Is pulsating cord blood sampling a suitable and reliable method for cord gas analysis at birth?Sir,We read with interest the Commentary "Delayed cord clamping and cord gas analysis at birth" by Xodo et al 1 that easily provides the clinicians the physiological basis and the rationale for umbilical cord blood gas analysis, exploring the effect of delayed cord clamping (DCC), sampling, and analysis.The final remark, considering available evidence, 2-4 is to obtain umbilical cord blood for gas analysis from both the umbilical artery and umbilical vein from the pulsating cord immediately after birth and during DCC. We reached the same conclusion in 2014, when we performed a prospective observational study on 46 matched pairs of umbilical artery and vein blood samples from the same cord, unclamped and clamped, respectively. 5 We observed that there were no significant differences on arterial pH, PO 2 , pCO 2 , SaO 2 or hemoglobin concentration (ctHb) between the samples obtained within 90 seconds from birth and the clamped one, analyzed immediately after the previous sampling. Conversely, the venous SaO 2 , ctHb, and BE were significantly different between unclamped and clamped cord, although pH, PO 2 , and pCO 2 were comparable.According to this evidence, we validated for the first time the reliability of pulsating cord blood sampling compared with the standard clamped technique, and we proposed a modified method for blood sampling from the unclamped pulsating cord, allowing the sampling of the umbilical arterial vessels as well as the DCC, essential for placental transfusion. Xodo et al suggest obtaining the samples from unclamped cord as quickly as possible, first from the artery and then from the vein. This procedure should be performed by trained personnel in a short amount of time, in order to reduce the difference among measured values of cord blood acid-base parameters. 2 In our study the comparison between simultaneous cord gas values from unclamped and clamped cord within 90 seconds from delivery did not show relevant differences in arterial samples. 5 Umbilical arterial blood most accurately reflects fetal oxygenation and acid-base status, whereas the umbilical vein blood gas measurements better reflect maternal status and placental function. The clinician performing gas analysis should be aware that sampling from arterial unclamped cord guarantees a good reliability of results compared with the standard technique. At the same time, this procedure entails all the benefits for the fetus due to DCC, as it allows placental transfusion to the infant. 5 O RCI D Mariarosaria Di Tommaso