(836) Ultrasonographic fetal lung texture analysis in twin and singleton gestations

The objective of this study was to determine whether fetal lung ultrasound heterogeneity index (HI) differs between twin and singleton gestations during the late second and third trimesters.

Study Design: This prospective cohort study included women with singleton and twin gestations who had scheduled medically indicated ultrasound examinations at 24 weeks gestation or later in a large healthcare system from 2017 through June 2023. Grayscale fetal lung images were acquired with Voluson E8 and E10 ultrasound machines (GE Healthcare, Milwaukee, WI) using convex array transducers with a frequency range of 3-7.5 MHz. A region of interest was selected in each fetal lung image with a transverse view at the level of the 4-chamber heart excluding areas with shadow. HI was determined with MATLAB software (The Math Works, Inc, Natick, MA). This program converts the intensity of each pixel to a binary 1 (white) and 0 (black), and then calculates the percentage of white pixels with respect of the total number of pixels. Ineligible patients included those with fetal malformations and screening tests suggestive of aneuploidy. Exclusion criteria included low image quality.

Results:

During the study period, lung images were analyzed from 240 twin fetuses and 425 singleton fetuses. In total 2,151 images were analyzed. The fetal lung HI was determined for each collected image. The mean HI at each gestational week was compared between singleton and twin fetuses with two sample t-tests. Fetal lung HI throughout gestation for both groups are shown in Figure 1. There is a statistically significant divergence in mean HI beginning at 35 weeks gestational age between singleton and twin fetuses such that HI sharply increases in singleton fetuses. 

Conclusion:

A significant divergence in HI was observed between twin and singleton fetuses at and beyond 35 weeks of gestation. This finding may reflect previously reported differences in fetal lung maturity between twins and singletons during these gestational ages.