Serial Studies of Renal Function During Pregnancy and the Puerperium in Normal Women12

Abstract

Until recently there has been uncertainty as to whether kidney function in normal pregnancy differs significantly from that in the nonpregnant state. The earlier studies reviewed by Smith (1), Chesley (2) and Bucht (3) were for the most part limited to the immediate pre-and postpartum period when deviations from the nonpregnant state are less marked. On the other hand, the studies of Nice (4) demonstrated a marked increase of urea clearance in mid-pregnancy while those of Bonsnes and Lange (5) and Bucht (3) showed significant increases in both renal plasma flow and in glomerular filtration rate during mid-pregnancy which persisted to approximately the thirtyeighth week.At the time the present study was begun, no serial studies of renal function during normal pregnancy and in the postpartum period had been reported and it was the purpose of this study to make such observations. Serial studies eliminate the element of apprehension encountered in single studies which, as emphasized by Miles and DeWardener (6), may distort the results. Our findings confirm the increased renal function in pregnancy, and define the resultant lowering of the normal range of values for plasma urea averaging 27 years. One subject (K) was studied during a second pregnancy. Their parity was from one to five children, with an average of two children. No patient exhibited any suggestion of toxemia during the study or during any previous pregnancy, nor was there any evidence of hypertension or urologic disease. One patient (E) was delivered by cesarean section at 38 weeks because of a placenta previa, and another (H) spontaneously delivered twins at 34 weeks. A group of nine nonpregnant women were control subjects. One of the control subjects (N) subsequently became pregnant. The average age was 25.7 years, with a range of 21 through 33 years and an average parity of 1.1. Procedure. Renal clearances of para-aminohippurate (PAH) and of inulin were determined by the constant infusion technique of Goldring and Chasis (7). When creatinine clearances were measured, meat was eliminated from the diet, as recommended by Camara, Arn, Keimer and Newburgh (8). During the period of study, the patients were in a semi-supine position. For comparison, studies were also made on seven subj ects in both supine and left lateral positions. A minimum of three collection periods of 15 to 30 minutes in length, depending on the urine flow, were employed. Each period was terminated by irrigation of the bladder with 100 to 200 ml. of physiological saline solution and 50 to 100 ml. of air, both of which were totally recovered before the next period was begun. In a subsequent series of clearance studies during pregnancy (9), the patients were asked to stand at the end of the collection period. In only one instance was more than a few additional ml. of urine obtained. These observations in conjunction with those of Chesley and co-workers (10), who found that during pregnancy no better results could be obtained by direct irrigation of the renal pelves, suggest that re...

Course of preeclamptic glomerular injury after delivery

“…These women were randomly selected from the obstetric ward or responded to advertisements posted throughout the hospital. Thirty-nine healthy female volunteers of reproductive age (20 -48 yr) provided control values for the corresponding studies of preeclampsia on day 25, by which time the hyperfiltration accompanying a normal gravid state has been restored to nongravid levels (31). Each patient consented to undergo a detailed study of glomerular function that was approved by the Institutional Review Board at Stanford University.…”

Obstetric Nephrology

“…Thus, our current knowledge of GFR and RPF in normal pregnancy is derived from a handful of serial studies with small sample sizes in which varying methodologies could produce remarkable differences in the estimates of renal hemodynamics. There is variation among studies in the positioning of patients: semi-supine, recumbent, sitting, and left lateral decubitus (2,(27)(28)(29). Some investigators have reported that the interplay of the supine position and the size of the gravid uterus may lead to compression of the inferior vena cava, resulting in decrements in cardiac output, RPF, and GFR (30).…”

“…Some investigators have reported that the interplay of the supine position and the size of the gravid uterus may lead to compression of the inferior vena cava, resulting in decrements in cardiac output, RPF, and GFR (30). However, other investigators have failed to demonstrate any effect of patient position on renal hemodynamics in late pregnancy (28,31). Serial studies have also differed in the process for ensuring complete bladder emptying during urinary inulin and p-aminohippurate clearances.…”

“…Serial studies have also differed in the process for ensuring complete bladder emptying during urinary inulin and p-aminohippurate clearances. Whereas some investigators used bladder catheterization (28), others instructed patients to spontaneously void (2,29). Given the potential for urodynamic changes due to the gravid uterus, the risk of urinary retention, inadequate emptying, and incomplete urine collections is elevated in pregnancy and this can lead to errors in clearance methodology.…”

Circulating β-2-microglobulin levels during pregnancy and their possible relationship with feto-maternal histocompatibility

“…To our knowledge, no decreased 02m levels have been reported so far. During pregnancy, glomerular filtration rate [8] as well as plasma volume are increased. Since plasma 02m levels are not decreased but rather increased it must be assumed that during pregnancy the production of j32m is enhanced [ the close association between )32m and HLA antigens it seemed interesting to measure plasma 02m in normal and pathological pregnancies and to relate the values obtained to the degree of histoincompatibility between mother and fetus.…”