Phthalates and risk of endometriosis and leiomyomata the pattern of these findings, with OR = 0.49 (95% CI, 0.12–1.93) for endometriosis (57 cases) and OR = 1.63 (95% CI, 0.89–2.96) for uterine leiomyomata (113 cases). Urinary concentrations of MEP and MBzP were not appreciably associated with risk of endometriosis or leiomyomata. Because cur- rent pregnancy was more common with higher urinary MBzP and less common in both out- comes, we repeated analyses of MBzP excluding pregnant women, but the results were similar. Moreover, our results overall did not change after further adjustment for parity or use of oral contraceptives or when we excluded women who used oral contraceptives. They also did not change substantially when we replaced the creatinine-corrected urinary phthalate con- centrations with uncorrected concentrations or when we included women with extreme urinary creatinine concentrations. Discussion In this large nationally representative cross- sectional study, in which we used urinary phthalate metabolite concentrations as bio- markers of exposure to four parent phthalates, we observed weak positive associations for uri- nary MBP, and weak inverse associations for urinary MEHP, in relation to self-reported history of endometriosis and leiomyomata. Our analyses of the two oxidative metabolites of DEHP—MEHHP and MEOHP—yielded findings that were consistent with our findings for MEHP with respect to endometriosis, but not with respect to uterine leiomyomata. We found little evidence for associations of urinary MEP and MBzP with each of these outcomes. Our results for MEHP and endometriosis do not agree with findings from the three case– control studies on this subject, all which identi- fied positive associations between markers of DEHP exposure and risk of endometriosis. Cobellis et al. (2003) reported higher plasma DEHP concentrations [median, 0.57 µg/mL; interquartile range (IQR), 0.06–1.23] among women with endometriosis than among con- trols (0.18 µg/mL; IQR, 0–0.44; p = 0.005). However, plasma MEHP concentrations were generally low and did not differ between the outcome groups: for cases the median MEHP was 0.38 µg/mL (IQR, 0.1–0.97), and for controls the median was 0.58 µg/mL (IQR, 0.34–0.71). Our MEHP results also diverge from a subsequent case–control study by Reddy et al. (2006), in which women with laparoscopy-confirmed endometriosis had significantly higher plasma concentrations of DEHP compared with controls, and concen- trations appeared more elevated with increas- ingly severe stage of endometriosis. In a third case–control study by Itoh et al. (2009), Table 3. Adjusteda ORs of endometriosis or uterine leiomyomata by concentration of creatinine-corrected urinary phthalate metabolite, in quartiles (1999–2004). Endometriosis Lowest Q Second Q Third Q Highest Q Highest vs. lowest three Qs Excluding women who had diagnosis or hysterectomy > 10 years ago > 7 years ago Uterine leiomyomata Lowest Q Second Q Third Q Highest Q Cases/n 22/303 20/306 22/310 23/308 MBP OR (95% CI) 1.00 Reference 0.75 (0.38–1.47) 0.96 (0.49–1.91) 1.24 (0.65–2.34) ptrend = 0.3 Cases/n 28/304 20/309 18/304 21/310 MEP MEHP OR (95% CI) Cases/n OR (95% CI) 1.00 Reference 0.89 (0.44–1.82) 1.13 (0.56–2.27) 1.12 (0.53–2.35) ptrend = 0.6 28/309 1.00 Reference 21/303 0.78 (0.38–1.58) 23/309 0.89 (0.42–1.90) 15/306 0.39 (0.16–0.95) ptrend = 0.05 Cases/n 23/306 19/306 23/309 22/306 MBzP OR (95% CI) 1.00 Reference 0.84 (0.37–1.89) 1.17 (0.47–2.94) 1.17 (0.42–3.27) ptrend = 0.6 Highest Lowest Q three Qs OR (95% CI) 23/308 64/919 1.36 (0.77–2.41) Highest Lowest Q three Qs OR (95% CI) 21/310 66/917 1.12 (0.58–2.17) Highest Lowest Q three Qs OR (95% CI) 15/306 72/921 0.44 (0.19–1.02) Highest Lowest Q three Qs OR (95% CI) 22/306 65/921 1.16 (0.58–2.33) 11/289 9/284 36/857 29/844 1.47 (0.70–3.10) 1.45 (0.64–3.28) 10/290 7/285 37/856 31/843 0.87 (0.30–2.51) 0.80 (0.23–2.76) 5/284 4/282 42/862 34/846 0.21 (0.06–0.74) 0.19 (0.05–0.78) 13/292 8/286 34/854 30/842 1.55 (0.55–4.37) 0.94 (0.28–3.12) 33/301 29/305 39/308 50/307 1.00 Reference 0.66 (0.40–1.10) 0.76 (0.46–1.28) 1.26 (0.70–2.27) ptrend = 0.2 41/301 31/309 45/303 34/308 1.00 Reference 0.72 (0.35–1.46) 1.29 (0.74–2.25) 0.85 (0.47–1.54) ptrend = 0.9 43/307 37/301 42/307 29/306 1.00 Reference 1.03 (0.59–1.80) 1.13 (0.65–1.95) 0.66 (0.35–1.26) ptrend = 0.2 37/306 36/302 47/309 31/304 1.00 Reference 1.11 (0.59–2.07) 1.16 (0.64–2.13) 1.14 (0.54–2.39) ptrend = 0.8 Highest Lowest Q three Qs OR (95% CI) Highest vs. lowest three Qs 50/307 101/914 1.56 (0.93–2.61) Excluding women who had diagnosis or hysterectomy > 10 years ago 30/281 66/853 1.61 (0.86–3.01) > 7 years ago 26/274 53/838 1.86 (0.94–3.68) > 5 years ago 23/269 44/827 1.87 (0.96–3.65) Endometriosis or uterine leiomyomata Lowest Q 42/301 1.00 Reference Second Q 41/305 0.74 (0.46–1.20) Third Q 53/308 0.97 (0.62–1.53) Highest Q 65/307 1.55 (0.87–2.75) ptrend = 0.03 Highest Lowest Q three Qs OR (95% CI) 34/308 117/913 0.86 (0.51–1.46) Highest Lowest Q three Qs OR (95% CI) 29/306 122/915 0.63 (0.35–1.12) Highest Lowest Q three Qs OR (95% CI) 31/304 120/917 1.04 (0.57–1.92) 25/291 20/285 19/283 71/843 59/827 48/813 1.10 (0.60–2.01) 1.14 (0.58–2.26) 1.35 (0.68–2.68) 17/284 14/281 12/278 79/850 65/831 55/818 0.60 (0.30–1.23) 0.57 (0.26–1.29) 0.60 (0.27–1.36) 22/291 21/288 19/284 74/843 58/824 48/812 0.97 (0.45–2.08) 1.22 (0.55–2.74) 1.33 (0.59–3.00) 59/301 44/309 55/303 43/308 1.00 Reference 0.75 (0.45–1.24) 1.15 (0.75–1.78) 0.80 (0.49–1.30) ptrend = 0.6 60/307 1.00 Reference 50/301 0.93 (0.56–1.54) 52/307 0.94 (0.57–1.55) 39/306 0.57 (0.33–0.98) ptrend = 0.03 48/306 47/302 61/309 45/304 1.00 Reference 1.01 (0.55–1.83) 1.25 (0.70–2.24) 1.27 (0.59–2.72) ptrend = 0.5 Highest vs. lowest three Qs Excluding women who had diagnosis or hysterectomy > 10 years ago > 7 years ago > 5 years ago Highest Lowest Q three Qs OR (95% CI) 65/307 136/914 1.71 (1.07–2.75) Highest Lowest Q three Qs OR (95% CI) 43/308 158/913 0.83 (0.51–1.37) Highest Lowest Q three Qs OR (95% CI) 39/306 162/915 0.59 (0.37–0.95) Highest Lowest Q three Qs OR (95% CI) 45/304 156/917 1.16 (0.66–2.05) 38/275 32/268 27/262 80/835 66/819 54/806 2.04 (1.12–3.45) 2.16 (1.23–3.77) 2.08 (1.14–3.80) 27/286 21/279 18/275 91/824 77/808 63/793 0.88 (0.50–1.54) 0.91 (0.48–1.72) 0.95 (0.50–1.80) 20/278 16/274 14/272 98/832 82/823 67/796 0.54 (0.28–1.02) 0.50 (0.24–1.02) 0.53 (0.25–1.13) 29/284 24/278 22/275 89/826 74/809 59/793 1.25 (0.62–2.52) 1.19 (0.60–2.34) 1.38 (0.66–2.87) Q, quartile. aAdjusted for age, race/ethnicity, age at menarche, current pregnancy status, and current breast-feeding status. Environmental Health Perspectives • volume 118 | number 6 | June 2010 829