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Meconium stained amniotic fluid: is this a danger?

amniotic sac birth cesarean fetal distress fetal heart rate induction interventions mas meconium pitocin purple pushing rupture of membranes

Often on Facebook, I come across posts where mothers interpret events after a cesarean birth as necessitating surgery because the baby passed meconium into the amniotic fluid, posing a life-threatening situation. Let's delve deeper into this topic and determine if meconium in the amniotic fluid truly poses a danger, and if you should be concerned.

What do the statistics tell us? Meconium in the amniotic fluid is a common occurrence—around 15-20% of babies pass meconium before birth! When something happens this frequently in nature, it's more of a variation than a complication! But why do babies pass stool before birth? There are several theories; let's explore them.

  1. The baby's digestive system matures, and bowel peristalsis begins. This theory is backed by the fact that meconium in the amniotic fluid is more common in babies born slightly later. While the occurrence of meconium in the amniotic fluid is about 10-15% around the 40th week, it increases to around 35-40% by the 40th week.

  2. During the pushing stage, the anal sphincter relaxes due to the vagus reflex. As the baby passes through the pelvis, stimulation of the vagus nerve occurs. This stimulation aids in the post-birth adaptation process and automatically relaxes the anal sphincter, resulting in the common occurrence of babies passing their first stool moments after birth.

  3. Due to pregnancy cholestasis, the baby passes stool into the amniotic fluid well before birth. Pregnancy cholestasis (excessive bile acids) is a rare but serious pregnancy complication that should not be taken lightly. Meconium in the amniotic fluid is a consequence of this disease, which can be lethal for the baby.

  4. The baby goes into a stressed state due to oxygen deprivation. If the baby is deprived of oxygen, its defense mechanisms direct oxygen-rich blood to the brain and reserve non-essential organs. This causes the muscles to relax, including the anal sphincter, allowing meconium to enter the amniotic fluid.

After revisiting these possible reasons, it becomes clear that the amniotic fluid can indeed be stained with meconium even if the baby is perfectly healthy. However, the reverse is also true—the baby can be oxygen-deprived and stressed even if the amniotic fluid is clear. Hence, the most accurate indication of the baby's condition is its pulse. Therefore, if the amniotic fluid is stained with meconium and the baby's pulse is not reassuring, then these two signs together strongly suggest that the baby is not feeling well inside your belly!

Given that one cause of meconium-stained amniotic fluid can be oxygen deprivation, I strongly recommend that if your labor starts with the rupture of membranes and you notice that the amniotic fluid is not clear but yellowish-greenish, brownish, or even blackish, you should definitely go to the hospital to have the baby's condition checked with an EFM, regardless of whether labor has started or not. However, it's important to know that if the baby's heartbeat is normal, then meconium-stained fluid alone is not a reason for immediate delivery or other interventions. Moreover, it's more reason for the birth to proceed as naturally as possible!

The meconium-stained amniotic fluid and pre-birth bowel movement have another potential danger, known as meconium aspiration syndrome, abbreviated as MAS. This is a very rare but very serious complication that occurs when the baby inhales meconium deep into their lungs either in the womb or during delivery, causing respiratory difficulties and potential infections. Fortunately, MAS is so rare that it occurs only in 2-5% of cases with meconium-stained amniotic fluid, and thank God, even if it does occur, it is fatal in only 3-5% of babies. However, if babies poop so often  - in 15-20% of cases -  before birth,  then why is it so rare for the meconium to be 'breathed in'? The explanation for this is quite obvious! Babies do NOT breathe in the womb or during birth! You might have experienced that your belly moves rhythmically at times as your growing baby practices breathing, but this is only very superficial muscle activity and far from real breathing! However, in order for the baby's defense reflexes to be overridden and for the baby to truly breathe in the meconium, there must be a very serious oxygen deficiency and very serious fetal stress, which naturally have other signs - and other contributing factors! So even in these cases, meconium-stained amniotic fluid is not the sole culprit in the development of MAS!

It's also crucial to understand as you prepare for childbirth that there's a significant difference between meconium-stained fluid and thick meconium. Meconium-stained amniotic fluid can be a slightly opaque, greenish liquid with almost dissolved stool. However, it can also be a thick, blackish ointment that can cover the baby's body and face. The latter is, of course, much more dangerous! The risk of MAS is also much lower in a vigorous, timely, healthy, normal-weight newborn than in a slightly fragile, premature baby!

In summary, just the presence of meconium in the amniotic fluid is not a cause for alarm! So, don't stress and worry unnecessarily about it. However, if there's meconium-stained amniotic fluid, go to the hospital to check the baby's condition! Nevertheless, to minimize the chance of MAS, if there was meconium in the amniotic fluid, try to ensure that the birth remains in its natural rhythm and course! It's important to know that inducing labor, rupturing the membranes, using synthetic oxytocin, purple pushing, and pushing while lying on the back—each of these factors can easily lead to fetal distress independently, thereby increasing the risk of MAS!

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