Picture of First Trimester (4 Weeks)

First Trimester: The Baby at 4 Weeks

Your baby's brain and spinal cord have begun to form.
The heart begins to form.
Arm and leg buds appear.
Your baby is now an embryo and 1/25 of an inch long.

Related Topics
Stages of Pregnancy Slideshow

Reviewed by William C. Shiel Jr., MD, FACP, FACR on August 21, 2009

Image Source: Copyright © Medical RF / Phototake -- All rights reserved.

Text: Womenshealth.gov - Healthy Pregnancy: Stages of Pregnancy