Re: Maternal obesity affects fetal myocardial function as early as in the first trimester. C. B. Ingul, L. Loras, E. Tegnander, S. H. Eik Nes and A. Brantberg. Ultrasound Obstet Gynecol 2016; 47: 433 442.
Ingul et al. performed a longitudinal case control study of cardiac function in fetuses of obese pregnant women (FOW) at St. Olavs Hospital, Norway. They included 52 obese and 24 normal weight pregnant women. Color tissue Doppler imaging (C TDI) derived longitudinal strain and strain rate, pulsed wave tissue Doppler indices and B mode measurements of the interventricular septal thickness were assessed at 14, 20 and 32 weeks' of gestation. The main findings of this study were reported as significantly lower strain rate and myocardial velocity values detected from 14 weeks of gestation, and significant increase in interventricular septal thickness at 32 weeks, exhibited by FOW compared with fetuses of normal weight women. Strengths of this study are the prospective follow up case control design, with sufficient number of subjects in both the study and control groups, and application of C TDI, a novel modality in fetal cardiac functional assessment, which enabled detection of myocardial dysfunction in FOW as early as 14 weeks of gestation. The prevalence of obesity, particularly in women of childbearing age, is a global health concern1. Obesity is associated with chronic low grade inflammation and oxidative stress that could extend to the placenta and expose the fetus to an inflammatory environment during development1,2. Many previous animal studies have reported that maternal obesity might cause adverse outcome in the fetal cardiovascular system, resulting in alteration in some cardiac signalling pathways that could predispose the fetus to insulin resistance, induce fibrosis in the fetal myocardium and lead to subsequent cardiac dysfunction3. Human studies have shown an important influence of maternal obesity on impairment of fetal diastolic function4 and an increased risk of premature death from cardiovascular disease in offspring of obese mothers1,5. Modern cardiac imaging modalities, such as tissue Doppler and speckle tracking imaging have changed fundamentally the way in which echocardiography approaches the analysis of global and regional myocardial function, demonstrating a higher sensitivity for detecting even mild myocardial damage compared with conventional echocardiographic techniques and an ability to detect subclinical changes in the fetal heart. The work by Ingul et al. emphasizes the role of novel ultrasound modalities that, in experienced hands, could be useful techniques for assessing fetal cardiac function; however, it also highlights the lack of standardization in image acquisition, data analysis and post processing. The authors of this study encountered various problems in application of the C TDI modality to the fetal heart, interpretation of their findings and reporting repeatability and reproducibility of their results. A number of factors could influence fetal C TDI results, including: the inherent angle dependency of this technique, the particular software algorithm used, variations in sample volume size, location of region of interest, frame rate and fetal heart rate, absence of a simultaneous electrocardiographic signal, tethering motion of adjacent segments, noise and drift artifacts, fetal movements, and use of different ultrasound machines within a single study. Moreover, the use of modern ultrasound technologies, even in the research setting, is jeopardized by considerable variability in measurements between ultrasound platforms, resulting in difficulties in comparing findings between different studies. There is also no consensus and no strict methodology regarding interpretation of the results derived by these novel ultrasound techniques for the fetal heart. Ingul et al.'s appropriately conducted repeatability and reproducibility study reporting both intraclass correlation coefficient and limits of agreement could provide important information on the reliability of fetal heart functional assessment by novel techniques. In summary, evaluation of changes in fetal cardiac function, particularly early in development, is an invaluable step in understanding the effect of maternal obesity on cardiovascular health postnatally in the offspring. Future research needs to be directed towards evaluation of all aspects of myocardial deformation in order to understand fully the adaptive fetal cardiac changes in response to the adverse effects of maternal obesity. Comprehensive protocols and standardization of software algorithms for the application of modern ultrasound techniques for fetal heart function assessment could ensure the reliability and clinical relevance of their findings.
Ultrasound in obstetrics gynecology the official journal of the International Society of Ultrasound in Obstetrics and Gynecology