Week 12 of Pregnancy: What's Going On Inside

Overview

By week 12, you can now hear a fetus's heartbeat with a Doppler heart monitor.

Wondering what a fetus looks like at 12 weeks? It is now about the size of a lime.

How a fetus is changing

Here are some important changes that happen around this time.

• By 10 weeks of pregnancy, an embryo has nearly all of the body structures that adults have. Its brain is now more complex. After this point, we call it a fetus.
• During this month, the fetus's limbs, hands, and head start to move. Eyelids cover their eyes, and their fingernails are starting to grow.
• At the end of this month, fetuses start a big weight gain.