Accuracy of Ultrasound in Fetal Sex and Weight Determination in the 2nd & 3rd Trimester When Performed By Radiology Residents & Recent Graduates: A Cross Sectional Facility Based Study
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Date
2015-10
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Addis Ababa University
Abstract
Background: Ultrasound is one of the non invasive methods for fetal sex determination and with its introduction visualization of the fetal genitalia has become possible. Although mainly fetal sex determination is done for parental curiosity it has also some clinical implication. Accurate prenatal EFW in late pregnancy and labor is extremely useful in management of labor, aiding in decision making about instrumental delivery, trial of labor after caesarean delivery and elective Cesarean section for patients suspected of having a macrosomic fetus.
Objective: Purpose of this study was to assess the accuracy of ultrasound in fetal sex determination in 2nd & 3rd trimester & weight determination in those ≥ 38wks when it is performed by those with lesser experience and exposure
Methods: Obstetric ultrasound and ultrasound of the perineal region of the fetus was done on 600 pregnant women to detect the sex of the fetus with gestational age from 16 weeks to term. Completer data and information was available in 55o of the study. There were 20 twins in the study making the overall fetuses in the study 570. For fetal weight accuracy study 235 mothers with gestational age of ≥38weeks were included. Ultrasound results were registered on pre-prepared form at the time of examination. The sex & weight was confirmed at the expected time of delivery through a phone call to the mothers and for some by revising their medical cards.
Results: Out of 570 fetuses ultrasound was able to determine the sex for 527 (92.5%); 287 of whom were confirmed female and 240were male. Overall accuracy was 84.92%. Accuracy for females was 91.63% and for males was 92.08%. When the not sure cases are excluded and samples for which actual sex determination was done are analyzed the accuracy was found to be 92%. From the 235 samples with GA of ≥38 weeks the accuracy of ultrasound fetal weight estimation within 10% of actual birth weights was 85.5%. The mean absolute error of estimated fetal weight was 226.67gm. Ultrasound generally underestimated the birth weight. Specifically ultrasound overestimated the fetal weight in those <2500gm and underestimated in those>4000gm.
Conclusion: Ultrasound is an accurate method to determine the fetal sex in the second and third trimesters with a sensitivity of 90% and specificity of 93.2% even when it is performed by those with less experience and exposure. In conclusion EFW by ultrasound in term pregnancies using the Hadlock formula was found to have a high accuracy rate when it is performed by those with less experience and exposure. So it can be applicable to make clinical decisions even when it is done by those with less experience. The over estimation of LBW and under estimation of macrosomia found in ultrasound weight estimation should be given due attention
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Ultrasound in Fetal Sex and Weight Determination, Radiology Residents & Recent Graduates