Tracking and Determinants of Kidney Size From Fetal Life Until the Age of 2 Years: The Generation R Study

Background: An adverse fetal environment may lead to smaller kidneys and subsequently kidney disease and hypertension in adulthood. The aims of this study are to examine whether kidney size tracks from fetal life to childhood and whether maternal and fetal characteristics are associated with kidney size at the age of 2 years. Study Design: Prospective cohort study from fetal life onward. Setting & Participants: The study was conducted in a group of 688 infants in Rotterdam, The Netherlands. Entry criteria were singleton, noncomplicated pregnancies, and Dutch ethnicity. Predictors: The maternal characteristics age, height, and prepregnancy weight were measured in early pregnancy. Fetal growth, head circumference, abdominal circumference, femur length and estimated fetal weight, and placental characteristics were assessed in the second and third trimesters. Outcomes & Measurements: Kidney size, defined as length, width, depth, and volume, was measured in the third trimester of pregnancy and at postnatal ages 6 and 24 months. Results: Overall median gestational age was 40.3 weeks (95% range, 36.0 to 42.3 weeks), and mean birth weight was 3,536 +/- 524 (SD) g. Children tended to remain in the lowest and highest quartiles of kidney volume from the third trimester to the age of 2 years (odds ratio, 2.05; 95% confidence interval, 1.38 to 3.06; odds ratio, 3.29; 95% confidence interval, 2.22 to 4.87, respectively). Maternal height and prepregnancy weight were associated positively with kidney volume at the age of 2 years. Third-trimester fetal head circumference, abdominal circumference, and estimated weight and postnatal length were associated positively with kidney volume at the age of 2 years. Preferential fetal blood flow to the brain was associated with smaller kidneys. Limitations: Kidney measurements successfully performed in only 86% of children. Conclusions: Small kidney size in fetal life tends to persist in early childhood. Maternal anthropometrics and fetal biometrics and blood flow patterns are associated with kidney size in childhood. Follow-up studies are needed to examine whether these variations in kidney size are related to kidney function and blood pressure in later life.