Week 2

Your Baby's Development
Are you dreaming of pink or blue? Although you'll have to wait to find out what color to paint the nursery, your baby's sex is determined at the moment of fertilization, which may occur at the end of this week. Out of the 46 chromosomes that make up your baby's genetic material, two chromosomes - one from the sperm and one from the egg - determine the baby's sex. Every egg has an X chromosome; a sperm can have either an X or a Y chromosome. If the sperm has an X chromosome, you'll have a girl; if the sperm has a Y chromosome, your baby will be a boy.

Although your baby was just conceived, he or she is already working overtime. The fertilized egg goes through a process of division. Thirty hours after fertilization, it divides into two cells, then four cells, then eight, and it continues to divide as it moves from the fallopian tube to the uterus. By the time it gets to the uterus, this group of cells numbers 32 and is called a morula. One week after fertilization, there are 250 cells.

Your Body
Your uterine lining, which will nourish the baby, is developing, and your body secretes follicle-stimulating hormone (FSH), which stimulates an egg to mature. At the end of this week, the egg will be released into the fallopian tube.

You are now at the midpoint of your menstrual cycle (if you have a regular 28-day cycle), ovulation, and you're most likely to conceive. If you have sexual intercourse without protection during this week, you can become pregnant. After your partner ejaculates, millions of sperm travel from the vagina to the fallopian tube, where your egg is waiting. An enzyme is released that allows one sperm to penetrate the egg, and fertilization takes place. During fertilization, the genetic material of the sperm and the egg are combined. You are now pregnant - although your body is not yet letting you know that you are.