Ultrasonographic normogram of fetal kidney circumference and fetal abdominal circumference ratio for early prenatal diagnosis.

Serial ultrasound scans were done in 300 fetuses between 16 to 24 weeks of gestation to establish the normogram of fetal kidney circumference (FKC) and fetal abdominal circumference (FAC) ratio (FKC/FAC). Of 300 fetuses, 150 fetuses were in the high risk group for fetal malformation and 150 patients were in the control group. The value of FKC/FAC varied from 0.27 to 0.30 from 16 to 24 weeks of gestation. No statistical difference was observed in the value of FKC/FAC in high risk and low risk (control) cases (p > 0.05). The value of FKC/FAC greater than or equal to 0.5 at 20 weeks or more was pathological for enlarged kidney. In 4 cases of multicystic kidney, the value of FKC/FAC ranged from 0.50 to 0.52 which was approximately 6SD above the normal mean ratio for that period of gestation.