Meconium In Amniotic Fluid – Is It Dangerous?

Meconium In Amniotic Fluid - Is It Dangerous?

Meconium present in amniotic fluid is something all pregnant women are told to look out for.

Meconium is your baby’s first ‘poo’ and is usually harmlessly passed once your baby is born.

In some cases, babies will pass this substance before birth and can potentially inhale it, causing serious complications.

Understanding what causes meconium in your amniotic fluid can help you to potentially prevent it from occurring, or to make decisions about your care if it does happen.

What Is Meconium and When Is It Dangerous?

Meconium forms as a baby swallows amniotic fluid during pregnancy.

Most of the fluid is water but there is also debris such as hair, fetal cells, mucus and so on.

This debris is left in the intestine when the water is absorbed and removed. What is left behind is a sticky, thick substance called meconium and by the time your baby reaches 40 weeks, their intestine is filled with meconium.

You can everything you need to know about meconium here.

Meconium itself is harmless and most babies can pass it while still in utero or during labour and have no problems.

If the meconium is inhaled into the lungs (meconium aspiration syndrome or MAS) it has the potential to be dangerous of even fatal to newborns.

Meconium aspiration syndrome (MAS) is a very rare complication. If the meconium enters the lungs it can cause an obstruction in the airways, resulting in breathing problems. Meconium can also cause inflammation of the lungs, leading to infections such as pneumonia.

In order for a baby to take a deep breath while in utero, he would need to be severely lacking in oxygen. There would be several signs of distress well before this happened and care providers would investigate further.

During labour, your baby’s chest is being compressed by contractions and can’t physically take a breath. Again if low oxygen was causing distress to your baby, your care provider is likely to pick it up long before your baby took a gasp.

Why Do Babies Pass Meconium?

Up to 10% of babies will pass meconium in utero, that is before they are born.

Why this happens we don’t really know but there are a number of theories:

  • The baby’s digestive system has matured and begun working. Meconium being passed before 34 weeks gestation is rare, is only slightly more likely up to 37 weeks (early full term), then increases in likelihood with each gestational week from 37 weeks.
  • Reduced oxygen (hypoxia) can cause the intestines to move and the anal phincter to relax, causing meconium to be passed. This is often thought to be a sign of distress but babies can be born with meconium and no distress and vice versa.
  • Umbilical cord compression during contractions, or compression of the head during birth, can cause what is known as a vagal response. The vagus is part of the involuntary nervous system and takes care of unconscious body responses, such as controlling the gastrointestinal flow. If the vagal response is stimulated , babies may pass meconium without signs of distress.

Most health experts would have us believe meconium alone is a sign of fetal distress, during pregnancy or during labour. But as can be seen, it can be a normal, physiological event.

What Can Cause Distress To Babies?

Reduced levels of oxygen during labour is called hypoxia. During normal labour, the umbilical cord can be compressed and slow down blood and oxygen flow to the baby. This causes the baby’s heart rate to dip during contractions, but recover to a normal rate once the contraction is complete. Babies usually cope well with this temporary reduction in blood flow.

If the heart rate doesn’t recover, it can be a sign that baby isn’t coping and further investigation is needed to find out why. Most often a change of position will resolve the issue.

However there are a number of routine procedures and situations in hospital settings that may affect blood flow and oxygen to your baby, such as:

  • Restricting movement in labour due to fetal monitoring or IV
  • Inducing or augmenting labour with artificial oxytocin
  • Artificial rupture of membranes (AROM) if the cord becomes compressed
  • Coached or purple pushing to speed up second stage
  • Clamping and cutting the cord before it has finished pulsing
  • Noisy, bright and stressful environment which interrupts the normal process of labour.

What Happens If There Is Meconium?

When care providers see evidence of meconium having been passed it causes a great deal of concern.

The most common response is to monitor the baby for other signs of distress, which is usually fetal heart rate. If it appears the baby isn’t doing well, care providers will increase interventions to make sure the baby is born as quickly as possible This could be either inducing or speeding up labour, an instrumental birth, or a c-section.

It was common practice from the 1970s to suction all babies born with any meconium in the amniotic fluid, regardless of whether they showed signs of aspiration or not. Care providers would use a bulb syringe or tube to suck out any meconium present in the baby’s lungs and airways.

Current practice guidelines such as those from the UK’s peak health body NICE, no longer recommend suctioning routinely, instead only suctioning babies which are floppy, unresponsive and need resuscitation.

After birth, babies are monitored regularly, having their temperature taken in case of infection, respiration and heart rate will be checked, in some cases bloods may be taken and possibly the baby will be in a special care nursery, separated from mum.

What Can I Do If There Is Meconium Present?

Research shows most babies who develop MAS have inhaled meconium while still in the uterus.

It’s important to be aware of how to avoid increasing the chances of your baby inhaling meconium if it is present:

  • Let labour start spontaneously, avoid labour induction and augmentation unless medically necessary, especially for post dates babies.
  • Choose the setting and care provider who will best support you to achieve an undisturbed labour. Keeping stress out of the birthplace maximises your chances of having a normal, complication free labour.
  • Unless your waters break, it is impossible to tell if your baby has passed meconium while in utero. Avoid having your amniotic sac ruptured. The amniotic fluid will keep any meconium diluted and provide plenty of cushioning to protect against compression of the cord.
  • Discuss with your care provider the type of meconium present, in consideration of your gestational dates, and any signs of fetal distress, so you can make an informed decision about necessary monitoring and interventions.
  • During the second or pushing stage, avoid coached or purple pushing as this can reduce the oxygen flow to your baby.
  • Allow your baby’s head to be born slowly and calmly while you are in an upright position, as this will encourage fluids to be pressed out of the chest and drain from the baby’s airways.
  • When the baby is completely born and is skin to skin, leave the cord intact until it stops pulsing, as the baby is receiving oxygen rich blood. Clamping and cutting also encourages the baby to inhale deeply which should be avoided.

Meconium is not dangerous unless it is inhaled by your baby, which rarely happens unless your baby is in severe distress.

It’s a good idea to discuss expected management and treatment with your care provider, so you can make an informed decision about your care. Being aware of the situations and interventions which can increase this risk can help you to avoid this potential complication as well as avoid traumatic suctioning which may not be needed.

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Sam McCulloch Dip CBEd CONTRIBUTOR

Sam McCulloch enjoyed talking so much about birth she decided to become a birth educator and doula, supporting parents in making informed choices about their birth experience. In her spare time she writes novels. She is mother to three beautiful little humans.


2 comments

  1. I gave birth through c section in sep-2016. There was one round of umbilical cord. I got pains and after trying for 10hrs for vaginal delivery baby passed stool in the womb. So doctor decided to do c-section. So here my question is, is there any chance for vaginal delivery second time and how long I should wait if I want to go for vaginal delivery.

  2. Hi,

    With my first baby, my son had meconium and the waters broke spontaneously. I went to hospital around 9 hours after the water broke.
    My son did not inhale it and later I learned that the meconium was thin.
    Now I’m pregnant with my second baby and I would like to deliver at home. The obstetrician is (kind of) against home birth and he tried to scared me saying that since I already had a baby who had meconium in the womb, it is very likely that this baby will have it as well.
    To be honest I don’t understand why that could be… but since I’m not an expert I was wondering if it’s true.

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