Abstract
Delayed cord clamping (DCC) improves neurologic outcomes in preterm infants through a reduction in intraventricular hemorrhage (IVH) incidence. The mechanism behind this neuroprotective effect is not known. Infants born <28 wk gestation were recruited for longitudinal monitoring. All infants underwent 72 h of synchronized near-infrared spectroscopy (NIRS) and mean arterial blood pressure (MABP) recording within 24 h of birth. Infants with DCC were compared with control infants with immediate cord clamping (ICC), controlling for severity of illness [clinical risk index for babies (CRIB-II) score], chorioamnionitis, antenatal steroids, sedation, inotropes, and delivery mode. Autoregulatory dampening was calculated as the transfer function gain coefficient between the MABP and NIRS signals. Forty-five infants were included (DCC; n = 15, paired 2:1 with ICC controls n = 30). ICC and DCC groups were similar including gestational age (25.5 vs. 25.2 wk, P = 0.48), birth weight (852.3 vs. 816.6 g, P = 0.73), percent female (40 vs. 40%, P = 0.75), and dopamine usage (27 vs. 23%, P = 1.00). There was a significant difference in IVH incidence between the DCC and ICC groups (20 vs. 50%, P = 0.04). Mean MABP was not different (35.9 vs. 35.1 mmHg, P = 0.44). Compared with the DCC group, the ICC group had diminished autoregulatory dampening capacity (-12.96 vs. -15.06 dB, P = 0.01), which remained significant when controlling for confounders. Dampening capacity was, in turn, strongly associated with decreased risk of IVH (odds ratio = 0.14, P < 0.01). The results of this pilot study demonstrate that DCC is associated with improved dynamic cerebral autoregulatory function and may be the mechanism behind the decreased incidence of IVH. NEW & NOTEWORTHY The neuroprotective mechanism of delayed cord clamping in premature infants is unclear. Delayed cord clamping was associated with improved cerebral autoregulatory function and a marked decrease in intraventricular hemorrhage (IVH). Improved dynamic cerebral autoregulation may decrease arterial baroreceptor sensitivity, thereby reducing the risk of IVH.
Highlights
At birth, infants undergo a dramatic physiological transition, driven by the shift in respiratory function from the placenta to the lungs
In a previous study we demonstrated that delayed cord clamping (DCC) is not associated with a difference in initiation of inotropic medications or mean arterial blood pressure (MABP) [36]
The immediate cord clamping (ICC) and DCC groups were similar across many factors including gestational age (25.2 vs. 25.5 wk, P ϭ 0.48), birth weight (816.6 vs. 852.3 g, P ϭ 0.73), and percent female (40 vs. 40%, P ϭ 1.00)
Summary
Infants undergo a dramatic physiological transition, driven by the shift in respiratory function from the placenta to the lungs. There is significant pulmonary vasoconstriction; oxygenated blood returned from the placenta via the umbilical vein passes directly from the right atrium to the left atrium through a patent foramen ovale with minimal pulmonary blood flow. The sudden increase in venous capacitance leads to a significant transfusion of blood from the lowresistance placental circuit to the infant [17]. Premature clamping of the umbilical cord, before respiration has been fully established, leaves a substantial amount of circulating blood volume in the placenta and may lead to inadequate preload to the left ventricle, as pulmonary blood flow is still limited [22]. Delaying clamping of the umbilical cord provides additional time for pulmonary vascular resistance to drop and results in increased circulating blood volume
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