Association of neonatal respiratory distress with birth asphyxia and deficiency of red cell mass in premature infants

Effect of timing of umbilical cord clamping and other strategies to influence placental transfusion at preterm birth on maternal and infant outcomes

BACKGROUND

Infants born preterm (before 37 weeks' gestation) have poorer outcomes than infants at term, particularly if born before 32 weeks. Early cord clamping has been standard practice over many years, and enables quick transfer of the infant to neonatal care. Delayed clamping allows blood flow between the placenta, umbilical cord and baby to continue, and may aid transition. Keeping baby at the mother's side enables neonatal care with the cord intact and this, along with delayed clamping, may improve outcomes. Umbilical cord milking (UCM) is proposed for increasing placental transfusion when immediate care for the preterm baby is needed. This Cochrane Review is a further update of a review first published in 2004 and updated in 2012.

OBJECTIVES

To assess the effects on infants born at less than 37 weeks' gestation, and their mothers of: 1) delayed cord clamping (DCC) compared with early cord clamping (ECC) both with immediate neonatal care after cord clamping; 2) DCC with immediate neonatal care with cord intact compared with ECC with immediate neonatal care after cord clamping; 3) DCC with immediate neonatal care after cord clamping compared with UCM; 4) UCM compared with ECC with immediate neonatal care after cord clamping.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (10 November 2017), and reference lists of retrieved studies. We updated the search in November 2018 and added nine new trial reports to the awaiting classification section to be assessed at the next update.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing delayed with early clamping of the umbilical cord (with immediate neonatal care after cord clamping or with cord intact) and UCM for births before 37 weeks' gestation. Quasi-RCTs were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. Random-effects are used in all meta-analyses. Review authors assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

This update includes forty-eight studies, involving 5721 babies and their mothers, with data available from 40 studies involving 4884 babies and their mothers. Babies were between 24 and 36+6 weeks' gestation at birth and multiple births were included. The data are mostly from high-income countries. Delayed clamping ranged between 30 to 180 seconds, with most studies delaying for 30 to 60 seconds. Early clamping was less than 30 seconds and often immediate. UCM was mostly before cord clamping but some were milked after cord clamping. We undertook subgroup analysis by gestation and type of intervention, and sensitivity analyses by low risk of selection and attrition bias.All studies were high risk for performance bias and many were unclear for other aspects of risk of bias. Certainty of the evidence using GRADE was mostly low, mainly due to imprecision and unclear risk of bias.Delayed cord clamping (DCC) versus early cord clamping (ECC) both with immediate neonatal care after cord clamping (25 studies, 3100 babies and their mothers)DCC probably reduces the number of babies who die before discharge compared with ECC (average risk ratio (aRR) 0.73, 95% confidence interval (CI) 0.54 to 0.98, 20 studies, 2680 babies (moderate certainty)).No studies reported on 'Death or neurodevelopmental impairment' in the early years'.DCC may make little or no difference to the number of babies with severe intraventricular haemorrhage (IVH grades 3 and 4) (aRR 0.94, 95% CI 0.63 to 1.39, 10 studies, 2058 babies, low certainty) but slightly reduces the number of babies with any grade IVH (aRR 0.83, 95% CI 0.70 to 0.99, 15 studies, 2333 babies, high certainty).DCC has little or no effect on chronic lung disease (CLD) (aRR 1.04, 95% CI 0.94 to 1.14, 6 studies, 1644 babies, high certainty).Due to insufficient data, we were unable to form conclusions regarding periventricular leukomalacia (PVL) (aRR 0.58, 95% CI 0.26 to 1.30, 4 studies, 1544 babies, low certainty) or maternal blood loss of 500 mL or greater (aRR 1.14, 95% CI 0.07 to 17.63, 2 studies, 180 women, very low certainty).We identified no important heterogeneity in subgroup or sensitivity analyses.Delayed cord clamping (DCC) with immediate neonatal care with cord intact versus early cord clamping (ECC) (one study, 276 babies and their mothers)There are insufficient data to be confident in our findings, but DCC with immediate neonatal care with cord intact may reduce the number of babies who die before discharge, although the data are also compatible with a slight increase in mortality, compared with ECC (aRR 0.47, 95% CI 0.20 to 1.11, 1 study, 270 babies, low certainty). DCC may also reduce the number of babies who die or have neurodevelopmental impairment in early years (aRR 0.61, 95% CI 0.39 to 0.96, 1 study, 218 babies, low certainty). There may be little or no difference in: severe IVH; all grades IVH; PVL; CLD; maternal blood loss ≥ 500 mL, assessed as low certainty mainly due to serious imprecision.Delayed cord clamping (DCC) with immediate neonatal care after cord clamping versus umbilical cord milking (UCM) (three studies, 322 babies and their mothers) and UCM versus early cord clamping (ECC) (11 studies, 1183 babies and their mothers)There are insufficient data for reliable conclusions about the comparative effects of UCM compared with delayed or early clamping (mostly low or very low certainty).

AUTHORS' CONCLUSIONS

Delayed, rather than early, cord clamping may reduce the risk of death before discharge for babies born preterm. There is insufficient evidence to show what duration of delay is best, one or several minutes, and therefore the optimum time to clamp the umbilical cord remains unclear. Whilst the current evidence supports not clamping the cord before 30 seconds at preterm births, future trials could compare different lengths of delay. Immediate neonatal care with the cord intact requires further study, and there are insufficient data on UCM.The nine new reports awaiting further classification may alter the conclusions of the review once assessed.

Acute Neonatal Respiratory Failure

Acute respiratory failure requiring assisted ventilation is one of the most common reasons for admission to the neonatal intensive care unit. Respiratory failure is the inability to maintain either normal delivery of oxygen to the tissues or normal removal of carbon dioxide from the tissues. It occurs when there is an imbalance between the respiratory workload and ventilatory strength and endurance. Definitions are somewhat arbitrary but suggested laboratory criteria for respiratory failure include two or more of the following: PaCO₂ > 60 mmHg, PaO₂ < 50 mmHg or O₂ saturation <80 % with an FiO₂ of 1.0 and pH < 7.25 (Wen et al. 2004).

Neonatal outcome following cord clamping after onset of spontaneous respiration

BACKGROUND AND OBJECTIVE

Evolving data indicate that cord clamping (CC) beyond 30 to 60 seconds after birth is of benefit for all infants. Recent experimental data demonstrated that ventilation before CC improved cardiovascular stability by increasing pulmonary blood flow. The objective was to describe the relationship between time to CC, onset of spontaneous respirations (SR), and 24-hour neonatal outcome.

METHODS

In a rural Tanzanian hospital, trained research assistants, working in shifts, have observed every delivery (November 2009-February 2013) and recorded data including time interval from birth to SR and CC, fetal heart rate, perinatal characteristics and outcome (normal, death, admission).

RESULTS

Of 15,563 infants born, 12,780 (84.3%) initiated SR at 10.8 ± 16.7 seconds, and CC occurred at 63 ± 45 seconds after birth. Outcomes included 12,730 (99.7%) normal, 31 deaths, and 19 admitted; 11,967 were of birth weight (BW) ≥2500 g and 813 <2500 g. By logistic modeling, the risk of death/admission was consistently higher if CC occurred before SR. Infants of BW <2500 g were more likely to die or be admitted. The risk of death/admission decreased by 20% for every 10-second delay in CC after SR; this risk declined at the same rate in both BW groups.

CONCLUSIONS

Healthy self-breathing neonates are more likely to die or be admitted if CC occurs before or immediately after onset of SR. These clinical observations support the experimental findings of a smoother cardiovascular transition when CC is performed after initiation of ventilation.

Effect of timing of umbilical cord clamping and other strategies to influence placental transfusion at preterm birth on maternal and infant outcomes

BACKGROUND

Optimal timing for clamping the umbilical cord at preterm birth is unclear. Early clamping allows for immediate transfer of the infant to the neonatologist. Delaying clamping allows blood flow between the placenta, the umbilical cord and the baby to continue. The blood which transfers to the baby between birth and cord clamping is called placental transfusion. Placental transfusion may improve circulating volume at birth, which may in turn improve outcome for preterm infants.

OBJECTIVES

To assess the short- and long-term effects of early rather than delaying clamping or milking of the umbilical cord for infants born at less than 37 completed weeks' gestation, and their mothers.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (31 May 2011). We updated this search on 26 June 2012 and added the results to the awaiting classification section.

SELECTION CRITERIA

Randomised controlled trials comparing early with delayed clamping of the umbilical cord and other strategies to influence placental transfusion for births before 37 completed weeks' gestation.

DATA COLLECTION AND ANALYSIS

Three review authors assessed eligibility and trial quality.

MAIN RESULTS

Fifteen studies (738 infants) were eligible for inclusion. Participants were between 24 and 36 weeks' gestation at birth. The maximum delay in cord clamping was 180 seconds. Delaying cord clamping was associated with fewer infants requiring transfusions for anaemia (seven trials, 392 infants; risk ratio (RR) 0.61, 95% confidence interval (CI) 0.46 to 0.81), less intraventricular haemorrhage (ultrasound diagnosis all grades) 10 trials, 539 infants (RR 0.59, 95% CI 0.41 to 0.85) and lower risk for necrotising enterocolitis (five trials, 241 infants, RR 0.62, 95% CI 0.43 to 0.90) compared with immediate clamping. However, the peak bilirubin concentration was higher for infants allocated to delayed cord clamping compared with immediate clamping (seven trials, 320 infants, mean difference 15.01 mmol/L, 95% CI 5.62 to 24.40). For most other outcomes (including the primary outcomes infant death, severe (grade three to four) intraventricular haemorrhage and periventricular leukomalacia) there were no clear differences identified between groups; but for many there was incomplete reporting and wide CIs. Outcome after discharge from hospital was reported for one small study; there were no significant differences between the groups in mean Bayley II scores at age seven months (corrected for gestation at birth (58 children)).No studies reported outcomes for the women.

AUTHORS' CONCLUSIONS

Providing additional placental blood to the preterm baby by either delaying cord clamping for 30 to 120 seconds, rather than early clamping, seems to be associated with less need for transfusion, better circulatory stability, less intraventricular haemorrhage (all grades) and lower risk for necrotising enterocolitis. However, there were insufficient data for reliable conclusions about the comparative effects on any of the primary outcomes for this review.

Effect of timing of umbilical cord clamping and other strategies to influence placental transfusion at preterm birth on maternal and infant outcomes

BACKGROUND

Optimal timing for clamping the umbilical cord at preterm birth is unclear. Early clamping allows for immediate transfer of the infant to the neonatologist. Delaying clamping allows blood flow between the placenta, the umbilical cord and the baby to continue. The blood which transfers to the baby between birth and cord clamping is called placental transfusion. Placental transfusion may improve circulating volume at birth, which may in turn improve outcome for preterm infants.

OBJECTIVES

To assess the short- and long-term effects of early rather than delaying clamping or milking of the umbilical cord for infants born at less than 37 completed weeks' gestation, and their mothers.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (31 May 2011). We updated this search on 26 June 2012 and added the results to the awaiting classification section.

SELECTION CRITERIA

Randomised controlled trials comparing early with delayed clamping of the umbilical cord and other strategies to influence placental transfusion for births before 37 completed weeks' gestation.

DATA COLLECTION AND ANALYSIS

Three review authors assessed eligibility and trial quality.

MAIN RESULTS

Fifteen studies (738 infants) were eligible for inclusion. Participants were between 24 and 36 weeks' gestation at birth. The maximum delay in cord clamping was 180 seconds. Delaying cord clamping was associated with fewer infants requiring transfusions for anaemia (seven trials, 392 infants; risk ratio (RR) 0.61, 95% confidence interval (CI) 0.46 to 0.81), less intraventricular haemorrhage (ultrasound diagnosis all grades) 10 trials, 539 infants (RR 0.59, 95% CI 0.41 to 0.85) and lower risk for necrotising enterocolitis (five trials, 241 infants, RR 0.62, 95% CI 0.43 to 0.90) compared with immediate clamping. However, the peak bilirubin concentration was higher for infants allocated to delayed cord clamping compared with immediate clamping (seven trials, 320 infants, mean difference 15.01 mmol/L, 95% CI 5.62 to 24.40). For most other outcomes (including the primary outcomes infant death, severe (grade three to four) intraventricular haemorrhage and periventricular leukomalacia) there were no clear differences identified between groups; but for many there was incomplete reporting and wide CIs. Outcome after discharge from hospital was reported for one small study; there were no significant differences between the groups in mean Bayley II scores at age seven months (corrected for gestation at birth (58 children)).No studies reported outcomes for the women.

AUTHORS' CONCLUSIONS

Providing additional placental blood to the preterm baby by either delaying cord clamping for 30 to 120 seconds, rather than early clamping, seems to be associated with less need for transfusion, better circulatory stability, less intraventricular haemorrhage (all grades) and lower risk for necrotising enterocolitis. However, there were insufficient data for reliable conclusions about the comparative effects on any of the primary outcomes for this review.

THIRD STAGE PRACTICES AND THE NEONATE

The third stage of labour is defined as the period following the completed delivery of the newborn until the completed delivery of the placenta and its attached membranes. Whilst to the exhausted labouring woman this stage may be an afterthought, it is a crucial time for fetal-to-neonatal transition. Major changes in anatomy and physiology occur in both mother and baby. It has also been described as ‘potentially the most hazardous part of childbirth, largely due to the risk of postpartum haemorrhage (PPH) on placental separation. Despite this, the current management guidelines are based on an ‘eclectic combination of historical, anecdotal, philosophical and research-based factors.

Pathophysiology of Neonatal Respiratory Distress Syndrome

Neonatal respiratory distress syndrome (RDS) remains one of the major causes of neonatal mortality and morbidity despite advances in perinatal care. The initial management of infants with RDS has almost become 'too routine' with little thought about the pathophysiological processes that lead to the disease and how the clinician can use the existing therapeutic interventions to optimize care. The transition from fetus to infant involves many complex adaptations at birth; the most important is the function of the lungs as a gas exchange organ. Preterm surfactant-deficient infants are less well equipped to deal with this transition. Optimum gas exchange is achieved through matching of ventilation and perfusion. In RDS, ventilation may be affected by homogeneity of the airways with atelectasis and over distension, as hyaline membranes block small airways. In turn this contributes to the inflammation that becomes bronchopulmonary dysplasia. Exogenous surfactant given early, particularly with positive end-expiratory pressure and, where necessary, gentle ventilation, would seem to be the optimum way to prevent atelectasis. How this can be achieved in neonates after surfactant therapy is explored through a review of the normal physiology of the newborn lung and how this is affected by RDS. The therapeutic interventions of resuscitation, exogenous surfactant, ventilation and inhaled nitric oxide are discussed in relation to their effects and what are currently the optimum ways to use these. It is hoped that with a better understanding of the normal physiology in the newborn lung, and the effects of both disease and interventions on that physiology, the practising clinician will have a greater appreciation of management of preterm infants with, or at risk of, RDS.

Early versus delayed umbilical cord clamping in preterm infants

BACKGROUND

Optimal timing for clamping of the umbilical cord at birth is unclear. Early clamping allows for immediate resuscitation of the newborn. Delaying clamping may facilitate transfusion of blood between the placenta and the baby.

OBJECTIVES

To delineate the short- and long-term effects for infants born at less than 37 completed weeks' gestation, and their mothers, of early compared to delayed clamping of the umbilical cord at birth.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (2 February 2004), the Cochrane Neonatal Group trials register (2 February 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 1, 2004), PubMed (1966 to 2 February 2004) and EMBASE (1974 to 2 February 2004).

SELECTION CRITERIA

Randomized controlled trials comparing early with delayed (30 seconds or more) clamping of the umbilical cord for infants born before 37 completed weeks' gestation.

DATA COLLECTION AND ANALYSIS

Three reviewers assessed eligibility and trial quality.

MAIN RESULTS

Seven studies (297 infants) were eligible for inclusion. The maximum delay in cord clamping was 120 seconds. Delayed cord clamping was associated with a higher hematocrit four hours after birth (four trials, 134 infants; weighted mean difference 5.31, 95% confidence interval (CI) 3.42 to 7.19), fewer transfusions for anaemia (three trials, 111 infants; relative risk (RR) 2.01, 95% CI 1.24 to 3.27) or low blood pressure (two trials, 58 infants; RR 2.58, 95% CI 1.17 to 5.67) and less intraventricular haemorrhage (five trials, 225 infants; RR 1.74, 95% CI 1.08 to 2.81) than early clamping.

REVIEWERS' CONCLUSIONS

Delaying cord clamping by 30 to 120 seconds, rather than early clamping, seems to be associated with less need for transfusion and less intraventricular haemorrhage. There are no clear differences in other outcomes.

Is it possible to predict the blood volume of a sick preterm infant?

OBJECTIVE

To investigate the relation between the measured intravascular blood volume (BV) and current methods of indirectly assessing BV status in sick preterm infants on the first day of life.

METHODS

Thirty eight preterm infants of gestation 24-32 weeks (median 30) and weight 480-2060 g (median 1220) were studied. Red cell volume was measured by the fetal haemoglobin dilution method in six infants and by the biotin labelled autologous red cell dilution method in the remaining 32. Total BV was calculated by dividing red cell volume by packed cell volume. Indirect assessments of BV status using heart rate (HR), core-peripheral temperature difference, mean arterial pressure, base excess, and packed cell volume were recorded.

RESULTS

The mean (SD) initial measured BV was 71 (12) ml/kg (range 53-105). The mean HR was 148 beats/min (range 130-180), which correlated positively (r = 0.39, p = 0.02) with BV (higher HR was associated with higher BV). The mean base excess was -3.19 mmol/l (range -18 to +6.2). The negative base excess correlated significantly positively (r = 0.41, p < 0.01) with BV (more acidotic babies tended to have higher BV). There was no significant correlation between core-peripheral temperature difference, mean arterial pressure, or packed cell volume and BV. Regression analysis showed that base excess and HR were significantly related to BV; base excess alone can predict variability in BV only to 17%, and base excess with HR can predict variability in BV to 29%.

CONCLUSION

The conventional clinical and laboratory indices are poor predictors of measured blood volume.

Delayed umbilical cord clamping in preterm infants: a feasibility study

OBJECTIVES

To assess: (i) the size of placental transfusion following a 30 s delay in cord clamping following vaginal and Caesarean births; and (ii) the feasibility of delaying cord clamping in the labour ward and particularly in the operating theatre.

METHODS

Fourty-six infants born at 26-33 weeks gestation were randomized to having the umbilical cord clamped either immediately or 30 s after birth. The venous haematocrit was measured at 1 and at 4 h of age.

RESULTS

There were trends towards higher mean haematocrits in the infants following delayed clamping, but these were not significant either at 1 h (55 +/- 7.7 vs 52.9 +/- 7) or at 4 h of age (55 +/- 7 vs 52.5 +/- 7). The trends were more marked in the infants born by Caesarean section, and in those born at 26-29 weeks gestation.

CONCLUSIONS

A 30 s delay in cord clamping is feasible at both vaginal and Caesarean births, but does not lead to the predicted difference in infant haematocrit. Although physiological studies suggest that a placental transfusion of 15-20 mL/kg occurs within 30 s of delivery, these data suggest that future trials should either delay cord clamping for more than 30 s, or should alter the position of the infant in relation to the uterus in order to facilitate the transfusion. Delayed cord clamping is feasible at Caesarean section.

Randomised controlled trial of plasma protein fraction versus dopamine in hypotensive very low birthweight infants

Around 20% of very low birthweight infants admitted to a neonatal intensive care unit become hypotensive within 24 hours of their admission. Standard treatment is either expansion of the circulating volume by the infusion of plasma protein fraction or by using dopamine to improve cardiac function. The purpose of this study was to investigate by a randomised controlled trial which was the most appropriate treatment. Thirty nine infants were randomised to receive either plasma protein fraction or dopamine as first line treatment if they became hypotensive within 24 hours of admission to the neonatal intensive care unit. Seventeen of 19 (89%) infants responded to dopamine, whereas only 9/20 (45%) responded to plasma protein fraction. The median dose of dopamine needed to increase the blood pressure to at least the 10th centile was 7.5 micrograms/kg/min and was infused for a median duration of 18 hours. These observations suggest that dopamine should be used earlier in the treatment of these infants than has previously been recommended.

Umbilical cord clamping and preterm infants: a randomised trial

OBJECTIVE

To investigate the clinical effects of regulating umbilical cord clamping in preterm infants.

DESIGN

A prospective randomised study.

SETTING

The Queen Mother's Hospital, Glasgow.

SUBJECTS

36 vaginally delivered infants over 27 and under 33 weeks' gestation.

INTERVENTION

Holding the infant 20 cm below the introitus for 30 seconds before clamping the umbilical cord ("regulated" group, 17 patients), or conventional management ("random" group, 19 patients).

MAIN OUTCOME MEASURES

Initial packed cell volume, peak serum bilirubin concentrations, red cell transfusion requirements, and respiratory impairment (assessed by ventilatory requirements, arterial-alveolar oxygen tension ratio over the first day in ventilated infants, and duration of dependence on supplemental oxygen).

RESULTS

There were statistically significant differences between the two groups in mean initial packed cell volume (regulated group 0.564, random group 0.509) and median red cell transfusion requirements (regulated group zero, random group 23 ml/kg). 13 infants from each group underwent mechanical ventilation and showed significant differences in mean minimum arterial-alveolar oxygen tension ratio on the first day (regulated group 0.42, random group 0.22) and in median duration of dependence on supplemental oxygen (regulated group three days, random group 10 days). Differences in final outcome measures such as duration of supplemental oxygen dependence and red cell transfusion requirements were mediated primarily through arterial-alveolar oxygen tension ratio and also packed cell volume.

CONCLUSIONS

This intervention at preterm deliveries produces clinical and economic benefits.

Peripheral circulation in the newborn: interaction of peripheral blood flow, blood pressure, blood volume, and blood viscosity

Peripheral blood flow and systolic blood pressure (strain-gauge plethysmograph), blood volume (Evans blue) and whole blood viscosity (cone-plate viscometer) have been measured in 66 premature and full-term infants 6 to 144h of age. Blood flow and blood volume were moderately decreased in the infants with respiratory distress. Highly significant (P less than 0.001) correlations were found between blood flow and blood volume (r = 0.77), blood pressure and blood volume (r = 0.50), peripheral resistance and blood volume (r = -0.44), blood flow and blood pressure (r = 0.50), blood flow and peripheral resistance (r = -0.67), peripheral resistance and blood viscosity (r = 0.45), and blood viscosity and haematocrit (r = 0.86). There was no correlation between peripheral blood flow and blood viscosity. However, at given blood volume, peripheral blood flow decreased with increasing blood viscosity. These results indicate that in newborn infants peripheral blood flow, blood pressure and peripheral resistance are influenced by blood volume, but also depend on blood viscosity.