Baby's Growth and Development at 3 Weeks: Fertilization and Implantation
Although you don't know it yet, you might have conceived already! Fertilization occurs when an egg and sperm connect and form a single cell, called a zygote. Here's what's going on during your 3rd week of pregnancy:
- By the 3rd week of pregnancy, the microscopic-sized zygote divides again and again, growing at an astounding pace in your body.
- At 3 weeks pregnant, your baby already has all of the genetic material she needs for life — half of the 23 pairs of chromosomes from you and half from your partner.
- Your baby's sex already is determined.
The Great Divide
Approximately 12 hours after fertilization, your baby — right now only a one-celled zygote — divides into two identical cells. These two cells each split, creating four cells, which then split to become eight. This continues as the total number of cells in your baby doubles every 12 hours.
If a single zygote splits into two identical zygotes, each with the same genetic makeup, identical twins occur.
During your 3rd week of pregnancy, your zygote is moving down the fallopian tube to your uterus.