Meconium comes from the Greek word “meconi” which means poppi juice or opium. Meconuim is composed of all the substances that have built up in the baby’s gut during pregnancy. Meconuim is a sterile compound and is mostly water (70-80% and a number of other interesting ingredients: small bile pigment, bile acids, residue of intestinal secretions, mucus glycoprotein’s, lips and proteases etc. About 15% of babies are born with meconuim stained liquor (MAS).
Meconuim stained liquor occurs when the baby inhales meconuim during labour, birth or immediately following birth. You can see a simple explanation of MAS in utero here. Many theories have been proposed to explain the passage of meconium in utero; however, the precise mechanisms remain unclear. The fetal bowel has little peristaltic action and the anal sphincter is contracted. It is thought that hypoxia and academia cause the anal sphincter to relax, whilst at the same time increasing the production of motilin, which promotes peristalsis.
Risk factors that may cause stress on the baby before birth include:
- “Aging” of the placenta if the pregnancy goes far past the due date
- Decreased oxygen to the infant while in the uterus
- Diabetes in the pregnant mother
- Difficult delivery or long labour
- High blood pressure in the pregnant mother
- Direct pushing
- Lack of antenatal care
- Cord involvement
- Natural therapies
- Early rupture of membranes
Induction of labour is a strong risk factor. We know that we see more meconium in induced babies. A logical guess may be that we see more meconium in postdates babies simply because postdates babies are far more likely to be induced than are 40 week babies.
A careful review of the recent literature indicates clearly that a policy of non-suctioning is as safe as routine suctioning at the perineum for infants born with meconium-stained amniotic fluid. Risks of intrapartum suctioning include causing the fetus to “gasp,” and causing vagal stimulation and postnatal fetal depression and / or bradycardia. Instead, the baby should be transferred quickly to the neonatal team, who will initiate management of the neonatal airways as indicated. Evidence of the effectiveness of intrapartum suctioning comes from the results of a single retrospective cohort study indicating a non-significant trend towards improved outcomes. The results of that study have been subsequently contradicted by two other studies showing equivalent outcomes with no intrapartum suctioning.
If meconium is present during labour and birth, the pregnant should be watched more closely for signs of fetal distress. Alone, meconium staining of the amniotic fluid does not mean that a baby is suffering from fetal distress. However, since it is one sign, the labour and birth team will look for others signs and continue with the pregnancy as normal as possible without causing any discomfort.
Unsworth, J., Vause, S. (2010). Meconuim in Labour. Obstetrics, Gynaecology & Reproductive Medicine, Volume 20, Issue 10, October 2010, Pages 289-294