progestin alone or with estrogen raised ve at rest and decreased end-tidal pco2 ( petco2 ) by 3.9 +/- 0.8 and 3.3 +/- 0.6 torr , respectively ( both p less than 0.05 ) , accounting for approximately one-fourth of the rise in ve and three-fourths of the petco2 reduction seen at full-term pregnancy .
C0014939
estrogen
C0032961
pregnancy