Fetal Kidney Length: A Likely Sole Index for Gestational Age Determination in Late Pregnancy and Certain Abnormalities

Abstract

Background: The Obstetric management of a pregnancy relies on the knowledge of an accurate gestational age especially in unregistered cases. Aims: The aim of this study was to sonographically evaluate the fetal kidney length as a potentially dependable direct measurement parameter, to estimate gestational age in the second and third trimesters. Patients, Materials and Methods: The study involved 236 participants with 20 to 34 weeks pregnancies, referred to the Radiology department of the University of Calabar teaching hospital for obstetric ultrasound scan, within a three-month period. The fetal kidney lengths were measured, in addition to the routine parameters, which included head circumference and femur length. The estimated gestational ages derived from the routine parameters, were correlated with the kidney and femur lengths and head circumference. The data were analyzed using SPSS version 22.0. Results: Fetal kidney length increased in direct proportion to gestational age. It had a significant positive correlation coefficient (0.982) with the estimated gestational age, similar to the head circumference and femur length. Fetal kidney lengths in millimeters were nearly equal to the estimated gestational ages in weeks, especially from the thirtieth week. Conclusion: Fetal kidney length is a viable, simple and direct method for determination of gestational age of pregnancies in the second and third trimesters. Since fetal kidney length assessment is said to remain reliable after 34 weeks, unlike the head circumference and femur length, it can serve as the sole index of gestational age assessment late in pregnancy, especially in fetal structural abnormalities.