Basal metabolic rate in hyperemesis gravidarum: comparison to normal pregnancy and response to treatment.

Objective: The aim of the study was to measure resting minute ventilation and oxygen consumption in patients with hyperemesis gravidarum before and after treatment and to compare the results with those of normal pregnant women.

Study Design: Baseline evaluation was performed with the use of an open-circuit ventilatory system in 17 hospitalized patients with hyperemesis gravidarum and was repeated 1 week after treatment. Thirty-seven normal pregnant women served as control subjects.

Results: Resting minute ventilation and oxygen consumption were decreased by 20% and 15% (P <.001), respectively, in patients with hyperemesis compared with control subjects. The decrease occurred despite a measurable increase of free thyroxine compared with normal pregnancy. Treatment resulted in a 10% increase in oxygen consumption in those patients with increased thyroid stimulation, but not otherwise.

Conclusion: Resting oxygen consumption is reduced significantly in patients with hyperemesis gravidarum that is consistent with a state of partial starvation rather than increased in parallel with increases of thyroid axis activity.