Predicting Risk of Ovulation in New Start Oral... : Obstetrics & Gynecology (original) (raw)

ORIGINAL RESEARCH

Predicting Risk of Ovulation in New Start Oral Contraceptive Users

Schwartz, Jill L. MD; Creinin, Mitchell D. MD; Pymar, Helen C. MD; Reid, Lynn PA-C

Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine and Magee Womens Research Institute, Pittsburgh, Pennsylvania.

Address reprint requests to: Mitchell D. Creinin, MD, University of Pittsburgh School of Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, Magee-Womens Hospital, 300 Halket Street, Pittsburgh, PA 15213–3180. E-mail: [email protected].

The authors gratefully acknowledge Leslie A. Meyn, MS, for her statistical and editorial support.

Financial Disclosure This research was supported by a grant from Wyeth-Ayerst Laboratories. The authors received no salary support to perform this study. Drs. Schwartz and Creinin have received research support and honoraria from Wyeth-Ayerst Laboratories.

Received June 19, 2001. Received in revised form September 13, 2001. Accepted October 2, 2001.

OBJECTIVE

To assess ovarian follicular development and ovulation rates in women starting to take oral contraceptives (OC) on menstrual cycle day 1, 4, or 7.

METHODS

One hundred thirty women starting treatment with OC were randomized to begin use of ethinyl estradiol, 30 μg, plus norgestrel, 300 μg, on menstrual cycle day 1 (group 1), 4 (group 2), or 7 (group 3). Follicular development was assessed by vaginal ultrasonography on menstrual cycle days 7, 14, 21, and 28, and serum progesterone levels were measured on menstrual cycle days 21 and 28. At a .05 level of significance (two-tailed) and power of 80%, 84 participants were required to complete the study. Eighty-five women who met study criteria, made minimal dosing errors, and underwent at least three ultrasonographic examinations were analyzed.

RESULTS

A follicle-like structure that reached a maximum diameter over 13 mm was observed in three of 29 (10.3%), five of 29 (17.2%), and 12 of 27 (44.4%) women in groups 1, 2 and 3, respectively (P = 0.003). The median maximum follicle size for each group was 9.0 mm, 9.0 mm, and 12.0 mm for start day 1, 4, and 7 respectively (P < .001). Evidence of ovulation based on serum progesterone was present in two, one, and zero women in groups 1, 2, and 3, respectively (P = .2).

CONCLUSION

Although a delay in oral contraceptive initiation results in significantly more ovarian follicular development, the postponement does not appear to increase actual ovulation rates.