The road to life: neonatal transitions to extra-uterine life
The onset of labour and birth initiates profound changes for infants. It is essential to understand these unique aspects of childbirth; doing so will equip midwives with the ability to detect deviations from expected trajectories, take appropriate actions, but most importantly support normal birth transitions. These transitions involve a complex cascade of physiological, anatomical and behavioural changes acting in concert. This article will overview essential knowledge about the early adaptive changes after birth and considers initial cardio-respiratory and metabolic responses to birth, together with how midwives can support the best possible start for infants.
Neonatal Nurse at Hamad Medical Corporation, Qatar
Midwife at Women's Hospital, HMC, Qatar
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Physiological preparations for life after birth begin in the antenatal period and include, for example: surfactant production, laying down of glycogen and brown adipose reserves. Mother-infant hormonal physiology is interconnected and maternal stresses during pregnancy and labour can have effects upon fetal and infant physiology (Buckley 2015). The onset of spontaneous labour and birth are important triggers for postnatal adaptions; recent evidence supports the idea that these events might have important lifelong effects on gene expression (epigenetic effects) and health (Dahlen et al 2013). Postnatal changes affect all organs, some of these transitions being immediate, occurring in seconds and minutes (onset of breathing, for example) whilst others are gradual, occurring over hours and days and longer time frames (glucose metabolism, renal function, skin integrity and the like).
Meg, a midwife, is caring for Jenny (a primigravida at 39 weeks gestation) who is having an elective medically indicated caesarean section for breech presentation. In her birth plan Jenny has requested delayed clamping of the umbilical cord. Meg, as Jenny's advocate, speaks to both the surgeon and paediatrician outlining her wishes beforehand; they both agree to defer cord clamping providing there are no complications. However, the breech extraction is difficult and the baby is born, pale with low tone. The surgeon immediately clamps and cuts the cord and baby is transferred to the resuscitaire for paediatric attention. Ten minutes later Meg introduces Jenny to her son and skin-to-skin contact is initiated.
IMMEDIATE TRANSITIONS: RESPIRATORY AND CARDIOVASCULAR
The most immediate and far reaching changes occur in the respiratory and cardiovascular systems; Figure 1 summarises the key points about this cascade of changes. During fetal life, the lungs mature structurally and biochemically to enable them to carry out gas exchange after birth (Bedford and Lomax 2015). The challenge at birth is to rapidly change over from reliance on placental to pulmonary gas exchange. An important precursor of this changeover is the rapid dispersion of lung fluid and lung aeration to establish functional residual capacity.
Figure 1. Early respiratory and cardiovascular transitions cascade
Fluid clearance is thought to be mainly mediated through pre- and postnatal changes in intercellular fluid movements due to ionic gradients acting under endocrinal control (van Vonderen et al 2014). The clearance of fluid from the lungs is furthered by the entry of air into the airways during the first breaths (Hooper et al 2015). However, consensus about the precise mechanisms of lung fluid clearance is deficient and a number of explanations have been advanced to explain what happens (van Vonderen et al 2014; Hooper et al 2015). It is likely that several physical and physiological effects operate in tandem to quickly clear liquid from the airways in order for pulmonary ventilation to begin.
From around 12 weeks' gestation onwards the fetus develops a pattern of regular cyclical 'breathing' movements; what role this plays in the establishment of respirations at birth is debatable (van Vonderen et al 2014). The mechanisms by which initial breaths and the establishment of regular breathing occur are not fully defined (Hooper et al 2015). However, according to Van Vonderen et al (2014) there is general agreement that it involves the integration of physical and chemo-receptor stimuli. These include changes in blood gases (particularly CO2), exposure to light, temperature changes, handling and the presence of air in the airways, which together help to initiate first breaths and the onset of regular breathing.
The functional closures of the foramen ovale, ductus arteriosus (and ductus venous) are brought about through haemodynamic changes (along pressure gradients, flow directions and volumes) and these serve to functionally separate the pulmonary and systemic circulations (Bedford and Lomax 2015). These initial changes occur due to alterations in blood oxygenation, changes in vascular resistance affecting blood pressure (such as reductions in pulmonary vascular resistance), directional blood flow changes (such as reversal of shunting through the ductus arteriosus) and the removal of the placental circulation (increasing systemic pressure). In part cardiovascular transition is further mediated by lung aeration and hormonal secretions, which effect changes in cardiac output and systemic blood pressure (Buckley 2015).
Fetal to neonatal transitions also require metabolic adaptions, particularly in relation to thermoregulation and glucose, for example. After birth the infant must maintain body temperature independently. This can pose considerable challenges in unfavourable environments and circumstances, as infants naturally lose heat; in extreme circumstances, this might compromise wellbeing (Wyllie et al 2015). To assist thermal stability, a number of physiological and behavioural mechanisms operate: for example, the consumption of brown adipose tissues to generate body heat, or remaining in close physical proximity to his/her mother (Moore et al 2012; Phillips 2013). Glucose homeostasis normally takes some hours to complete after birth and most infants make these transitions seamlessly (Bedford and Lomax 2015). However, midwives need to be cognisant of the complicating effects of hypothermia on glucose metabolism in order to ensure the infant does not become metabolically compromised.
ENSURING THE BEST POSSIBLE
Midwives generally deliver infants who are healthy and they are well placed to offer support for normal transitional events (Stark et al 2016). There are several areas where midwives can facilitate these: for example, through advocating for the onset of spontaneous labour, the optimal timing of cord clamping, supporting thermal care and skin-to-skin care in the initial hours after birth.
Clamping and cutting the umbilical cord was historically undertaken to reduce blood spillage onto the bedclothes (Johnson and Taylor 2011) and remained common practice in many settings despite a lack of evidence about its utility. However, now the timing of cord clamping has become a subject of debate (Royal College of Obstetricians and Gynaecologists [RCOG] 2015). Midwives using national policy guidance (such as National Institute for Health and Care Excellence [NICE] 2014: RCOG 2015) defer cord clamping for between one and five minutes, unless there are concerns regarding cord integrity or infant wellbeing. Postnatal placental transfusion provides a term infant with approximately 80-100 ml of blood. A Cochrane review (McDonald et al 2013) reported that there was a persistent improvement in iron stores in infants following deferred as opposed to early cord clamping, the latter group being twice as likely to be iron deficient at 3-6 months of age compared with those in the deferred group. Despite these benefits deferred cord clamping remains a practice challenge in some situations like preterm birth and caesarean section birth when other care needs might take precedence.
Sensory interactions between mother and infant commence at birth and are important mediators of attachment, physiology and behaviour (Hugill 2015). Early physical contact, especially skin-to-skin shortly after birth, can help reinforce emotional connections, physiological transitions and the establishment of breastfeeding (Widström et al 2011) and should be commended as a standard of care in all births (Phillips 2013). Such contacts will also be supportive of other important transitions: for example immunological, as the skin becomes colonised with commensal bacteria from the mother (Kong and Segre 2012).
The transitions from fetal to newborn life are complex and, though broadly agreed, the detailed physiological control mechanisms are less clear and require further study to add detail. An essential element of midwifery knowledge is to understand the normal physiological expectations of infant transitions at birth. Being equipped with this knowledge enables midwives to develop the skills to detect deviant transitions and deliver beneficial practices which support normal physiological processes.
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Buckley SJ (2015). Hormonal physiology of childbearing: evidence and implications for women, babies, and maternity care. Washington, DC: Childbirth Connection Programs, National Partnership for Women and Families.
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Wyllie J, Bruinenberg J, Roehr CC et al (2015). 'European Resuscitation Council guidelines for resuscitation 2015 Section 7. Resuscitation and support of transition of babies at birth'. Resuscitation, 95: 249-263.
REFLECTION ON THE SCENARIO
During resuscitation Meg acts as the information conduit between paediatrician and Jenny. Jenny needs information regarding her baby's condition and assurance as the minutes pass.
What information could Meg provide to Jenny to relieve her anxieties during and after those first 10 minutes of her baby's life?
Providing reassurance is not a singular event and Meg has established a relationship with Jenny that should imbue trust in Meg's explanations and reassurances. However, providing specific information at this moment in time is an important aspect of overall care. This information could include detail about the team and their roles, introductions to the team in theatre before the procedure and Meg reiterating previous explanations about expected events during the operation. We do not know for definite whether Jenny was awake during the operation, but it is likely since she holds her baby shortly afterwards, so live updates on what is happening would be helpful to her.
The opening parts of the case scenario are a good example of an empowered mother stating her desires, and effective inter-professional teams working and communication taking place. Sadly, on this occasion Jenny's plan for delayed cord clamping did not happen for her baby. Explanations and debriefing in the postnatal period by Meg could help to alleviate any remaining anxieties that Jenny had.
Consider how beneficial skin-to-skin contact is for both mother and baby in these circumstances and how well this is facilitated following a caesarean section in your unit?
The benefits of early and prolonged skin-to-skin contact at birth are well established. Evidence from a Cochrane review highlights that these benefits are also available for mothers post-caesarean who have early skin-to-skin contact. There is currently no evidence from randomised controlled trials of any differences between immediate or delayed initiation of skin-to-skin on outcomes; the 10-minute delay in this case was probably not detrimental. However, mothers who have complicated or caesarean births do not always get the opportunity at birth to initiate skin-to-skin contact. This is due to many complex organisational and team-working factors, including unit culture; these barriers can all be safely overcome as shown by those centres that ensure skin-to-skin care is a universal choice for all mothers and their babies.
What alternative strategies could have been considered in relation to clamping and cutting the cord immediately to enable the baby to gain some of the benefits of deferred cord clamping?
Based on the very limited contextual detail about the baby's condition, to our mind the surgeon was probably correct in prioritising the immediate welfare of Jenny's baby over obtaining the benefits of delayed cord clamping; this is a judgement call based on context and a holistic assessment at the time.
Some older studies with preterm infants show some benefits from leaving a longer than usual length of cord attached to the baby and 'milking' the blood into the baby's circulation. This practice should not be viewed as synonymous with delayed cord clamping and evidence about efficacy and safety is not definitive and requires further study. In this case scenario, this intervention would not reflect best evidence based practice.
In this case, an alternative approach requires consideration. Rather than cutting the cord and removing the baby from Jenny, it is possible that resuscitative interventions might have been effective while the baby was still with her and the cord uncut. This is based on the premises that:
The suitability or otherwise of this approach depends upon an evaluation of continued placental circulation providing oxygenation and supporting tissue perfusion while respiration is being established and other patient safety factors affecting the mother and baby. A merit of this method is that it might have ensured that Jenny was not separated from her baby, enabling earlier skin-skin contact, and that she was able to witness the stabilisation and resuscitation, which some research suggests can be psychologically helpful. However, it might have impeded the surgeon's work.
The best choice of strategy in this case scenario is a potentially contentious area and, given the superficial detail provided about the case, either course of action might have been judged to be the optimum practice.
Review your knowledge of the fetal circulation and be able to answer the following:
What are the major anatomical features of the fetal circulation?
What happens to these structures during birth transitions and what is their fate afterwards?
While preparing for birth, how would you set up the environment to support infant thermal transitions as well as ensuring comfort for the mother?
Are there any improvements required to ensure optimal timing of cord clamping and supporting early skin-to-skin contact in your unit?
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