27 Sep The Miracle of Surfactant and a Baby’s First Breath
By Barbara Hanrahan – Nursing sister and midwife, SA certified perinatal educator course develop and facilitator, masters in midwifery
Foetal breathing movements have been identified as early as 11 weeks gestation. These movements increase in intensity and frequency until they occur 50% of the time whilst the baby is in utero. The rate varies between 30 – 70 breaths per minute. This helps develop the pliability of the foetal lungs so that once the baby breathes in oxygen at birth, the lungs are flexible and can function adequately for independent respiration. It also strengthens the diaphragm and muscles used during respiration.
The initiation of breathing by the newborn at birth is partly due to the –
- compression of the chest during a vaginal birth and the recoil of the chest wall
- stimulation of chemoreceptors by the reduction of oxygen and the increase of carbon dioxide in the baby’s blood
- sensory stimulation on the skin at birth – touch, pressure, temperature
- stimulation of the senses from lights and noise.
Physiologically the ability to initiate breathing relies on the production of surfactant in the foetal lungs during pregnancy, from 22 weeks gestation. The amount produced increases until the baby is born. There is a surge of surfactant production at 34 weeks gestation.
The function of surfactant is to reduce the surface tension of the alveoli in the lungs so that the lungs can expand easily and prevents the alveoli from collapsing at the end of each breath.
At the first successful breath at birth surfactant thins out the alveolar membrane and increases the surface of the alveolar for gas exchange. At term the surfactant creates a single layer lining within the alveoli – and this lining acts as an air-liquid interface – which prevents the alveoli from collapsing as the baby breathes out.
The surfactant in the foetal lungs can be increased in pregnancy by giving the mother corticosteroid such as Celestone, in the instance of premature labour. The labour will be suppressed by medication to give the corticosteroids an opportunity to stimulate the surfactant production in the foetus and thus ease the breathing for a premature infant and significantly reduces the breathing problems of premature infants.
The use of natural or synthetic surfactant after the birth is a significant way of assisting premature babies to reduce the time and need for assisted ventilation. Multiple doses of natural surfactant has the greatest success rate.
At term the baby’s lungs hold 25mg/kg of pulmonary fluid which is partially expelled with chest compression during a vaginal birth. The rest of the fluid in the foetal lungs is absorbed into the lymphatic and pulmonary vessels and returned into the cardiovascular system.
Why do some babies born by caesarean section struggle to breathe?
A baby born by caesarean does not go through the chest compression and recoil that a baby born by vaginal birth does. This means it is harder for the baby to move the fluids out of the lungs so that there is sufficient alveoli space to utilize oxygen effectively. This leads to TTN – transient tachypnoea of the newborn. The baby breathes fast and shallowly using extra muscles to breathe, leading to signs such as flaring of the nostrils and chest recession. These babies emit a grunting sound when breathing out.
If a baby is born by elective / planned caesarean section, the baby may well be 38 or 39 weeks gestation and thus present with a mild immaturity in producing surfactant and this also leads to difficulty in absorbing and clearing the lung fluid at birth.
Babies who have TTN are moved to high care or NICU – to a temperature-regulated environment, with the administration of oxygen, separated from the mother – which causes high maternal anxiety and prevents the initiation of early skin to skin contact between the mother and baby. A baby with TTN cannot be fed orally until the rapid breathing subsides, so they usually have a drip established. (Babies with intravenous therapy often go onto antibiotics which means they stay in the high care or NICU for 5 to 7 days. This also delays the initiation and early stimulation of breastfeeding. The baby colonises the hospital’s organisms rather than the friendly good organisms of the mother. This challenges the early immune system. All of these factors may delay early development which assists the baby’s brain growth and neuromuscular abilities. As the baby’s TTN resolves and the baby gets stronger the early infant development can kick in.
Nature designed an incredible system – aiding lifesaving first breaths with sufficient development and pliability for the lungs to work mechanically at birth. A system that prepares babies during labour for initiation of respiration. A system that secretes surfactant enabling the alveolar in the lungs to open and close efficiently for independent gaseous exchange which supports life. A system which sets up the mother’s chest as the best place for a newborn to adjust from intrauterine life to life in our world. In this era of knowledge and science we often forget to marvel at nature’s provision and wisdom.
When a caesarean is medically or obstetrically needed, it is a lifesaving procedure for both mother and baby. However there is very little evidence available on the benefits of elective routine caesarean section as the primary choice of birthing a baby. There is an astonishing primary caesarean section rate in South Africa. Doing a caesarean to avoid possible medico legal action does not sufficiently remove the risks and possible cascade of additional interventions entailed in administering anaesthesia and major abdominal surgery.