Your Pregnancy: 5 Weeks

How your baby's growing: Deep in your uterus your embryo is growing at a furious pace. At this point he's about the size of a sesame seed, and he looks more like a tiny tadpole than a human.

He's now made up of three layers — the ectoderm, mesoderm, and endoderm — that will later form his organs and tissues.

The cells are forming for his major organs, including his kidneys and liver, and his neural tube is beginning to develop.

This neural tube — from which your baby's brain, spinal cord, nerves, and backbone will sprout — develops in the top layer, called the ectoderm. This layer will also give rise to his skin, hair, nails, mammary and sweat glands, and tooth enamel.

His heart and circulatory system begin to form in the middle layer, or mesoderm. (This week, in fact, his tiny heart begins to divide into chambers and beat and pump blood.)

The mesoderm will also form your baby's muscles, cartilage, bone, and subcutaneous (under skin) tissue. The third layer, or endoderm, will house his lungs, intestines, and rudimentary urinary system, as well as his thyroid, liver, and pancreas.

In the meantime, the primitive placenta and umbilical cord, which deliver nourishment and oxygen to your baby, are already on the job.*

Note: Experts say every baby develops differently — even in the womb. This developmental information is designed to give you a general idea of how your baby is growing.

How your life's changing:

Pregnancy symptoms may surface this week if they haven't already. I

f you're like most women, you'll notice nausea (and not just in the morning), sore breasts, fatigue, and frequent urination.

All are normal, all are annoying, but the upside is that they're all a part of being pregnant and won't last forever.

The outside world won't see any sign of the dramatic developments taking place inside you.

You'll also want to continue or start an exercise routine. Exercise helps you develop good muscle tone, strength, and endurance; plus, it helps you manage the extra weight you'll be carrying and get ready for the physical rigors of labor.

You'll also find that bouncing back after you give birth will be easier if you've already established a workout routine. Choose a safe, moderately vigorous activity you like (walking and swimming are fine choices for pregnant women).

For Dads, there are plenty of ways to participate in your partner's pregnancy — even this early in the game.

Source: Babycenter.com