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What is already known about this topic? COVID-19 infection in pregnancy leads to an increase in adverse maternal outcomes. Owing to paucity of data regarding SARS-CoV-2 vaccine use in pregnancy there is uncertainty regarding safety of use and subsequent pregnancy outcomes. What does this study add? Provides an overview of the available SARS-CoV-2 vaccines, their mechanisms of action and feasibility of use in pregnancy. Summarises recommendations regarding vaccination of pregnant or lactating women. Data Availability-Data sharing is not applicable to this article as no new data were created or analyzed in this study. Acknowledgements:We would like to acknowledge Mr Mohesh K Mohan for his assistance in the illustration, Ms Cecille Laureano Asibal for her administrative support.

The helix angle configuration of the myocardium is understood to contribute to the heart function, as finite element (FE) modeling of postnatal hearts showed that altered configurations affected cardiac function and biomechanics. However, similar investigations have not been done on the fetal heart. To address this, we performed image-based FE simulations of fetal left ventricles (LV) over a range of helix angle configurations, assuming a linear variation of helix angles from epicardium to endocardium. Results showed that helix angles have substantial influence on peak myofiber stress, cardiac stroke work, myocardial deformational burden, and spatial variability of myocardial strain. A good match between LV myocardial strains from FE simulations to those measured from 4D fetal echo images could only be obtained if the transmural variation of helix angle was generally between 110 and 130°, suggesting that this was the physiological range. Experimentally discovered helix angle configurations from the literature were found to produce high peak myofiber stress, high cardiac stroke work, and a low myocardial deformational burden, but did not coincide with configurations that would optimize these characteristics. This may suggest that the fetal development of myocyte orientations depends concurrently on several factors rather than a single factor. We further found that the shape, rather than the size of the LV, determined the manner at which helix angles influenced these characteristics, as this influence changed significantly when the LV shape was varied, but not when a heart was scaled from fetal to adult size while retaining the same shape. This may suggest that biomechanical optimality would be affected during diseases that altered the geometric shape of the LV.