Meconium and amniotic fluid aspiration at birth: what parents should know

Babies live in a sac of amniotic fluid (also called liquor) and practise breathing movements before birth. Aspiration means that fluid, or something in it, is breathed in towards the lungs. In UK guidance the situation that causes concern is aspiration of fluid that is stained with meconium, a dark green sticky material that is the baby's first bowel motion. The standard medical term is meconium aspiration syndrome (MAS).

Meconium is usually passed after birth. Sometimes a baby passes it before or during labour, which stains the waters green or brown. NICE says meconium is more common after full term and advises that it should still trigger a full risk assessment. Passing meconium does not by itself mean the baby is in trouble, but guidelines treat it as a signal to look more closely.

Meconium aspiration syndrome describes the breathing problems that can follow when meconium-stained fluid reaches the airways. The Norfolk and Norwich guideline describes meconium blocking the smaller airways, which can cause patchy collapse of parts of the lung, air trapping and a higher chance of a collapsed lung (pneumothorax).

According to the Norfolk and Norwich guideline, meconium-stained liquor occurs in up to 10 percent of deliveries, and approximately 2 percent of those babies develop meconium aspiration syndrome. In practice that means the large majority of babies who are born through stained fluid have no lasting problem.

NICE's guideline on intrapartum care also lists meconium aspiration syndrome, along with neonatal encephalopathy, among the most common serious problems recorded in the Birthplace in England study, which is why it receives so much attention in labour care.

If meconium is seen, the midwife will note the colour and consistency and assess the whole picture, including the baby's heart rate pattern. NICE's guideline on fetal monitoring in labour advises considering the character of the meconium alongside other risk factors and discussing the option of continuous cardiotocography (CTG) monitoring with the woman, and that the type of monitoring used is her choice.

The Norfolk and Norwich guideline defines two grades. Non-significant meconium is a large amount of fluid lightly stained by meconium. Significant meconium is dark green or black fluid that is thick or tenacious, or any meconium-stained fluid containing lumps. For significant meconium it recommends continuous external fetal monitoring, and says a member of staff trained in advanced neonatal life support should be present at delivery when there are additional signs of fetal compromise.

NICE's intrapartum guideline adds that if meconium is present in someone planning birth at home or in a midwife-led unit, the option of transfer to obstetric-led care should be discussed, because meconium may increase the risk to the baby and may mean that staff trained in advanced neonatal life support are needed as soon as the baby is born.

In the first minutes after birth the baby's breathing, heart rate and tone are assessed to decide whether any help is needed. The Norfolk and Norwich guideline says a baby who cries after birth can be assumed to have an open airway and needs no further immediate action, and that a baby who needs resuscitation should be cared for according to current national neonatal resuscitation guidance.

Skin-to-skin contact with the mother, keeping the baby warm and keeping the airway open are part of NICE's routine advice for the care of the baby straight after birth, and apply to babies who are well.

Because symptoms may be delayed, babies born through meconium-stained fluid are watched. The guideline sets out the following approach for well babies.

• Non-significant meconium staining: observations at 1 and 2 hours of age, in all birth settings.

• Significant meconium staining: observations at 1 and 2 hours and then every 2 hours until 12 hours of age.

• Mothers of babies born at home through significant meconium are advised to transfer to hospital so the baby can be observed.

• Observations include general wellbeing (tone and feeding), breathing rate, chest movements, nasal flaring, grunting, blue colour, heart rate, skin colour, capillary refill and temperature, and any abnormality is reported to a neonatologist.

A baby with signs of meconium aspiration syndrome is looked after on a neonatal unit. The Norfolk and Norwich guideline describes keeping the baby warm in a controlled environment, handling the baby as little as possible, a chest X-ray and blood tests, and antibiotics because, although meconium itself is sterile, blocked airways make infection more likely. Nutrition is started early.

Breathing support is matched to severity. For mild difficulty this may be humidified oxygen or high-flow nasal oxygen. For moderate to severe disease the baby may need a breathing tube and ventilator, with surfactant given to babies who need intubation for the condition. The guideline also describes persistent pulmonary hypertension of the newborn, a complication in which blood pressure in the lungs stays high and which is treated with careful oxygenation, inhaled nitric oxide and, rarely, referral for extracorporeal membrane oxygenation (ECMO). If there is evidence of a significant lack of oxygen around birth, cooling treatment may be considered.

The sources reviewed for this page describe the care pathway rather than long-term outcomes, so no figures for recovery are given here. What the guideline makes clear is that babies are matched to the level of intervention that fits their needs, and that most babies born through stained fluid never need more than observation.

If your baby has needed neonatal care, ask the neonatal team what follow-up they recommend and which symptoms to look out for at home. Parents who find the experience distressing can raise it with their midwife, health visitor or GP.

In the UK, the Norfolk and Norwich guideline refers to neonatal intensive care units and a children's acute transport service for babies who need specialist breathing support, which is NHS-delivered care. If you are using private maternity care, ask how a baby needing intensive care would be looked after.