Until recently, clamping of the umbilical cord was done a few seconds after birth. This was based on the rationale that early interruption of foetal circulation would be beneficial to the newborn by helping prevent complications such as polycythaemia, hyperviscosity, hyperbilirubinaemia, or transient tachypnoea.1,2 Likewise, early clamping has been recommended for certain situations, such as multiple births, to prevent twin-to-twin transfusion syndrome, and in children of HIV-positive mothers to minimise the risk of transmission.2,3

At present, there is a tendency to recommend increasingly delayed clamping of the cord, on average 2–3min after birth, and in some cases until the cord has ceased pulsating, after delivery.4,5 This shift is due to the multiple benefits that this practise can afford: higher haemoglobin and haematocrit levels, increased iron stores, and earlier and longer mother–child contact.6–9 It has been described that in preterm babies this practise also reduces the risk of intraventricular haemorrhage.10–13

Under normal conditions, the blood volume of the foetus is around 70ml/kg and the placenta contains about 45ml/kg of foetal blood. When clamping of the cord is delayed, approximately 20–35ml/kg of blood can be transfused to the newborn, increasing the foetal blood volume by up to 50%.14 This additional supply of red blood cells would also increase the iron reserves of the neonate by 30–50mg, reducing the risk of iron-deficiency anaemia in the first year of life. 15,16

Despite the published data, there is no global consensus on the ideal clamping time, and even on a European level, the health protocols and policies across different countries have not reached an agreement on this issue.17 However, a trend is starting to materialise in the current recommendations for neonatal resuscitation, which stipulate a delay in cord clamping of at least one minute for uncompromised babies.18,19

Lastly, this debate has led to an increasing number of studies20–27 focused on determining the optimal timing for shutting down foeto-placental circulation and the advantages and/or disadvantages of delaying clamping of the umbilical cord.

The aim of this study was to assess the effects of early clamping (<60s) and delayed clamping (between 1–2 and 2–3min) in at-term neonates born at the Fundació Hospital Sant Jaume d’Olot, evaluating potential differences in haemoglobin, haematocrit, and ferritin levels at 48h of age, and the correlation of these levels with neonatal complications such as polycythaemia, hyperbilirubinaemia, respiratory distress syndrome, or admission to the neonatal intensive care unit.

A total of 449 live births occurred between May 2009 and May 2010, and 242 of these newborns were included in the study. They were distributed into groups as follows: 80 (33%) in Group 1 (<60s), 31 (12.8%) in Group 2 (1–2min) and 131 (54%) in Group 3 (2–3min).

Table 1 contains the main data and characteristics of the mothers. Breastfeeding was the mode of feeding practised by practically all mothers (95.4%). The prevalence of tobacco use during gestation was low, 8.6% of the mothers. Iron supplement intake and ferritin and haemoglobin concentrations in the mother during the third trimester of gestation were similar across the sample. We found no significant differences between the three groups when we analysed these variables.

Normal deliveries were most frequent, accounting for 65% of the sample (157 births), followed by caesarean deliveries (48 births, 19.8%) and instrumental deliveries (37 births, 15.2%). The average gestational age was 39 weeks and the sex distribution was 122 boys and 120 girls.

The median weight, length, and head circumference at birth were similar in all groups. The average Apgar score was similar in the 3 groups, but the score's minimum values were lower in the early clamping groups (see Table 2).

The results of cord blood analysis (Table 3) showed that haemoglobin and haematocrit levels were documented for every participant, and that there were no statistically significant differences between the three groups. On the other hand, cord blood ferritin values were documented in 230 of the 242 participants, and showed a significant difference in the median of Group 3, which was greater than the medians of Group 1 and Group 2.

The analysis performed at 48h after birth showed higher levels of haemoglobin, haematocrit and ferritin in group 3, and this difference was statistically significant. Data on haemoglobin and haematocrit levels were available for 100% of the sample, and data on ferritin for 91% of the sample.

The bilirubin levels at 48h (documented in 224 of the 242 participants) showed no significant differences between the 3 groups.

The median weight of patients at 48h after birth was similar in all groups. The hospital stay was significantly shorter in patients in Group 2 and Group 3 compared to patients in Group 1 (which included all neonates delivered by caesarean section).

Table 4 shows the statistical analysis of variables pertaining to neonatal complications. We found no significant differences in these variables with the exception of polycythaemia, of which there was a significantly higher percentage of cases in patients from the late clamping group.

The main objective of this prospective study was to assess the correlation between different timings for clamping the cord and certain neonatal complications associated to the volume of blood in the newborn. In this regard, our results only showed a significant difference for polycythaemia. We found no differences in the remaining variables (jaundice requiring phototherapy, respiratory distress syndrome, and admission to the neonatal intensive care unit). Furthermore, when we analysed the cases of polycythaemia, we found that all of them were asymptomatic and none required any treatment or specific care other than doing the test again to see whether the levels had normalised. Based on these results, we can say that clamping the cord between 0 and 3min is a safe practise that does not lead to increased morbidity.

We set arbitrary time intervals for each group (<60s, 1–2min, and 2–3min), as no clear recommendations existed at the beginning of this study. Later on, official guidelines for neonatal resuscitation were published that recommended the cord be clamped after the first 60s of life in healthy newborns. In addition, one of the most recent literature reviews (of 15 studies comprising 3911 infants)22 also defined early clamping as clamping performed within the first 60s of life. For these reasons, we believe that the time intervals we established were appropriate.

Although our study had a small sample and a short duration, both sufficed to obtain statistical results with adequate power. Likewise, the samples are comparable in every aspect under study, with the exception of type of delivery, as we had expected. Complicated deliveries prevailed in Group 1 (early clamping) because this group included all the caesarean deliveries, in which clamping has been and continues to be done within the first minute of life. The analysis of the “length of hospital stay” also showed a statistically significant greater number of days in the early clamping group for the same reason (caesarean sections).

We should also note the difference in the number of newborns included in each group. The late clamping group included over half of the sample. This may be due to the fact that our hospital is accredited for assisting natural deliveries and has a different philosophy that affects how certain decisions are made.

The results of the cord blood analysis showed significantly higher ferritin levels in the late clamping group, which is probably due to the increased volume of placental transfusion. It must be taken into account that there were no significant differences in the mothers’ ferritin levels.

In the second blood sample taken at 48h we found statistically significant differences in haemoglobin, haematocrit, and ferritin levels, with higher levels the longer clamping was delayed. The differences in the levels of haemoglobin and haematocrit were observed in clamping performed as early as minute one (Group 2), and significant differences in ferritin were observed starting at minute 2 (Group 3). These results are consistent with those of other published studies, and support the notion that newborns in whom clamping is delayed start out with a greater red blood cell mass, higher haemoglobin concentrations, and fuller iron stores, better preparing them for infancy.

It is also worth noting that, contrary to what we expected to find, the levels of bilirubin were similar in all 3 groups.

We should also underscore the exclusion criteria in our study, and that there are some patient subsets at greater risk of polycythaemia (those with intrauterine growth restriction, severe placental insufficiency, or born large for gestational age). Therefore clear and safe protocols are needed to perform clamping at the best possible time depending on the specific circumstances.

Based on the results of this study, consistent with those of other publications, we conclude that the rate of clinical complications in newborns does not increase in relation to the different timings of cord clamping. Although we found statistically significant differences in the prevalence of polycythaemia (there were more cases in the late clamping group), the higher prevalence did not lead to the establishment of any special treatment nor any appreciable clinical changes.

We can also conclude that newborns in whom cord clamping was delayed had statistically significant higher levels of haematocrit, haemoglobin, and ferritin at 48h. This may entail a better iron status in the newborn, which may be beneficial throughout infancy and therefore to the newborn's future.

The authors have no conflicts of interest to declare.