Fetal heart biventricular diameter/foot length index as a diagnostic marker of fetal macrosomia in the second and third trimester of pregnancy.

Purpose: Fetal macrosomia may have serious effects on both mother and newborn, so it is important to correctly evaluate the fetal weight before delivery. Fetal routine biometry, height of the fundus of uterus, interventricular septal thickness seems to be very good but still not perfect. In our study the relation between fetal biventricular (AP) diameter and fetal foot length was elaborated in the 2nd and 3rd trimester of pregnancy.

Material And Methods: The analyzed group ( = 423 fetuses) was divided into 2 subgroups: a control group ( = 109 fetuses) with normal biometry, normal heart anatomy and normal cardiac function, no extracardiac malformation, no extracardiac anomalies, gestational age ranged from 17.5 to 37.1 weeks of gestation, born at term with birth weight 3000-3600 g, and a study group ( = 314 fetuses) with gestational age 17.5-39.5 weeks. Among the study group there were 20 patients ( = 20 fetuses) with macrosomia defined as a neonatal birth weight of greater than or equal to 4000 g. The control group was used to generate normograms on fetal AP, foot length and AP/Foot Index. The Statistica 13.3 and Excel 365 software were used to calculate the sensitivity, specificity, positive predictive value and negative predictive values.

Results: In control group, the mean biventricular fetal heart (AP) measurement was 23 mm (12.9 mm-38 mm), the mean foot length was 43 mm (24 mm-71 mm), and the mean AP/Foot Index was 0.52 (0.40-0.65). The value of the AP/Foot Index in the second trimester of the control group was 0.53, whereas the AP/Foot Index in the third trimester of pregnancy was 0.51. The use of standard fetal biometry resulted in the prediction of macrosomia in 20%, whereas the AP/Foot index in addition to standard fetal biometry enabled the detection of 65% of macrosomia.

Conclusions: The AP/Foot Index higher than 0.52 has greater sensitivity and negative predictive value to detect macrosomia compared to standard ultrasound fetal biometry.