SERIAL CHANGES IN 24 HOUR CREATININE CLEARANCE DURING NORMAL MENSTRUAL CYCLES AND THE FIRST TRIMESTER OF PREGNANCY

Abstract

Serial changes in 24 h creatinine clearance were determined in 11 women during several menstrual cycles before conception, the conceptional cycle and the 1st trimester of pregnancy. During the menstrual cycle, a 20% mean increase occurred between the week of menstruation and the late luteal phase. Following conception, this increase continued such that a 45% mean increase was evident by the 9th wk of gestation. In 2 women who aborted spontaneously, the change in 24 h creatinine clearance in early pregnancy was not as great nor as sustained; this feature was apparent at least 3 wk before any clinical abnormality. Possible reasons for the changes in glomerular filtration rate in early pregnancy and its clinical implications are discussed.