Intrauterine growth restriction is accompanied by decreased renal volume in the human fetus

OBJECTIVE: Intrauterine growth-restricted fetuses are at risk for the development of adult hypertension and related cardiovascular diseases. Congenital oligonephropathy has been postulated as the primary mechanism. The objective of our study was to determine whether ultrasonically obtained in utero measurements of renal volume or renal artery Doppler blood flow differ between fetuses that are intrauterine growth restricted and fetuses that are not. STUDY DESIGN: The study population consisted of women who were referred for a prenatal ultrasound evaluation at a large community medical center. The women were divided into two groups: women with fetal biometry that was consistent with intrauterine growth restriction and women with biometry within normal range. Information was collected on maternal demographics and other factors known to affect fetal growth. We performed detailed fetal renal anthropomorphic and Doppler blood flow measurements in addition to standard fetal biometric measurements on all patients, specifically comparing renal volume and renal artery flow data between the two groups. RESULTS: No differences were observed in maternal age, race, parity, or fetal gestational age. Renal volume in the intrauterine growth-restricted fetuses was 31% (95% CI, 20%-40%), which was less than that in the group of fetuses that were not intrauterine growth restricted after an adjustment was made for gestational age. The ratio of renal volume to estimated fetal weight was 15% (95% CI, 1%-26%), which was less than the same ratio in the fetuses that were not intrauterine growth restricted. There were no differences seen in the renal artery Doppler measurements. CONCLUSION: Intrauterine growth restriction appears to be associated with a decrease in fetal renal volume. Because renal volume is a likely proxy for nephron number, this study supports the hypothesis that intrauterine growth restriction may be linked to congenital oligonephropathy and potentially to hypertension in later life.