Skip to content
My WebMD Sign In, Sign Up

Health & Pregnancy

Font Size

Twins Development 1st Trimester Highlights

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

  • Brains, spinal cords, and flexible backbones.
  • Lungs, but not fully developed.
  • Hearts beating 120 to 160 beats per minute.
  • All major organs, but not fully developed.
  • Soft skeletons.
  • Eyes with eyelids that stay closed.
  • Noses, mouths, and chins.
  • Distinct fingers and toes and tiny fingernails.
  • Genitalia, but not fully developed.
  • Little teeth buds.

WebMD Medical Reference

Reviewed by Matthew Brennan, MD on October 02, 2012

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
babyapp
NEW
 

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