When does a unborn child start producing s meconium in the womb?

End of 1st trimester: The unborn fetus begins to accumulate meconium beginning at 12-16 weeks gestation until birth. The unborn baby does not normally excrete meconium stools while in the womb. Such passage is often a signal of fetal distress. Meconium is formed from swallowed amnionic fluid, intestinal secretions such as bile, & cellular debris. It can continue to accumulate throughout fetal development.