Skip to content
My WebMD Sign In, Sign Up

Health & Pregnancy

Font Size

Baby Development 1st Trimester Highlights

A lot has happened in the past three months. Your baby is only 3 or 4 inches long, but already can open and close his fists and mouth. Fingernails and toenails are just beginning to develop. Already, your tiny baby has:  

  • A brain, spinal cord, and flexible backbone.
  • Lungs that are not fully developed.
  • A heart that beats 120 to 160 beats per minute.
  • All major organs, but not fully developed.
  • A soft skeleton.
  • Eyes with eyelids that stay closed.
  • A nose, mouth, and chin.
  • Distinct fingers and toes and tiny fingernails.
  • Genitalia, not fully developed.
  • Little teeth buds.

WebMD Medical Reference

Reviewed by Traci C. Johnson, MD, FACOG on July 05, 2014

Pregnancy Week-By-Week Newsletter

Delivered right to your inbox, get pictures and facts on
what to expect each week of your pregnancy.

Today on WebMD

Woman smiling as she reads pregnancy test
Slideshow
pregnant woman with salad
Quiz
 
pregnancy am i pregnant
Article
calendar and baby buggy
Tool
 

slideshow fetal development
Slideshow
pregnancy first trimester warning signs
Article
 
What Causes Bipolar
Video
Woman trying on dress in store
Slideshow
 

pregnant woman
Article
Close up on eyes of baby breastfeeding
Video
 
healthtool pregnancy calendar
Tool
eddleman prepare your body pregnancy
Video