Can twin fetuses be numerically clustered characterizing fetal cardiovascular system function?

Second-trimester cardiovascular biometries in growth-restricted fetuses; a multicenter cohort study

BACKGROUND

Intrauterine growth restriction is associated with an increased risk of cardiovascular changes neonatally. However, the underlying pathways are poorly understood, and it is not clear whether the dysfunction is already present in the fetus.

OBJECTIVE

This study aimed to investigate fetal cardiac dimensions assessed from images at the second trimester anatomy scan from fetuses classified postnatally as small for gestational age and intrauterine growth restricted and compare them with appropriate for gestational age fetuses.

STUDY DESIGN

This was a substudy from The Copenhagen Baby Heart Study, a prospective, multicenter cohort study including fetuses from the second trimester of pregnancy in Copenhagen from April 2016 to October 2018. The mothers were recruited at the second trimester anatomy scan that included extended cardiovascular image documentation followed by consecutively measured heart biometries by 2 investigators blinded for the pregnancy outcome. The fetuses were classified postnatally as small for gestational age and intrauterine growth restricted according to the International Society of Ultrasound in Obstetrics and Gynecology 2020 guidelines using birthweight and with a retrospective assessment of Doppler flow. The mean differences in the cardiovascular biometries were adjusted for gestational age at the time of the second trimester scan and the abdominal circumference. The z-scores were calculated, and the comparisons were Bonferroni corrected (significance level of P<.005). Receiver operating characteristic curves were computed after performing backward regression on several maternal characteristics and biomarkers.

RESULTS

We included 8278 fetuses, with 625 (7.6%) of them being small for gestational age and 289 (3.5%) being intrauterine growth restricted. Both small for gestational age and intrauterine growth restricted fetuses had smaller heart biometries, including the diameter at the location of the aortic valve (P<.005), the ascending aorta in the 3-vessel view (P<.005), and at the location of the pulmonary valve (P<.005). The intrauterine growth restricted group had significantly smaller hearts with respect to length and width (P<.005) and smaller right and left ventricles (P<.005). After adjusting for the abdominal circumference, the differences in the aortic valve and the pulmonary valve remained significant in the intrauterine growth restricted group. Achievement of an optimal receiver operating characteristic curve included the following parameters: head circumference, abdominal circumference, femur length, gestational age, pregnancy associated plasma protein-A multiples of median, nullipara, spontaneous conception, smoking, body mass index <18.5, heart width, and pulmonary valve with an area under the curve of 0.91 (0.88-0.93) for intrauterine growth restricted cases.

CONCLUSION

Intrauterine growth restricted fetuses had smaller prenatal cardiovascular biometries, even when adjusting for abdominal circumference. Our findings support that growth restriction is already associated with altered cardiac growth at an early stage of pregnancy. The heart biometries alone did perform well as a screening test, but combined with other factors, it increased the sensitivity and specificity for intrauterine growth restriction.

Aortic pulse waveforms for evaluating cardiac performance in the human fetus

Pulse waveforms of the fetal descending aorta were obtained using an echo-tracking system to clarify the gestational age-related changes and the usefulness for detecting cardiac dysfunction. Peak systolic (PSD) and end diastolic diameter (EDD), pulse amplitude (Amp) and Amp:EDD ratio, calculated from the pulse waveforms, were adopted for analysis. In 196 normal fetuses after 20 weeks, the PSD, EDD and Amp increased, and Amp:EDD ratio decreased linearly with advancing gestation. The 19 fetuses with suspected cardiac dysfunction were divided into healthy and altered cardiac function subgroups, according to the values of fractional shortening and preload index. Of these, 7 fetuses with cardiac dysfunction had significantly higher incidence of low Amp (p < 0.01) and Amp:EDD ratio (p < 0.001) than remaining 12 fetuses with normal cardiac function. The pulse waveform analysis in the fetal descending aorta proved useful for detecting fetal cardiac dysfunction in utero.