Oral contraceptive use and acute mountain sickness in South Pole workers.

Introduction: Progesterone has a number of properties that could influence the development of acute mountain sickness (AMS), including anti-inflammation, respiratory smooth muscle relaxation, ventilatory stimulation, and antidiuretic characteristics. Oral contraceptive (OC) use decreases levels of circulating progesterone by preventing ovulation. We hypothesized rates of AMS development would be significantly higher in OC users as compared to Non-OC users in a population traveling rapidly to the South Pole.

Methods: There were 50 female subjects (OC N = 13, no OC N = 37) who traveled by airplane from Sea Level (SL) to Altitude (ALTD) (-3200 m) in < 4 h and were monitored for the development of AMS. SL and ALTD measurements of anthropometrics, vital signs, hematologic variables, blood chemistries, electrolytes, endocrine responses, and pulmonary function were assessed with t-test and Chi-square analyses, P < 0.05.

Results: As compared to Non-OC users, OC users had lower progesterone levels (ng x ml(-1)) at SL (0.7 +/- 0.5 vs. 3.2 +/- 4.6) and at ALTD (0.7 +/- 0.7 vs. 3.1 +/- 4.6). AMS was significantly more prevalent in OC users (85%) as compared to Non-OC users (51%). Acetazolamide prophylaxis was not protective, with a greater proportion of OC users (100%) developing AMS despite its use as compared to Non-OC users (50%). Blood pressure responses also differed significantly, with OC users displaying higher mean arterial pressures at ALTD vs. Non-OC users.

Conclusion: OC use at ALTD is associated with an increased risk for the development of AMS. Acetazolamide prophylaxis with OC use was also associated with an increased rate of AMS development.