If you've decided to time your baby's movements, US guidance points to the start of the third trimester — around week 28. Here's where that comes from, and what UK guidance says instead.
Around 28 weeks
Count the Kicks advises beginning in the third trimester — at 28 weeks, or at 26 weeks if you're high-risk or expecting twins or more. It notes that this is what ACOG recommends.
Most people start counting around week 28, once movements have settled into a pattern you can feel every day. Movements usually keep increasing until about 32 weeks, then stay about the same (RCOG).
What UK guidance says
The NHS and RCOG don't ask you to count on a schedule. They ask you to be aware of your baby's individual pattern of movements throughout pregnancy, and to seek help immediately if movements are reduced or changed — at any stage. You can read both approaches side by side in how to count your baby's kicks.
Before you start counting
You don't need to have started counting to act on a change. Whatever week you're in, if your baby's movements slow down or feel different, contact your midwife, doctor or maternity unit straight away.
RCOG adds that if by 24 weeks you have never felt your baby move, you should contact your midwife or maternity unit.
Ask at your next appointment
If you're unsure when to start, ask at your next appointment — whoever looks after your pregnancy will know it best. ACOG's patient information says the same: your health care professional will tell you how often to count and when to get in touch.