Pregnancy Update: 4 Weeks.
(okay, so it's an actual photo....just not an actual photo of MY embryo....)
Your baby at 4 weeks:
Your microscopic embryo is already hard at work this week creating the placenta, umbilical cord and the basics of his or her body.
The embryo is now made of three layers that will transform into the different parts of your baby's body. The endoderm, or inner layer, will become your baby's intestines, liver and lungs. The middle layer, or mesoderm, will become your baby's heart, sex organs, muscles, bones, and kidneys, and the ectoderm, or outermost layer, will develop into your baby's hair, skin, eyes, and nervous system. Believe it or not, your baby is already starting to look like a tiny little being (not necessarily a human being) complete with a head, a mouth opening and a primitive brain and heart.
By the end of this week, your baby measures about 1/25 inch long, about the size of a period (like the one at the end of this sentence).
Mom's body at 4 weeks:
Once Mini Me or He implants in your uterus and that placenta starts to grow, your heart starts beating more quickly. You might be putting in an extra 15 beats per minute. Until your blood volume catches up to all that extra pumping (which it won't do for a number of weeks), you're likely to feel tired most of the time. Sounds like a good reason to schedule a siesta!
(took all of this printed info from: