Myth: Meconium is always a sign of fetal distress

What is meconium?

Meconium is baby's very first poo. It's made up of skin cells, amniotic fluid and languo (the fine hair that baby is covered in in the womb) which baby swallows whilst they're in the uterus throughout pregnancy. When your waters release, sometimes there may be signs of meconium, meaning baby has pooed. This usually starts a cascade of intervention (transfer from home, CTG monitoring, induction etc) and time limits set.

What causes meconium to be passed?

• baby's gut being mature and their digestive system kicking in

• their umbilical cord or head being compressed - a natural response and not a sign of distress

• distress leading to hypoxia (lack of oxygen)

Is it always a sign of distress?

In short, no. The presence of meconium in the waters increases with gestational age. 15-20% of babies at term, and 30-40% of post-term babies will have meconium in their amniotic fluid. It's more likely in post-term babies as their digestive systems are more developed. Therefore it's important to note that not all babies with meconium present are in distress. The colour of the staining in the waters matters. Light staining is potentially less of a concern that dark thick fresh meconium.

Aside from being a potential sign of distress,which can lead to asphyxia, there is also a concern that Meconium Aspiration Syndrome (MAS) could occur. This is where baby breathes in small particles of meconium. This may result in infection or breathing problems. There is a 0.06% chance of death if there is meconium present.

How to prevent it occurring?

A longer labour increases risk of meconium being passed. A labour longer than 24 hours has a 7x higher odds of meconium stained waters than those having less than 24 hours. Induced labours are 2.6x more likely to have meconium than spontaneous labours. Obstructed labours are almost 6x more likely to have meconium. Therefore, creating environments and circumstances for a quicker, spontaneous labour with freedom of movement reduces the risk of meconium being passed significantly.

References:

1. Addisu, D., Asres, A., Gedefaw, G. et al. Prevalence of meconium stained amniotic fluid and its associated factors among women who gave birth at term in Felege Hiwot comprehensive specialized referral hospital, North West Ethiopia: a facility based cross-sectional study. BMC Pregnancy Childbirth 18, 429 (2018).

2. Midwife thinking blog: the curse of meconium stained waters - Dr Rachel Reed 2015

3. Jeffrey Unsworth, Sarah Vause - Meconium in labour. Obstetrics, Gynaecology & Reproductive Medicine Volume 20, Issue 10, 2010,