Nomogram for Foetal Kidney Length

Objective : To evaluate the application and accuracy of foetal kidney length measurement in determining the gestational age of the foetus. Design : Prospective study Methodology : Out of 70 women, 50 women who were certain of their last menstrual periods (LMP) and who had regular menstrual cycle completed the study. Serial study of foetal biometry at 2 weekly intervals between 22 weeks and 38 weeks of gestation was performed to measure foetal kidney parameters and BPD, FL, AC, head circumference (HC). Result : Foetal kidney length grows at the rate of 1.7 mm fortnightly. Kidney length predicted gestational age with better precision than the model with biometric indices of Biparietal Diameter (BPD), Abdominal Circumference (AC) and Femur Length (FL). Conclusion : The study demonstrated that by measuring kidney length, pregnancies could be dated within 9.17 days in those booking late or in those who had forgotten their last menstrual periods and presented late for booking. these methods are not reliable in third trimester of pregnancy. Even the composite gestational age prediction in the third trimester does not give with great accuracy the actual gestational age, taking into consideration the discrepancies of late trimester scan and possibility of growth retardation. Recent studies have indicated that foetal kidney length (KL) correlates well with gestational age. 1 The conclusion of these studies indicate that the foetal kidney length could be used in the gestational age estimation where the dates are uncertain or the women come for ultrasound foetal biometry dating in the third trimester itself. This study was undertaken: 1. To make a nomogram for foetal kidney length. 2. To evaluate the application and accuracy of foetal kidney length measurement in determining the gestational age of the *Lecturer; **Professor and Head of Department; Department of Obstetrics and Gynaecology, Seth G S Medical College, K E M Hospital, Parel, Mumbai, India. Introduction The accurate knowledge of gestational age is a keystone in an obstetrician's ability to successfully manage the antepartum care of a patient and is of critical importance in ante-natal test and successful planning of appropriate therapy or intervention. Failure can result in iatrogenic prematurity which is associated with increased perinatal morbidity and mortality. A number of ultrasonic parameters have been used to calculate a composite gestational age (CGA). The biparietal diameter (BPD), head circumference (HC), femur length (FL), abdominal circumference (AC), length of other long bones are the frequently used parameters for determining the gestational age. Most of these methods can predict gestational age with accuracy. However,