Your baby does not breathe air in the womb — oxygen comes from the placenta. But from as early as 10 weeks, your baby makes rhythmic breathing movements and swallows amniotic fluid, practising the skills they will need at birth.
Practice Breathing Movements
Fetal breathing movements are detectable on ultrasound from about 10 weeks. The baby's chest wall and diaphragm expand and contract rhythmically, drawing amniotic fluid in and out of the developing airways. These movements are not for gas exchange — they are exercise for the respiratory muscles and a mechanical stimulus that promotes lung growth.
| Stage | Breathing Milestone |
|---|---|
| 10–12 weeks | First breathing movements visible on ultrasound |
| 16–20 weeks | Increasing frequency and regularity |
| 24–28 weeks | Breathing moves for 40–80% of the time |
| 32–36 weeks | Surfactant production rises; breathing practice intensifies |
| 36–40 weeks | Final lung maturation; baby ready for air breathing |
Swallowing and the Gut
From about 11 weeks, your baby actively swallows amniotic fluid. By the third trimester, the baby swallows up to 500 mL per day. This fluid is absorbed through the gut wall, contributing to blood volume and fluid balance. The act of swallowing also exercises the digestive system and introduces flavour molecules from the mother's diet.
What Happens If the Baby Stops Breathing in the Womb?
Absence of fetal breathing movements for a prolonged period — especially combined with reduced fetal movement and low amniotic fluid — is a sign of fetal distress. The biophysical profile score used by obstetricians specifically includes breathing movements as one of five variables.
Warning
If you notice your baby is not moving and your next scan shows absent breathing movements, this is a medical urgency. Do not delay.
Can Babies Get Reflux in the Womb?
Gastro-oesophageal reflux does not occur in the womb because the sphincter tone, gravity, and amniotic fluid all prevent acid from rising. True infant reflux begins after birth when the baby is upright and swallowing air along with milk.