What's Happening Inside You:
Two weeks have passed since the first day of your last period. It’s usually toward the beginning of this week that ovulation occurs and the child is conceived. Conception itself takes about 24 hours.
Once they get there, several sperm will attempts to penetrate the protective zona pellucid, which covers the egg. But only one lucky sperm will, for a brief moment, creates a hole that’s just large enough to push through. Penetration of the egg takes about 20 minutes.
When the sperm cell is inside, the capsule closes, and just like that, it’s already been determined if your baby will be a boy or a girl (the sperm cell determines gender). The egg always holds an X-chromosome, while a sperm cell can hold either an X- or a Y-chromosome. If the combination is XX, you’ll have a girl; if it’s XY, you’ll have a boy.
This minuscule baby-to-be is called different things as it develops. This week alone the fertilized egg is called a zygote, then a morula, then a blastocyst. But from conception to Week 10, it’s usually referred to as an embryo, and from Week 10 till birth, it’s called a fetus.