OR19-1 The Point Prevalence of Ovulation in a Large Population-based Sample of Spontaneously, Regularly Menstruating Women. The HUNT Study, Norway

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: OR19-Female Reproductive Endocrinology
Sunday, June 16, 2013: 11:15 AM-12:45 PM
Presentation Start Time: 11:15 AM
Room 102 (Moscone Center)
Jerilynn C Prior*1, Marit Naess2, Arnulf Langhammer3 and Siri Forsmo2
1University of British Columbia, Vancouver, BC, Canada, 2Norwegian U. of Science and Technology (NTNU), Trondheim, Norway, 3Nord-Trondelag Health Survey (HUNT), Trondheim, Norway
Ovulatory menstrual cycles are essential for fertility and are associated with positive premenopausal bone change (1;2), fewer heart attacks (3) and breast cancers (4). However, there are few population-based, hormonally confirmed data on ovulation prevalence. This CIHR-funded Canadian-Norway collaboration assessed the prevalence of ovulation in the semi-rural county of Nord-Trondelag (5) in 2006-8 (HUNT3) in 3709 spontaneously (no hormonal contraception) menstruating women ages 20-49.9 with a 58.8% participation rate. All reported the start of last flow, usual cycle length and regularity in the last 12 mo. (Y/N), had body mass index (BMI, kg/m2) and a single progesterone (P4) and estradiol (E2) level measured. Women with irregular cycles (n=437,12.8%) had similar parity, menarche age, past hormonal contraceptive and current alcohol use but were more likely to be >45 y, have higher BMIs (27.3 vs. 26.3), be current smokers (45.5 vs. 29.7%), exercise less, have lower self-reported health and report more infertility and past amenorrhea. Evidence of ovulation was assessed in the 3,174 women with complete reproductive and hormonal data and regular, normal-length (NL) cycles (21-35 d). The two criteria used to assess presumed ovulation were: 1) a serum progesterone level of ³9.54nmol/L (6); 2) samples on cycle days 14 to 3 days before expected flow based on usual cycle length. This analysis cohort (n=3174) was median age 41.7 (IQR 36.8/45.5), with median cycle length 28 days (IQR 28/28) d. and BMI 26.3 (26.1; 26.4) of whom 18.5% were obese (BMI>30), 95.6% parous and 61.3% reporting >2 hours/week of physical activity. 1,321 women were sampled in the presumed luteal phase (as described)—the point prevalence of ovulation was 56.3% with P4 ³9.54nmol/L. Those women with apparent ovulatory (n=744) vs. anovulatory cycles (n=577)  did not differ in mean age, parity, BMI, menarche age, or any variables except the median cycle day of sampling (19 vs.17) and in having higher P4 (25.0) and E2 (0.29) nmol/L levels. A sub-cohort of 265 women also reporting next flow had 117 with NL cycles sampled cycle days 14 to -3—ovulation prevalence was 65.8%. With a P4 threshold of ³8.0 nmol/L (7) (excluding the follicular phase) in the analysis cohort, the point prevalence of ovulation was 59.4%. In summary, these population-based data suggest that the point prevalence of ovulation in spontaneous, regular, normal length cycles is 56.3 to 65.8% and lower than anticipated.

(1)   Prior JC, Vigna YM, Schechter MT, Burgess AE. Spinal bone loss and ovulatory disturbances. N Engl J Med 1990; 323:1221-1227.   (2)   Sowers M, Randolph JF, Crutchfield M, Jannausch ML, Shapiro B, Zhang B et al. Urinary ovarian and gonadotropin hormone levels in premenopausal women with low bone mass. J Bone Min Res 1998; 13(7):1191-1202.   (3)   Gorgels WJ, Graaf Y, Blankenstein MA, Collette HJ, Erkelens DW, Banga JD. Urinary sex hormone excretions in premenopausal women and coronary heart disease risk: a nested case-referent study in the DOM-cohort. J Clin Epidemiol 1997; 50(3):275-281.   (4)   Cowan LD, Gordis L, Tonascia JA, Jones GS. Breast cancer incidence in women with a history of progesterone deficiency. Am J Epidemiol 1981; 114(2):209-217.   (5)   Holmen J, Midthjell K, Kruger G, Lagnhammer A, Holmen TL, Brathberg GH et al. The Nord-Trondelag health study 1995-97 (HUNT 2).  Objectives, contents, methods and participation. Norwegian J Epid 2004; 13(1):19-32.   (6)   Israel R, Mishell DR, Jr., Stone SC, Thorneycroft IH, Moyer DL. Single luteal phase serum progesterone assay as an indicator of ovulation. Am J Obstet Gynecol 1972; 112(8):1043-1046.   (7)   Naess M. Ovulation frequency in women of childbearing age attending a population based health survey.  The relationship between self-reported cycles and measured serum progesterone levels in the North-Trondelag health study, the HUNT3 Survey, 2006-2008. Institute of Community Medicine, University of Tromso UIT, 2011.

Nothing to Disclose: JCP, MN, AL, SF

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

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