Pregnancy Week 3
Age of fetus 1 week.

How Big Is Your Baby?
The embryo growing inside you is very small. At this point, it is only a group of cells that are multiplying and growing rapidly. The embryo is the size of the head of a pin and would be visible to the naked eye if it weren't inside you. The group of cells doesn't look like a fetus or baby; it looks like the illustration on page 48. During this first week, the embryo is about 0.006 inch (0.150mm) long.

How Big Are You?
In this third week of pregnancy, you won't notice any changes. It's too soon! Few women know they have conceived. Remember, you haven't even missed a period yet.
How Your Baby Is Growing and Developing

A great deal is happening, even though your pregnancy is in its earliest stage. Ovaries lie free in your pelvis (or peritoneal cavity). They are close to the uterus and Fallopian tube. At the time of ovulation, the end of the tube (called the fimbria) lies close to the ovary. Some researchers believe this tube opening covers the area on the ovary where the egg (ovum) is released at the time of ovulation. The release site on the ovary is called the stigma.

During intercourse, an average of 0.06 to 0.15 ounce (2 to 5ml) of semen is deposited in the vagina. Each milliliter contains an average of 70 million sperm; each ejaculation contains 140 to 350 million sperm. Only about 200 sperm actually reach the egg in the tube. Fertilization is the joining together of one sperm and an egg.