Shhh... Be Very Very Quiet

From WhattoExpect.com:

For Dad: Hearing Baby's Heartbeat

Place your ear against her tummy and you may be able to hear your little one's heart beat.

You've probably been hearing your baby's heartbeat with a Doppler at those doctor or midwife visits. But at 25 weeks pregnant you can hear that thump-thump in the comfort and privacy of your own home. If the room is very quiet, and you both are very still, you may be able to hear a very faint heartbeat when you gently press your ear against her stomach. If not, try again tomorrow. You're getting closer — plus, this gets you closer to her, too.