What meconium is, and why it is in the water

Meconium is the dark, sticky first bowel movement a baby passes. Usually it arrives in a nappy in the first day or two. Sometimes it is passed before birth, and then it colours the amniotic fluid — which is why waters can be green, brown-green or almost black instead of clear or straw-coloured.

NICE makes one observation about timing that reframes it: "meconium is more common after full term". It is not automatically a sign of distress. It is a finding that changes what the team watches for.

The definition that matters

NICE defines significant meconium in its glossary, and the wording is worth having: "dark green or black amniotic fluid that is thick or tenacious, or any meconium-stained amniotic fluid containing lumps of meconium".

Everything that is meconium-stained but not that — thin, lightly coloured, no lumps — is treated as non-significant. The distinction drives what happens to your baby afterwards, so it is a reasonable thing to ask about: was it significant or non-significant meconium?

What happens in labour

NICE asks teams to document the presence or absence of meconium as part of ongoing assessment. If it is present, the team should "consider the character of the meconium and discuss the option of transfer to obstetric-led care with the woman", explaining that meconium:

may increase the risk to the baby;
means that continuous cardiotocography monitoring may be advised;
may mean that healthcare professionals trained in advanced neonatal life support are needed as soon as the baby is born.

Note the word discuss. NICE frames transfer as an option to be talked through, and its recommendation on carrying it out begins "if the woman wishes to be transferred". If birth is imminent, NICE asks the team to weigh whether birth where you are is preferable to moving you.

The new appearance of meconium during labour is on NICE's list of findings at the hourly risk assessment that prompt transfer to obstetric-led care. So is meconium-stained fluid noted at the initial triage assessment after your waters break at term.

How common a reason for transfer it is

NICE reproduces the Birthplace in England data on why women planning birth outside an obstetric unit are transferred. Meconium staining accounted for 12.2% of transfers from home, 12.2% from freestanding midwifery units and 12.2% from alongside midwifery units — the most consistent figure in the table. Delay in labour was the largest single reason in every setting.

Those are figures from the Birthplace in England research study published in 2011, describing planned births outside obstetric units in England. They are the numbers NICE itself prints.

Monitoring your baby's heartbeat

Meconium is one of the reasons continuous electronic monitoring may be recommended, and NICE points teams to its separate guideline on fetal monitoring in labour for the decision. The HSE describes the practical options in Irish units — a handheld doppler, a Pinard stethoscope, or a CTG — and notes which can be used in water.

Continuous monitoring is an offer like any other. It restricts movement, and NICE asks teams to say so honestly rather than presenting it as neutral. If you accept it, telemetry that allows you to move may be available; if you decline it, that should be recorded and your care continued.

At the birth

The instructions NICE gives for the moment of birth are mostly instructions not to do things. In the presence of any degree of meconium, teams should not suction the baby's upper airways before the birth of the shoulders and trunk, should not suction the airways if the baby has normal respiration, heart rate and tone, and should not intubate a baby with normal respiration, heart rate and tone.

If a baby does not have normal respiration, heart rate and tone, national neonatal resuscitation guidelines are followed. A team trained in advanced neonatal life support may be present at the birth for that reason. The NHS notes that some babies need help to establish breathing straight after birth, whatever the colour of the waters.

The observations afterwards

This is where the significant and non-significant distinction bites. NICE:

After significant meconium, a healthy baby should be closely observed "within a unit with immediate access to a neonatologist", with observations at 1 and 2 hours old and then 2-hourly until 12 hours old.
After non-significant meconium, observe the baby at 1 and 2 hours old, in all birth settings.

The things being looked for are listed: a respiratory rate above 60 breaths a minute, grunting, a heart rate below 100 or above 160 beats a minute, capillary refill time above 3 seconds, a temperature of 38°C or above or 37.5°C on two occasions 15 to 30 minutes apart, oxygen saturation below 95%, or central cyanosis. Any of these means a neonatologist assesses the baby, with transfer of both of you if you are at home or in a freestanding midwifery unit.

NICE also asks that the findings be explained to you, along with what to look out for and who to talk to if you are worried.

What to do at home if your waters are green

If your waters break and the fluid is green, brown or black, ring your maternity unit and say what colour it is. The NHS's description of the stages of labour treats the colour and smell of the waters as information to report. NICE's triage list for suspected rupture of membranes at term names meconium-stained liquor as a factor that means immediate in-person review.

This is not a wait-and-see. It is a phone call, and then usually a trip in to be checked, even if you feel completely well.

What it does not mean

It does not automatically mean a caesarean, an induction, or a baby who is unwell. NICE's own framing is that meconium prompts "a full risk assessment and discussion with the woman about the option of transfer". A great many babies born through meconium-stained fluid are entirely well and go home on time.

Meconium in the Waters