Respiratory system becomes mature in 3rd trimester. That is critical for the infant to live outside of womb. Physicians can test the infants lung maturity prior to birth if the mother going into labor. Between 36 & 38 weeks in the pregnancy the infant is deemed stable should the mom go into labor
This actually happened to me. I developed pre-mature labor but I was at 35 weeks & the docs put me on bed rest for another 2 weeks so my daughter could be born safely with no fear of respiratory failure. She was delivered fine & she 23 years old now.
