Asthma and Pregnancy

FACTORS that precipitate asthmatic attacks are complex,¹and there are conflicting views regarding the reciprocal effects of asthma and pregnancy. Since the incidence of asthma in pregnancy is 0.4% to 1.3%,²,³the association is of concern to physicians who must counsel asthmatic women who are or wish to become pregnant. After reviewing the literature on the coexisting asthma and pregnancy, we suggest a rational approach toward optimal management of asthma in a pregnant patient. PHYSIOLOGY OF PREGNANCY Oxygenation of the Fetus The uteroplacental circulation is a low-pressure, highly vascular system developed by the 12th week. It acts as an arteriovenous shunt and decreases total systemic circulatory resistance. Maternal response is an increased cardiac output. Uterine blood flow increases to 20% of the cardiac output at the 26th to 30th week of pregnancy. There is a drop in Po₂across the placenta, and the fetus normally thrives in relative