Pregnancy Week by Week

Pregnancy Week 3 – Your Baby

By the beginning of this week, you may very well have a new baby on the way! Ovulation generally takes place approximately two weeks before your next expected period, when your pituitary gland releases a surge of luteinizing hormone (LH). This surge of LH triggers the release of a mature egg from one of your ovaries. This egg then travels into your fallopian tube with the assistance of muscular contractions and millions of hair-like cilia. Conception most often happens about 12-48 hours after ovulation has occurred.

Fertilization usually occurs in the middle section of the tube, not in the uterus, when one sperm penetrates the outer layer and then passes through another layer, attaching to the surface and losing its tail. The membranes of the sperm and egg unite, causing the egg to react by releasing an enzyme so no other sperm can enter. The genetic material from you and your partner are combined, each supplying 23 chromosomes. Once this happens, you are most definitely pregnant!

At the moment of conception, your baby’s gender is determined already. Out of the 46 chromosomes that make up your baby’s genetic material, two of them (one from your partner’s sperm and the other from your egg) determine your baby’s sex. If the sperm that penetrated your egg has a X chromosome, your baby will be a girl and if the sperm has a Y chromosome, your baby will be a boy.

After fertilization, the egg divides and multiplies into several cells. It continues this constant division as it travels from your fallopian tube towards your uterus, until it forms a solid ball of cells. When it arrives in your uterus, after a 1- 1 1/2 week journey, it already consists of over 250 cells. Next, it attaches to the lining of your uterus (the endometrium) and implants itself, while it continues it’s rapid growth. The fertilized egg is now considered a “blastocyst”. It is made up of two layers that eventually will become the placenta and the embryo.

Your Body

Your menstrual period isn’t due yet and it’s been less than a week since you have conceived. By the end of this week, the fertilized egg may be implanting into the wall of your uterus. When this happens, you may notice some spotting and possibly mild cramping as well. Not every woman experiences this, but occasionally it does occur. This spotting is often called “implantation bleeding” or “implantation spotting” and it generally happens just before you’d expect your period to begin (approximately 3-12 days following conception), but is lighter than a normal period and typically a different color. This spotting may make you think your period has just arrived early, but in fact could be the first sign conception has taken place.

A few women who are very in-tune with their bodies, especially those who are trying to conceive, may start noticing breast changes as early as now. Sensitive, sore nipples and swollen breasts are not uncommon as one of the very first symptoms of early pregnancy. This is due to all the many hormonal changes happening within your body.

Besides possibly experiencing a little spotting at the time of implantation and maybe tender breasts by the end of this week, your body probably isn’t letting you know you’re pregnant quite yet. There are no obvious physical changes, even though there’s a lot going on inside you. The majority of women have no idea they’re pregnant at this point, because their period won’t be late for another week or so. A few very sensitive pregnancy tests may be able to detect the tiny amount of human chorionic gonadotropin (hCG) that is already being produced by your body by the end of this week, but almost all would give a false negative if taken now. To get the most accurate result, it is best to wait until your period is at least one day late.

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