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Pregnancy Guide·Second Trimester

Week 25: Startle Reflex

Cauliflower (~22cm crown-rump)·Last reviewed: 25 April 2026
Quick answer

At week 25, your baby's startle reflex (Moro reflex) is developing. They respond to loud sounds and bright light. According to Nuhah's pregnancy guide, your baby weighs about 756g and their nostrils are beginning to open.

Baby development at week 25

The startle reflex (Moro reflex) is developing - the baby jumps in response to sudden loud sounds. Nostrils begin to open, and the baby practises breathing movements. The spine is developing its structure and joints are forming. The baby weighs about 756g and is roughly 34.6cm from head to toe. Fat deposits continue to increase.

Your body this week

Your uterus is about the size of a football. Heartburn may worsen as the uterus pushes against the stomach. You might experience haemorrhoids due to increased blood flow and pressure. Some people notice shortness of breath as the diaphragm gets pushed upwards. The glucose tolerance test may be offered around now.

Things to do this week

1
Attend your glucose tolerance test if offered
2
Start considering your maternity leave plans
3
Continue monitoring baby movements

Frequently asked questions

What is the glucose tolerance test for?

The glucose tolerance test screens for gestational diabetes, typically offered between weeks 24-28. You fast overnight, drink a glucose solution, and have blood tests. Gestational diabetes is manageable with diet changes or medication and usually resolves after birth.

Related reading

Guides
NHS Pregnancy Appointments: The Complete Timeline

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