A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Click a letter to see a list of conditions beginning with that letter.
Click 'Topic Index' to return to the index for the current topic.
Click 'Library Index' to return to the listing of all topics.
Pregnancy: Your First Trimester Changes
The first trimester is a time of rapid development for your baby. Because your baby is growing so quickly, it is important that you start a healthy lifestyle right away. By the end of the first trimester, your baby has formed all of its major body organs and weighs just over an ounce.
Month 1 (weeks 1 to 4)
The placenta (the organ that nourishes your baby) begins to form. The brain, spinal cord, heart, gastrointestinal tract, and lungs begin to develop. Your baby is about ¼ inch long by the end of the first month.
 |
| Actual size of baby is 1/4". |
Month 2 (weeks 5 to 8)
All of your baby’s major body organs form. The face, fingers, toes, ears, and eyes appear. By the end of the month, your baby is about 1 inch long.
 |
| Actual size of baby is 1". |
Month 3 (weeks 9 to 12)
Your baby can open and close its fists and mouth. The sexual organs begin to form. As the first trimester ends, your baby is about 3 inches long.
 |
| Actual size of baby is 3". |
Online Medical Reviewer:
Donna Freeborn PhD CNM FNP
Online Medical Reviewer:
Heather M Trevino BSN RNC
Online Medical Reviewer:
Irina Burd MD PhD
Date Last Reviewed:
12/1/2022
© 2000-2024 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.