A Closer Look: Development
1st Trimester (Weeks 1 – 13)
Week 1 (Day 1)
First day of your last normal menstrual period.
Week 2 (Day 14)
The egg is released from the ovary. Fertilization takes place when a sperm joins an egg. Every detail of development, including sex, hair and eye color is determined at this point.
The embryo’s brain, spinal cord, and nervous system begin to form. The heart begins to pump blood with his or her own blood type.
All of the internal organs are present and forming. The heartbeat can be seen and heard beating on ultrasound.
Arms with hands and finger buds, and legs with feet and toe buds are visible.
Brain activity is measurable. By this time the embryo shows reflexive response to touch. The embryo begins to move.
Internal organs are functioning. The body is nearly complete. Changes after this week are primarily changes in size, rather than in appearance. The embryo is now called a fetus, or “young one” in Latin.
2nd Trimester (Weeks 14 – 26)
The fetus moves vigorously and can make a tight fist. The sex of the child can be determined.
There is evidence the baby can experience pain. The baby begins to hear. Ultrasound reveals arm and leg movements, most too slight to be felt by you.
Head and body hair are visible. The fetus jumps in response to loud noises. He or she can now swallow.
If the baby was born during this month and given special care, he or she could survive.
3rd Trimester (Weeks 27 – 40)
The fetus experiences rapid weight gain and is ready for birth.
Content taken with permission from the following informational pamphlet:
Unpregnant is not a word | © Frontlines Publishing 2011