Determination of Gestational Age by Tibial Length using Ultrasound in A Nigerian Tertiary Hospital

BACKGROUND: Determining fetal gestational age accurately is important to good obstetric care and outcome. Methods like measurement of symphysio-fundal height have been used but not accurate. With the advent of ultrasound, various fetal biometric parameters e.g. BPD, FKL, and fetal limbs are now being used. AIMS AND OBJECTIVES: The aim of this study is to ultrasonographically evaluate the usefulness of fetal tibial lengths as an alternate to femur lengths in predicting gestational age from the second to third trimesters. MATERIAL AND METHODS: A total of 500 pregnant Nigerian women between the GA of 13 to 41 week had ultrasound scan evaluation done at the fetal assessment unit of a Teaching Hospital. Fetal biometric parameters BPD, FL, and TL were measured and recorded against the calculated gestational age from the last menstrual periods. RESULTS: There was a strong relationship between TL and EGA with a significant positive linear correlation (r= 0.915 P<0.05). For FL, r= 0.900 and for BPD r=0.906, all related to GA. The study has also shown a good correlation between TL and the other measured variables. For TL and FL, r=0.889 while TL and BPD r=0.867, making TL a substitute limb for limb measurement and as a pointer to a skeletal anomaly or delayed bone growth or dwarfs. The mean TL ranged from 13.47 mm at 13 week to 74.64 mm at 41 weeks of gestation. CONCLUSION: This study has been able to justify the tibia as an important substitute for femur in the prediction of GA especially where the femur is susceptible to errors.