Welcome to your pregnancy! This is a huge week, when you actually conceive your baby by joining egg with sperm. Since not all women are aware of exactly when this miraculous event occurs, pregnancies are said to begin from the date of the last menstrual period (that explains why we're already at week three!). Here are a few things to know about what's happening with your baby and your body this week.

1. Hooray for Conception!

This is the week of conception! You read that right: the first two weeks of your normal cycle--when your body is preparing to ovulate--are counted as the first two of the 40 pregnancy weeks. But it’s this week, when the sperm meets the egg and it becomes a single fertilized cell, when your body gets the signal that there’s a baby—currently known as a zygote—on board.

2. Division Game

The zygote immediately develops a protective membrane around itself, to ward off any other sperm from entering. Then it begins to divide--one cell becomes two, which becomes four, which becomes eight, etc--but it remains crazy tiny (smaller than the head of a pin!).

3. Making a Move

While it’s dividing, the zygote—now called a blastocyst—is also on the move, traveling from your fallopian tube to your uterus. This journey takes about six days. You’re probably not aware of your pregnancy yet; you haven’t missed your period yet and you shouldn’t be experiencing any pregnancy symptoms.