Presented by Dr. Alice W. Ko, MD (OB-GYN) of SexHealthGuru.

Those double lines can only mean one thing: you're pregnant! Whether you're thrilled or surprised, you'll want to know what you can expect during that first month. It may seem strange, but it's true. By the time you see that positive result, you've already been pregnant for nearly four weeks!

It's difficult for doctors to pinpoint the EXACT moment when sperm meets egg. So to keep things consistent, most consider the start date of your 40-week pregnancy to be the first day of your last period.

For the first two weeks before your egg is fertilized, your body is training itself for your pregnancy...even if you don't plan to have a baby! During this time, your uterus sheds its lining and your body releases estrogen, which promotes the growth of a new one. You also release a hormone called LH, encouraging your ovaries to release an egg 24 to 36 hours later.

Once your egg is released, you are able to get pregnant. If a sperm meets the egg during this time, you will become "officially" pregnant. The fertilized egg will spend the next two weeks making its way down your fallopian tubes into your uterus. There, it will burrow into the uterine wall to make its home for the next nine months.

By the end of the first month, your baby will be about the size of a poppy seed. But don't let that tiny size fool you. That baby has already made significant strides! He or she -yes, sex has already been genetically determined - has developed specialized cells, which will become bones, organs, muscles, hair, and skin. Your baby is also forming its placenta, which is the organ that provides food and oxygen, as well as its amniotic sac, which are thin membranes filled with fluid to cushion your baby.

Expect to feel pretty normal those first two weeks after conception, as your body continues its usual cycle. After your egg is fertilized, you may experience typical PMS symptoms, such as mood swings, bloating, and cramping, although some women don't even notice this. During week four, some women experience very light bleeding as the egg burrows into the uterine wall. This can be completely normal, and may not be an indication that something is wrong.

Because the changes during month one are so miniscule, it's unlikely you'll know you're pregnant before seeing that positive test. But if you're trying, it's never too early to ACT like you're pregnant! That means eating nutritious foods and exercising moderately. You should also start taking a prenatal vitamin, since the folic acid in it may help prevent birth defects of the brain and spinal cord. At the same time, restrict your alcohol intake and avoid smoking and other potentially harmful activities.

As soon as you know you're pregnant, it's time to make that initial appointment with an obstetrician-gynecologist. He or she will guide you through the following months and help to ensure your healthiest child! To see an expanded video on your first month of pregnancy, please visit SexHealthGuru.