Maternal kidney function during pregnancy: systematic review and meta-analysis.

OBJECTIVES: To review systematically current literature on kidney function changes during pregnancy, in order to estimate the extent of adaptation over the course of both healthy physiological and complicated singleton pregnancies, and to determine healthy pregnancy reference values. METHODS: PubMed (NCBI) and EMBASE (Ovid) electronic databases were searched, from inception to July 2017, for studies on kidney function during uncomplicated and complicated pregnancies. Included studies were required to report a non-pregnant reference value of kidney function (either in a non-pregnant control group or as a prepregnancy or postpartum measurement) and a pregnancy measurement at a predetermined and reported gestational age. Kidney function measures assessed were glomerular filtration rate (GFR) measured by inulin clearance, GFR measured by creatinine clearance and serum creatinine level. Pooled mean differences between pregnancy measurements and reference values were calculated for predefined intervals of gestational age in uncomplicated and complicated pregnancies using a random-effects model described by DerSimonian and Laird. RESULTS: Twenty-nine studies met the inclusion criteria and were included in the analysis. As early as the first trimester, GFR was increased by up to 40-50% in physiological pregnancy when compared with non-pregnant values. Inulin clearance in uncomplicated pregnancy was highest at 36-41 weeks, with a 55.6% (53.7; 95% CI, 44.7-62.6 mL/min) increase when compared with non-pregnant values, and creatinine clearance was highest at 15-21 weeks' gestation, with a 37.6% (36.6; 95% CI, 26.2-46.9 mL/min) increase. Decrease in serum creatinine level in uncomplicated pregnancy was most prominent at 15-21 weeks, with a 23.2% (-0.19; 95% CI, -0.23 to -0.15 mg/dL) decrease when compared with non-pregnant values. Eight studies reported on pregnancies complicated by a hypertensive disorder. Meta-regression analysis showed a significant difference in all kidney function parameters when comparing uncomplicated and hypertensive complicated pregnancies. CONCLUSIONS: In healthy pregnancy, GFR is increased as early as the first trimester, as compared with non-pregnant values, and the kidneys continue to function at a higher rate throughout gestation. In contrast, kidney function is decreased in hypertensive pregnancy. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Physiological adaptation of endothelial function to pregnancy: systematic review and meta-analysis.

OBJECTIVES: To establish reference values for flow-mediated dilatation (FMD) and brachial artery diameter (BAD) in pregnancy and to provide insight into the physiological and pathological course of endothelial adaptation throughout human singleton pregnancy. METHODS: A meta-analysis was performed following a systematic review of current literature on FMD, as a derivative for endothelial function, and BAD, throughout uncomplicated and complicated pregnancy. PubMed (NCBI) and EMBASE (Ovid) electronic databases were used for the literature search, which was performed from inception to 9 June 2016. To allow judgment of changes in comparison with the non-pregnant state, studies were required to report both non-pregnant mean reference of FMD (matched control group, prepregnancy or postpartum measurement) and mean FMD at a predetermined and reported gestational age. Pooled mean differences between the reference and pregnant FMD values were calculated for predefined intervals of gestational age. RESULTS: Fourteen studies that enrolled 1231 participants met the inclusion criteria. Publication dates ranged from 1999 to 2014. In uncomplicated pregnancy, FMD was increased in the second and third trimesters. Between 15 and 21 weeks of gestation, absolute FMD increased the most, by a mean (95% CI) of 1.89% (0.25-3.53%). This was a relative increase of 22.5% (3.0-42.0%) compared with the non-pregnant reference. BAD increased progressively, in a steady manner, by the second trimester but not significantly in the first half of the second trimester. We could not discern differences in FMD and BAD between complicated and uncomplicated pregnancies at 29-35 weeks' gestation, reported in the three studies that met our inclusion criteria. Despite the increase in FMD and BAD throughout gestation, both reference curves were characterized by wide 95% CIs. CONCLUSION: During healthy pregnancy, endothelium-dependent vasodilatation and BAD increase. Women with a complicated pregnancy had FMD values within the lower range when compared with those with uncomplicated pregnancy but, as a group, did not differ from each other. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Early pregnancy circulatory adaptation and recurrent hypertensive disease: an explorative study.

INTRODUCTION: Hypertensive pregnancy disorders are assumed to be preceded by defective spiral artery remodeling. Whether this localized aberration at the implantation site affects the initial maternal systemic cardiovascular and renal adaptation to pregnancy is unclear. We explored in a high-risk population, whether the initial systemic maternal adaptation to pregnancy differs between women who do and do not develop a recurrent hypertensive disorder later on in pregnancy. METHODS: We enrolled 61 normotensive women with a previous hypertensive disorder of pregnancy and subdivided them into 2 subgroups, based on whether or not their next pregnancy remained uneventful (n = 33) or became complicated by a recurrent hypertensive disorder (n = 28). We measured before pregnancy and again at 18 ± 2 weeks of gestation cardiac output, blood pressure, plasma volume, creatinine clearance, and calculated total peripheral vascular resistance from cardiac output and blood pressure. RESULT: Both subgroups responded to pregnancy with an increase in cardiac output, plasma volume, heart rate, and creatinine clearance, and a decrease in blood pressure and total peripheral vascular resistance. Women who developed a recurrent hypertensive disorder differed from their counterparts with an uneventful next pregnancy by smaller pregnancy-induced increases in creatinine clearance (19% vs. 31%, P = .035) and cardiac output (10% vs. 20%, P = .035), respectively. CONCLUSION: The initial systemic cardiovascular and renal adaptations to pregnancy in women who develop a recurrent gestational hypertensive disorder differ from those in their counterparts with an uneventful next pregnancy by smaller rises in creatinine clearance and cardiac output.