or effective alternative contraceptive methods may be warranted.

LEVEL OF EVIDENCE: II-2

	MATERIALS AND METHODS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The subjects in this population-based, case-control study were drawn from English-speaking female enrollees of Group Health Cooperative, who were 18 years of age or older. Group Health Cooperative is a large, mixed-model, consumer-owned health maintenance organization in Washington State. Women with a positive pregnancy test at Group Health Cooperative between March 1, 1998, and February 28, 2001, who had filled an OC prescription at the cooperative within the previous 3 months (n = 756) were identified and contacted by study personnel; 546 of these women agreed to participate in the study (72.2%). Medical record review and further queries of these potential cases determined the date of their last menstrual period before conception, and we excluded as OC nonusers the 257 women who reported that they did not use OCs after this menstrual period. Additionally, 9 women could not be recontacted, leaving 280 participating cases. We assigned all cases a reference month, which was the month during which they conceived. Potential controls were sampled from the Group Health Cooperative pharmacy records of enrollees who filled at least one OC prescription at the cooperative between March 1, 1998, and February 28, 2001, and who did not have a positive pregnancy test. Control sampling was random within 5-year age groups, with the number selected in each age group based on the number of cases in that age group. When contacted, 701 of the 945 potential control women (74.2%) agreed to participate. Further queries of potential controls determined that, during the reference month (a month randomly assigned to controls to correspond to cases’ reference months), 156 women either did not have intercourse with a male partner or did not use OCs for contraception; these women were excluded. Additionally, 9 women could not be recontacted, leaving 536 participating controls. The Institutional Review Boards at Fred Hutchinson Cancer Research Center and Group Health Cooperative approved the study protocols. All participants gave written informed consent and were offered $20 to partially compensate them for their time.

For the analyses presented here, we excluded one case who declined to provide her weight. Additionally, we excluded the 31 cases and 3 controls who missed 5 or more days of OCs in the reference month, because this pattern of use may indicate that they were not truly using OCs for contraception that month. A total of 248 cases and 533 controls remained for analysis.

Female study personnel interviewed participants by using a structured questionnaire that elicited a lifetime history of a variety of demographic, reproductive, medical, and lifestyle factors up to the reference month. Mean time from reference month to interview was 7.1 months (standard deviation [SD] 3.81) for cases and 7.9 months (SD 3.14) for controls. At the in-person interview, we verified with each case her conception date with the aid of an individualized calendar documenting her last menstrual period before pregnancy and date of her positive pregnancy test. Similarly, we used the individualized calendars to confirm with controls at interview their nonpregnancy status in the reference month. We relied on a combination of pharmacy and interview data to determine participants’ reference-month OC use, and we confirmed with all subjects at the in-person interview that their use of OCs was for contraceptive purposes. We ascertained use details (dates started and stopped, pill-taking patterns, brand and dose of OCs used) from participant self-report and from color photographs of OC pills and packets and individualized reference-month calendars to aid recall. We asked participants to tell us whether they had taken the OCs they obtained from Group Health Cooperative pharmacies and whether they had taken OCs obtained elsewhere. We verified participants’ reports of reference-month OC brand and dose by linkage with Group Health Cooperative pharmacy records available for all study participants. On the basis of pharmacy data, we specified reference month OC brand and dose for 28 cases and 29 controls who did not know their reference-month brand and/or dose and reclassified reference-month brand and dose for 34 cases and 36 controls whose Group Health Cooperative pharmacy brand and dose data differed from self-report and who stated that they had not obtained OCs outside of Group Health Cooperative.

Reference-month body weight was ascertained from each participant's self-report at interview. We compared self-reported weights with medical record weights, which were available for 98.3% of participants. These weights, which were recorded a median of 22 weeks before the reference month, were on average 2 kg higher than self-reported weights (2.0 kg for cases, 1.9 kg for controls); 80.2% of nonpregnant weights recorded in the medical record within the 12 months before reference month were within 5 kg of self-reported reference-month weight. Participants’ standing heights were obtained by measurement at interview.

We calculated the OC-associated pregnancy rate as the number of laboratory-confirmed pregnancies during the study period among Group Health Cooperative enrollees who were using OCs at the time of conception, divided by the number of woman-years of OC use for contraception among Group Health Cooperative enrollees during the study period. The number of pregnancies that occurred while using OCs was determined by applying the percentage eligible (52.1%) among our potential cases who agreed to participate to the total number of women we identified as potential cases (n = 756), yielding an estimated 394 OC-associated pregnancies. Based on the Group Health Cooperative pharmacy data on OC pill packs prescribed and the proportion of potential controls whose reference month OC use was for contraceptive purposes, we estimated that approximately 14,317 woman-years of OC use for contraception occurred among Group Health Cooperative enrollees during the study period.

We used unconditional logistic regression in STATA 6.0 (STATA Corporation, College Station, TX) statistical software to compute odds ratios (ORs) and 95% confidence intervals (CIs) for the associations of 1) BMI (kg/m²) and 2) body weight (kg) with pregnancy while using OCs. Because our previous research indicated that there may be a threshold effect, to investigate this possibility and to determine the location of such a threshold, we initially categorized BMI and weight by quartile using the control population's distribution. Two quartile-based comparisons were made: each higher quartile versus the lowest quartile and the highest quartile versus all other quartiles combined. For the BMI analyses, the highest quartile (BMI > 27.3) corresponded closely to the definition of overweight (BMI 27.3) used in Healthy People 2000,¹² based on the 85th percentile of 20–29-year-old women in the U.S. National Health and Nutrition Examination Survey II.¹³ To determine whether an additional threshold existed at higher levels, such as those reported for the transdermal contraceptive patch, in additional analyses the highest quartile was further split in two. For BMI, the split was based on the National Health and Nutrition Examination Survey II definition of severely overweight (BMI > 32.2, the 95th percentile of 20–29-year-old women); severely overweight women were compared with women who were not overweight (BMI 27.3). For weight, the top quartile was split in half per the control population, and the heaviest women (>86.2 kg) were compared with those in the bottom 3 weight quartiles combined ( 74.8 kg).

Factors examined as potential confounders included race, marital status, education, income, smoking history, pregnancy and birth history, desire for future children, intercourse frequency, OC type/dose and OC pill-taking behavior in reference month, concurrent use of other contraception in reference month, concurrent illnesses (Crohn's disease, colitis, liver disease, diabetes mellitus, seizure disorder, tuberculosis) and medications (antibiotics, vitamin C) in reference month, and time from reference date to interview date. We classified OC type/dose as follows: 1) less than 35 µg ethinyl estradiol (E2) monophasic, 2) 35 µg ethinyl E2 monophasic, 3) multiphasic, and 4) progestin-only. Factors used in frequency matching (age, reference year) or those that altered the estimates by 10% or more were included in the final logistic models.¹⁴ Age (categorized in 5-year groups), reference year (categorized as a continuous variable), and parity (categorized as 0, 1, 2 births) met these criteria. We tested for the interaction of BMI and weight with OC type/dose, OC pill-taking behavior, and parity with the likelihood ratio test; no significant (P < .05) interaction was noted.

The main analyses used all OC users who missed less than 5 days of pills in reference month. Subanalyses were conducted using only consistent users, defined as those who missed no OCs in the reference month.

	RESULTS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
We found an OC-associated pregnancy rate of 2.8 per 100 woman-years of OC use among Group Health Cooperative enrollees during the study period. Study participants who became pregnant while using OCs differed from those who did not in several demographic and behavioral characteristics (Table 1). Cases were more likely than controls to be black, married or living as married with their partners, and current smokers; and they had lower educational attainment and family income. Additionally, cases were more likely than controls to have had one or more prior confirmed pregnancies, live births, spontaneous abortions, and induced abortions. Cases were 5 times as likely as controls to have become pregnant in the past while using oral contraceptives, and (before their reference-month pregnancy) they were less likely than controls to express a desire for future children.

Mean BMI among cases was 26.3 (range 16.8–51.3) and among controls was 24.9 (range 16.7–63.5). In logistic models controlling for age, reference year, and parity, we found little difference in risk of OC failure among women in the first 3 quartiles of BMI. However, the risk of pregnancy was over 60% higher in women in the highest BMI quartile (BMI > 27.3, OR 1.62, 95% CI 1.02–2.57) than in women in the lowest (referent) BMI quartile (Table 2). Subsequent analyses grouping the lowest 3 BMI quartiles together as the reference group (BMI 27.3) found an increase in pregnancy risk of nearly 60% for women in the highest BMI quartile (BMI > 27.3, OR 1.58, 95% CI 1.11–2.24) and an over 70% increase in risk for women in the highest end of the highest quartile (BMI > 32.2, OR 1.72, 95% CI 1.04–2.82). Analyses limited to consistent users (women who stated they missed no pills in the reference month) revealed stronger associations: the risk of pregnancy was more than doubled in women with BMI greater than 27.3 compared with women in the lowest 3 BMI quartiles combined (OR 2.17, 95% CI 1.38–3.41). This increase in risk did not change appreciably with further increases in BMI (BMI > 32.2, OR 2.22, 95% CI 1.18–4.20).

Mean weight among cases was 71.1 kg (range 46.3–136.1) and among controls was 67.5 kg (range 41.3–190.5). In logistic models controlling for age, reference year, and parity, the OR among women in the highest quartile (> 74.8 kg) was 1.33 (95% CI 0.84–2.11) compared with those in the lowest quartile ( 56.7 kg), and 1.36 (95% CI 0.95–1.95) compared with the lowest 3 quartiles combined (Table 3). Risk was highest for women in the top half of the highest weight quartile: women weighing more than 86.2 kg had an OR of 1.62 (95% CI 0.99–2.64) compared with those weighing 74.8 kg or less. Risks were higher and statistically significant among participants who missed no pills in the reference month: compared with women weighing 74.8 kg or less, the risk of pregnancy was over 70% higher in consistent users weighing more than 74.8 kg (OR 1.71, 95% CI 1.08–2.71) and nearly doubled in consistent users weighing more than 86.2 kg (OR 1.95, 95% CI 1.06–3.67).

	DISCUSSION

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
In this study the risk of becoming pregnant while using OCs was significantly elevated among women in the highest BMI quartile, compared with women of lower BMI. Our analyses revealed an apparent threshold effect: there was no graded increase in OC failure risk across BMI categories below 27.3, and risk above that level was fairly constant as well. The observed associations were stronger in subanalyses among OC users who reported no errors in method use: overweight consistent users were over twice as likely as other consistent users to become pregnant. In our earlier retrospective cohort study of OC failure,¹¹ while we were limited by lack of objective confirmation of reported pregnancies, less timely weight assessment, and the inability to evaluate OC use consistency, we found similar risk elevation for women in the highest BMI quartile (RR 1.7), and we also noted the suggestion of a threshold. The current study found weight-related risks of OC failure that were slightly lower than those for BMI; significant elevations were seen only among consistent users weighing more than 74.8 kg (OR 1.71) and more than 86.2 kg (OR 1.95). In this respect our findings are similar to those in a report of pooled data from 3 studies of the transdermal contraceptive patch.¹⁰ In that report of 3,319 patch users, 6 pregnancies occurred in the 80% of users weighing less than 74 kg, 2 occurred in the 10% weighing 74 to 80 kg or less, and 7 occurred in the 10% weighing 80 kg or more, with 5 of these 7 in the 3% of patch users who weighed 90 kg or more.

There are plausible biological mechanisms that may explain the relationships between high BMI or weight and OC failure. First, higher body weight is associated with increased basal metabolic rate,^15–17 which may shorten the duration of action of oral contraceptives. Second, drugs (such as OCs) that undergo phase II hepatic metabolism have shown increased clearance in obesity,^18,19 perhaps through induction of hepatic enzymes. Both of these metabolic changes may lead to insufficient serum drug levels for good contraceptive efficacy. A final possibility is that the increased volume of fat tissue in overweight women increases sequestration of lipophilic OCs, again leading to lower serum hormone levels. In support of these hypotheses, in some hormonal contraception studies, serum ethinyl E2 and progestin levels have been found to be negatively correlated with body weight and obesity.^20–23

The current study was conducted in a large health maintenance organization whose population closely mirrors the general population of the surrounding region.²⁴ A strength of the study was our ability to identify all cases coming to medical attention within this defined population and a random sample of representative controls from the population. However, case ascertainment was based on pregnancy information known to Group Health Cooperative; therefore, we may have missed enrollees’ pregnancies that were ascertained and attended elsewhere. Because pregnancy testing, abortion services, and prenatal and delivery care are available at Group Health Cooperative facilities without parental consent to enrollees 18 years of age and older, we think it unlikely that a substantial number of potential cases would have received care entirely outside of the health maintenance organization, and we have no reason to believe that missed cases would have a different weight distribution than those we identified. Similarly, if women who participated differed in BMI and weight from nonparticipants, there is the potential for bias in our results. However, cases and controls participated to roughly the same degree, and it seems unlikely that any BMI or weight differential between nonparticipants and participants would differ by case-control status. We found that cases and controls differed on a number of attributes that others have found to be correlates of OC failure (low income, cohabitation, black race), but after controlling for the matching variables age and reference year, parity was the only confounder in our analyses of BMI or weight and OC failure.

In this study we used Group Health Cooperative laboratory reports to ascertain pregnancy status and Group Health Cooperative pharmacy data to identify women who may have used OCs at the time of conception. Our confirmation of laboratory-reported pregnancies and details of reference-month OC prescriptions with study participants was likely to have provided more accurate information than using either medical data or participant self-reports alone. The differential between cases and controls in mean time from reference date to interview date may have influenced the accuracy of participant's reported data. However, the differential was only 24 days, and we found that there was no confounding of our results by time from reference date to interview date, reassuring us that this circumstance was not likely to have introduced bias in our results. To ascertain exposure status, we measured height at interview and asked participants for their reference-month weight. Agreement between medical record and self-reported weights was good and was nondifferential by case-control status. Consequently, we believe we obtained accurate information on reference-month weight in this well-educated health maintenance organization population. Any nondifferential misclassification of BMI or weight quartile would have resulted in a spurious attenuation of the true relative risks. We also relied on participant self-report to determine consistency of OC use during the reference month. It is possible that cases and controls differed in the accuracy of this reporting; thus, in this report we emphasize our overall results.

In conclusion, our findings suggest that being overweight may increase a woman's risk of becoming pregnant while using oral contraceptives. The absolute effect of this association, if causal, depends on the underlying population OC-related pregnancy rate. A 60% increase in risk in a population with an overall OC-related pregnancy rate similar to our study population would translate into 2 more pregnancies per 100 woman-years of use in overweight women than in normal-weight women, whereas the same percentage increase in a population with OC-related pregnancy rates as estimated in the 1995 National Survey of Family Growth⁵ would mean an additional 4 pregnancies per 100 woman-years of use among overweight women. Given the progressively higher prevalence of overweight and obesity in the United States in recent years,²⁵ elevated BMI may be an increasingly important cause of unintended pregnancy among OC users. Consideration of additional or effective alternative contraceptive methods is warranted for overweight women.

	Footnotes

 
This project was supported by grant 1 R01 HD-34712 from the U.S. National Institute of Child Health and Human Development.

The authors thank the Fred Hutchinson Cancer Research Center study personnel, Sheila Farr, Andrea Krattli, and Patty Pride, and Group Health Cooperative study personnel, Jane Grafton, Pat Middleton, Kelli O'Hara, and Patricia Yarbro, for their contributions to the study.

Received July 6, 2004. Received in revised form October 4, 2004. Accepted October 7, 2004.

doi:10.1097/01.AOG.0000149155.11912.52

	REFERENCES

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
1. Woutersz TB, Korba VD. Five-year, multicenter study of a triphasic, low-dose, combination oral contraceptive. Int J Fertil 1988;33:406–10.[Medline]

2. Friedman AJ, Wheeler J. Efficacy and safety of ethynodiol diacetate, 1 mg, with ethinyl estradiol, 35 µg, with an emphasis on contraceptive efficacy: a phase IV trial. J Reprod Med 1991;36(suppl):328–33.[Medline]

3. London RS, Chapdelaine A, Upmalis D, Olson W, Smith J. Comparative contraceptive efficacy and mechanism of action of the norgestimate-containing triphasic oral contraceptive. Acta Obstet Gynecol Scand Suppl 1992;156:9–14.[Medline]

4. Hatcher RA, Trussell J, Stewart F, Cates W, Stewart GK, Guest F, et al. Contraceptive technology. 17th rev ed. New York (NY): Ardent Media; 1998.

5. Fu H, Darroch JE, Haas T, Ranjit N. Contraceptive failure rates: new estimates from the 1995 National Survey of Family Growth. Fam Plann Perspect 1999;31:56–63.[Medline]

6. Abma J, Chandra A, Mosher W, Peterson L, Piccinino L. Fertility, family planning and women's health: new data from the 1995 National Survey of Family Growth. Vital Health Stat 23 1997;19:1–114.

7. Brown S, Eisenberg L. The best intentions: unintended pregnancy and the well-being of children and families. Washington, DC: National Academy Press; 1995.

8. Gu S, Sivin I, Du M, Zhang L, Ying L, Meng F, et al. Effectiveness of Norplant implants through seven years: a large-scale study in China. Contraception 1995;52:99–103.[Medline]

9. Grubb GS, Moore D, Anderson NG. Pre-introductory clinical trials of Norplant implants: a comparison of seventeen countries’ experience. Contraception 1995;52:287–96.[Medline]

10. Zieman M, Guillebaud J, Weisberg. E, Shangold GA, Fisher AC, Creasy GW. Contraceptive efficacy and cycle control with the Ortho Evra/Evra transdermal system: the analysis of pooled data. Fertil Steril 2002;77 suppl 2:S13–8.

11. Holt VL, Cushing-Haugen KL, Daling JR. Body weight and risk of oral contraceptive failure. Obstet Gynecol 2002;99:820–7.[Abstract/Free Full Text]

12. Healthy people 2000: national health promotion and disease prevention objectives. Washington, DC: U.S. Department of Health and Human Services, Public Health Service; 1990.

13. Najjar MF, Rowland M. Anthropometric reference data and prevalence of overweight, United States, 1976-80. Hyattsville (MD): U.S. Dept. of Health and Human Services, Public Health Service, National Center for Health Statistics; 1987.

14. Maldonado G, Greenland S. Simulation study of confounder selection strategies. Am J Epidemiol 1993;138:923–36.[Abstract/Free Full Text]

15. Ravussin E, Burnand B, Schutz Y, Jequier E. Twenty-four-hour energy expenditure and resting metabolic rate in obese, moderately obese, and control subjects. Am J Clin Nutr 1982;35:566–73.[Abstract/Free Full Text]

16. Owen OE, Kavle E, Owen RS, Polansky M, Caprio S, Mozzoli MA, et al. A reappraisal of caloric requirements in healthy women. Am J Clin Nutr 1986;44:1–19.[Abstract/Free Full Text]

17. Dietz WH. Obesity. J Am Coll Nutr 1989;8(suppl):13S–21S.

18. Abernethy DR, Greenblatt DJ. Drug disposition in obese humans: an update. Clin Pharmacokinet 1986;11:199–213.[Medline]

19. Speerhas R. Drug metabolism in malnutrition and obesity: clinical concerns. Cleve Clin J Med 1995;62:73–5.[Medline]

20. Stadel BV, Sternthal PM, Schlesselman JJ, Douglas MG, Hall WD, Kaul L, et al. Variation of ethinylestradiol blood levels among healthy women using oral contraceptives. Fertil Steril 1980;33:257–60.[Medline]

21. Andersen AN, Lebech PE, Sorensen TIA, Borggaard B. Sex hormone levels and intestinal absorption of estradiol and D-norgestrel in women following bypass surgery for morbid obesity. Int J Obes 1982;6:91–6.

22. Fishman J, Boyar R, Hellman L. Influence of body weight on estradiol metabolism in young women. J Clin Endocrinol Metab 1975;41:989–91.[Abstract]

23. Bleau G, Roberts KD, Chapdelaine A. The in vitro and in vivo uptake and metabolism of steroids in human adipose tissue. J Clin Endocrinol Metab 1974;39:236–46.[Medline]

24. Saunders KW, Stergachis A, Von Korff M. Group Health Cooperative of Puget Sound. In: Strom BL, editor. Pharmacoepidemiology. 2nd ed. Chichester (UK): John Wiley & Sons; 1994. p. 171–86.

25. Flegal KM, Carroll MD, Ogden CL, Johnson CL. Prevalence and trends in obesity among U.S. adults; 1999-2000. JAMA 2002;288:1723–7.[Abstract/Free Full Text]

This article has been cited by other articles:

				Contraception in Women with Medical Problems Journal Watch Women's Health, January 31, 2008; 2008(131): 2 - 2. [Full Text]

				L. R. Brunner Huber and J. L. Toth Obesity and Oral Contraceptive Failure: Findings from the 2002 National Survey of Family Growth Am. J. Epidemiol., December 1, 2007; 166(11): 1306 - 1311. [Abstract] [Full Text] [PDF]

				A. E. Bonny, J. Ziegler, R. Harvey, S. M. Debanne, M. Secic, and B. A. Cromer Weight Gain in Obese and Nonobese Adolescent Girls Initiating Depot Medroxyprogesterone, Oral Contraceptive Pills, or No Hormonal Contraceptive Method Arch Pediatr Adolesc Med, January 1, 2006; 160(1): 40 - 45. [Abstract] [Full Text] [PDF]

				P. J. Meis, M. Klebanoff, M. P. Dombrowski, B. M. Sibai, S. Leindecker, A. H. Moawad, A. Northen, J. D. Iams, M. W. Varner, S. N. Caritis, et al. Does Progesterone Treatment Influence Risk Factors for Recurrent Preterm Delivery? Obstet. Gynecol., September 1, 2005; 106(3): 557 - 561. [Abstract] [Full Text] [PDF]

				M. D. Creinin and E. Roberts Body Mass Index, Weight, and Oral Contraceptive Failure Risk Obstet. Gynecol., June 1, 2005; 105(6): 1492 - 1492. [Full Text] [PDF]

				Overweight Women at Higher Risk for OC Failure Journal Watch Women's Health, February 22, 2005; 2005(222): 4 - 4. [Full Text]

				Overweight Women at Increased Risk for Oral Contraceptive Failure Journal Watch (General), January 28, 2005; 2005(128): 4 - 4. [Full Text]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Holt, V. L. Articles by Daling, J. R. Search for Related Content PubMed PubMed Citation Articles by Holt, V. L. Articles by Daling, J. R. Related Collections Contraception Epidemiology/public health General gynecology