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Fetoscopic myelomeningocele (MMC) repair is performed using intrauterine carbon dioxide (CO ) insufflation. Sheep experiments have shown that CO insufflation is associated with significant fetal acidemia; however, corresponding data for human pregnancy are not available. We performed umbilical venous cord blood sampling in three patients during fetoscopic MMC repair at 25 + 1, 25 + 3 and 24 + 0 weeks' gestation, respectively. Fetal venous pH at the beginning of CO insufflation was 7.36, 7.46 and 7.37, respectively in the three fetuses, and repeat values were 7.28, 7.35 and 7.36 after 181, 159 and 149 min, respectively. The partial pressure of oxygen and CO was maintained in the normal range during these times, and pH decrease was less in Patient 3 who received humidified CO insufflation. Our observations suggest that, in contrast to sheep experiments, CO insufflation during fetoscopic myelomeningocele repair does not cause acidemia in human fetuses. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

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The ductus venosus has a central role in the distribution of highly oxygenated umbilical venous blood to the heart. Its waveform is related to the pressurevolume changes in the cardiac atria and it is therefore important in the monitoring of any fetal condition that may affect forward cardiac function. The cardiovascular parameters that can influence forward cardiac function include afterload, myocardial performance and preload. Decreased forward flow during atrial systole (a-wave) is the most sensitive and ubiquitous finding when any of these parameters is affected. In contrast, decreased forward velocities during end-systolic relaxation (v-wave) are more specifically related to myocardial performance. The ductus venosus pulsatility index alone does not accurately reflect cardiac function, and in cases of suspected fetal cardiac dysfunction, echocardiography is required to identify the underlying mechanism. The role of ductus venosus Doppler in the assessment of fetal growth restriction, supraventricular tachycardia, fetal hydrops, complicated monochorionic twins and congenital heart disease is discussed with these considerations in mind.Abbreviations: AV, atrio-ventricular; CHD, congenital heart disease; DV, ductus venosus; FGR, fetal growth restriction; PIV, pulsatility index for veins; SVT, supraventricular tachycardia; TTTS, twin-to-twin transfusion syndrome. The central role of ductus venosus in fetal cardiovascular assessmentDoppler examination of the fetal venous circulation was introduced into perinatal medicine over 25 years ago to extend cardiovascular functional assessment beyond the capabilities of arterial Doppler. All central and precordial venous vessels share the same flow pattern of forward flow in ventricular systole and diastole and a temporary decrease in forward flow during end-ventricular systole and atrial systole. However, the ductus venosus (DV) has several important characteristics that favor its widespread use in fetal medicine. It is a short vessel with a relatively fixed position, allowing for standardization of the Key messageThe ductus venosus waveform reflects the pressurevolume changes in the heart. Despite the limited specificity of the ductus venosus waveform, its correlation with cardiac forward function makes it of central importance in assessing the overall severity of fetal cardiovascular pathology. Ductus venosus Doppler study has a critical role in directing the clinical management of fetuses at risk of cardiovascular deterioration.ª