Yes it can be very dangerous if the baby swallows meconium. My grandson ingested his and for the first five days of life he was in nicu. He almost didn't live. And he was still having issues at 2 month check up. Now he seems to be doing much better, at 6 months.
If your water breaks in the hospital they will see the meconium in it. If it gets into the lungs it can cause breathing problems. Also can cause infections.
How or would you know if it's expelled before birth? Isn't it dangerous if they swallow it?
I believe meconium can be in fetus at 21 weeks but is usually expelled after birth. If meconium is present before birth a neonatalogist made need to be present at delivery becausevof breathing concerns. This happened with my first which is why I'm opposed to castor oil as a means of inducing labor.