In fact, it is extremely important that we do early fetal heart evaluations in women who are obese, because the risk of having a fetus with CHD is increasingly being found to be higher in obese women, and because fetal heart assessment with transvaginal ultrasound is an option only in early gestation, when the fetal heart is within the depth of penetration of the vaginal probe. With advancing gestational age, a combined abdominal/transvaginal approach becomes increasingly difficult. Our study also demonstrated a dose-response relationship between maternal obesity and CHD risk.
Preexisting diabetes mellitus, which can occur in conjunction with obesity, has been found to increase the risk for all types of CHDs, especially conotruncal abnormalities. While the pathophysiology is not completely understood, elevated oxidative stress is believed to be the primary trigger.7
First-trimester echocardiography benefits
Patients referred to our fetal heart program for detailed first-trimester fetal heart evaluation – again, a significant number of whom have been found on standard 2-D ultrasound to have increased nuchal translucency thickness or other abnormalities – undergo a four-dimensional fetal echocardiographic technique that utilizes spatiotemporal image correlation and tomographic ultrasound imaging display (STIC-TUI echo) along with color Doppler. The heart is swept from top to bottom in about 10 seconds, and tomographic ultrasound imaging is used offline, after the patient leaves, to develop volume datasets that simultaneously display multiple cross-sectional images.
This method has been implemented into our routine scan at the first trimester as well, and all of our staff have been trained to perform it. Obtaining STIC-TUI by color Doppler allows us to assess all of the important landmarks of the cardiac anatomy in one picture.
a) Identification of the four-chamber view. b) 4-D volume acquisition with STIC and color Doppler imaging. c) TUI analysis (offline) with four-chamber view as starting plane.
In a prospective study of 164 fetuses from 152 patients, we found that first-trimester STIC-TUI echo had 91% sensitivity and 100% specificity for the detection of CHD. Most anomalies were evident in the four-chamber view plane of the TUI display, and the rest were diagnosed in the outflow tract planes. Two cases of CHD missed by this first-trimester evaluation were diagnosed on second-trimester echo and neither involved a major CHD.8
Dr. Turan is associate professor of obstetrics, gynecology, and reproductive sciences, and director of the fetal heart program at the University of Maryland, Baltimore.
References
1. J Ultrasound Med. 2019 May;38(5):1269-77.
2. Prenat Diagn. 2005 Mar;25(3):253-60.
3. J Perinat Med. 2018 May 24;46(4):373-8.
4. Ultrasound Obstet Gynecol. 2015 Jun;45(6):631-8.
5. National Congenital Heart Disease Audit Report 2013-2016.
6. Pediatrics. 2015. doi: 10.1542/peds.2014-3783.