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Baby Development By Trimester

From when you can hear your baby’s heartbeat to what her first movements feel like, here’s how your baby develops in each trimester.

by: Sydney Loney

ondering what your baby is up to in your belly? We asked world-renowned radiologists, Drs. Peter Doubilet and Carol Benson, the five most common questions moms-to-be have when it comes to fetal development.

1. When will I be able to hear my baby's heartbeat?

At around 10 weeks, a Doppler ultrasound will allow you to hear your baby's heartbeat for the first time–but her heartbeat will already be visible on ultrasound by the time you are about six weeks pregnant. (To see what your baby's heartbeat looks like at six weeks, check out Drs. Doubilet and Benson's site: yourdevelopingbaby.com.)

"The first detection of the baby's heartbeat has both medical and emotional significance," says Dr. Doubilet. "From a medical standpoint, demonstration of the heartbeat is the first definitive proof that the pregnancy contains a live baby. For the parents, the first time they see or hear the heartbeat is a joyous and exciting moment as they first witness the pulse of a new life inside the mother."

When you hear your baby's heartbeat for the first time, don't be alarmed if it sounds fast. At six weeks, your baby's heart beats at about 100 to 120 beats per minute, speeding up to about 160 to 180 beats per minute at 10 weeks, then slowing to 130 to160 beats per minute by the beginning of the second trimester, where it will remain for the rest of your pregnancy.