Assessing the Risks of Meconium-Stained Liquor
Published: 19 January 2020
Published: 19 January 2020
The appearance of meconium-stained liquor during labour is generally considered to be a sign of hypoxia and a predictor of poor fetal outcome. But is this always true?
Statistics for the presence of meconium-stained amniotic fluid vary greatly between 5% to 25% (Hirani et al. 2015). Or as Qadir et al. (2016) suggests between 1 to 18%. Yet regardless of these variable statistics, the significance of meconium in the amniotic fluid itself is also a widely debated subject.
Traditionally meconium has been considered a sign of fetal distress due to hypoxia but as Gupta et al. (2017) point out, as well as being a potential warning of fetal asphyxia, it can also simply be a physiological response of a normally maturing gastrointestinal tract, causing no ill effects on the fetus at all.
Reed (2015) suggests that there are three reasons why the fetus may pass meconium before birth:
It’s worth pointing out however, that fetal distress can be present without the presence of meconium, and meconium can be present without fetal distress.
Broadly speaking there are two classifications of meconium-stained liquor (MSL), non-significant and significant.
Additional indicators of a potentially adverse neonatal outcome include MSL associated with an abnormal cardiotocograph (CTG) which is more likely to result in caesarean section and potential neonatal complications (Priyadharshini 2013).
That said, it’s always important to consider the whole clinical picture before deciding if the presence of meconium is a significant finding or not.
Whilst it’s true that the presence of meconium in the amniotic fluid can be a potentially serious sign of fetal compromise, associated with poor perinatal outcome (Vaghela et al. 2014), it’s also true that most babies who are born in poor condition do not have meconium-stained liquor and most babies with meconium-stained liquor are born in good condition (Reed 2015).
In a global sense, MAS is still considered to be a marker for adverse perinatal outcomes. Whilst the passage of meconium alone is rarely a sign of significant fetal hypoxia or acidosis, meconium in the presence of an abnormal fetal heart rate (FHR) pattern should always be investigated further.
As Qadir et al. (2016) suggest the presence of thick meconium is associated with an increase in perinatal morbidity and mortality and its presence should never be overlooked.
Statistics on the incidence of MAS vary slightly from area to area but according to the Royal Berkshire NHS Foundation Trust (2017), it occurs in 1.3 out of every 1000 live-born infants and is more common in the post-term fetus.
Overall MAS is known to have a higher incidence with:
(Hirani et al. 2015)
The presence of ‘thin’ or ‘non-significant’ meconium-stained amniotic fluid (MSAF) is considered by some practitioners as ‘low risk’, requiring only intermittent auscultation instead of continuous electronic fetal heart rate monitoring (Bolten and Chandraharan 2019).
Factors associated with high risks of fetal harm include:
Whilst each hospital will have their own documented policies on the management of meconium-stained liquor, Reed (2015) urges all practitioners to consider the holistic picture and suggests the following practical steps that might help lower the risk of meconium aspiration syndrome:
Better Safer Care (2018) also comment on the following areas of uncertainty in clinical practice suggesting that:
Perhaps more controversially Reed (2015) also suggests that many of the interventions implemented due to the presence of meconium are more likely to cause complications than the meconium itself.
For example, typical responses to meconium-stained liquor include CTG monitoring with a reduction in mobility and tightened time limits for labour, all of which could make induction, augmentation or caesarean section more likely.
Hudson (2015) takes a similar view emphasising the need to avoid stimulating babies born through MSL to avoid aspiration. Delayed cord clamping is also suggested as early clamping and cutting of the cord leaves the baby with no choice but to inhale.
MAS rarely develops in infants born through meconium-stained liquor with APGAR scores of 8 or more and in the view of van Ierland, de Boer and de Beaufort (2010), these infants can be safely discharged from hospital shortly after birth.
However, assessing the risk of developing MAS doesn’t stop at delivery and most units will have a policy of extended postnatal observation for the first few hours of life.
Anne is a freelance lecturer and medical writer at Mind Body Ink. She is a former midwife and nurse teacher with over 25 years’ experience working in the fields of healthcare, stress management and medical hypnosis. Her background includes working as a hospital midwife, Critical Care nurse, lecturer in Neonatal Intensive Care, and as a Clinical Nurse Specialist for a company making life support equipment. Anne has also studied many forms of complementary medicine and has extensive experience in the field of clinical hypnosis. She has a special interest in integrating complementary medicine into conventional healthcare settings and is currently an Associate Tutor, lecturing in Health Coaching and Medical Hypnosis at Exeter University in the UK. As a former Midwife, Anne has a natural passion for writing about fertility, pregnancy, birthing and baby care. Her recent publications include The Health Factor, Coach Yourself To Better Health and Positive Thinking For Kids. You can read more about her work at www.MindBodyInk.com. See Educator Profile