FACTORS INFLUENCING ACCURACY OF FOETAL WEIGHT ESTIMATION BY ULTRASONOGRAPHY- A PROSPECTIVE STUDY

Abstract

Aim: Factors influencing accuracy of foetal weight estimation by ultrasonography- A Prospective Study.

Methodology: Between January 2017 and December 2019, we studied 820 singleton pregnancies of mothers who attended our antenatal care unit in the Clinic for Obstetrics and Gynecology. We included only singleton pregnancies that were delivered within 14 days of the last sonographic scan and with a birth weight 1500 g. We excluded multiple pregnancies because of their different intrauterine growth pattern. Stillborn fetuses were also excluded. In this study we had no fetal malformations that presumably would have affected the preciseness of the biometry (i.e. gastroschisis, omphalocele, hydrocephalus).

Results: During the study period we analyzed 820 pregnancies between 23 and 42 weeks of gestational age (median 37+3), fetal birth weight ranging from 530 to 5,020 g (median 3,016 g) and maternal age ranged from 18 to 47 years (median 33 years). First we compared the accuracy of the 6 formulas. Estimations within a ±10% range of the actual birth weight varied from 54.7% (Hadlock I) to 63.5% (Hadlock II). The different size of the subgroups results from missing single parameters of the sonographic biometrical investigation. The analysis of impact of factors on the accuracy of sonographic fetal weight estimation was carried out with Hadlock II, thus including 767 fetuses and the highest percentage of estimations within the ±10% range of the actual weight. Only the time between estimation and delivery had a significant impact on the accuracy of the fetal weight estimation. Beside these results the impact of sonographic visibility on the precision of the fetal weight estimation was analyzed.

Conclusion: Fetal weight estimation is important to care for the pregnancy. It may influence the intenseness of monitoring and the time and mode of delivery. Pseudo-preciseness given by today’s PACS should be carefully used, taking into consideration the limitations of the method and mainly the time interval between prenatal weight estimation and delivery.

Keywords: Pseudo-preciseness, PACS, Sonographic visibility, Fetal weight estimation, Hadlock I