Newborn poop blowouts: why they happen and how to handle them

What's probably happening

A blowout is poo escaping the nappy (diaper) — usually up the back, sometimes out the leg holes. It is a containment failure, not a medical event.

• Loose newborn stools meet a fit gap. Breastfed stools especially are runny by design. Any gap at the waistband or leg cuffs lets them escape upward or sideways.
• Wrong size or wrong fit. Too small means the back is exposed. Too big means slack at the legs. The waistband should sit at the navel or slightly higher, with the cuffs flared outward.
• A long stretch since the last change. A loaded nappy at the volume limit gives way at the next push.

Frequency in the first 8 weeks varies by feeding type. Breastfed babies often poo with most feeds in the first month. Formula-fed babies usually go less often. Either pattern is normal if the baby is feeding well and gaining weight.

When to escalate

See a doctor when you can:

• A clear pattern of explosive watery stools, more than 3 in 24 hours, lasting over 24 hours. Possible gastroenteritis.

Get immediate medical care:

• Blood in the stool — streaks, spots, or mixed through.
• Black tarry stool after day 4 (after meconium has cleared).
• Fewer than 5 heavy wet nappies in 24 hours after day 5, alongside frequent loose stools.
• Fever > 38°C in a baby under 3 months.