Objectives: To assess how the Fetal Kidney Length (FKL) in single pregnancies between 24–34 weeks correlates with gestational age (GA) determined from the last menstrual period (LMP) and to compare this with GA estimates based on femur length.
Study Design: A prospective observational study.
Patients and Methods: In this forward-looking observational study, 330 expectant mothers between 24 and 34 weeks of gestation were examined using two-dimensional ultrasound technology.
Results: The average GA was 29 ± 3 weeks, with a range of 24 to 34 weeks. Femur length averaged 67.5 ± 6 mm, ranging from 54 to 79 mm. The lengths of the right and left kidneys, along with their average, were 33.5 ± 3 mm (range 27 to 40 mm), 34 ± 3 mm (range 27.4 to 40.6 mm), and 33.5 ± 3 mm (range 27 to 40.5 mm), respectively. The accuracy of predicting GA in the third trimester was higher with the mean kidney length (R2= 0.92) compared to femur length (R2 = 0.87). Although statistically significant, the difference in length between the right and left kidneys was minimal (0.5 mm) and deemed clinically negligible, with the left kidney being slightly larger.
Conclusion: FKL emerges as a reliable marker for use in ultrasound evaluations and prenatal visits, notably from the 24th to the 34th week of gestation. FKL is an effective predictor of the expected date of delivery (EDD).