Week 5. Your little embryo, which at this point resembles a tadpole more than a baby (complete with teeny tail), is growing fast and furious and is now about the size of an orange seed – still small, but a lot bigger than it’s been.
This week, the heart is starting to take shape. In fact, the circulatory system, along with the heart, is the first system to be operational. Your baby’s heart is made up of two tiny channels called heart tubes – and though it’s still far from fully functional, it’s already beating – something you might be able to see on an early ultrasound.
Also in the works is the neutral tube, which will eventually become your baby’s brain and spinal cord. Right now the neural tube is open, but it will close by next week.
Week 6. Crown (head) to rump (bottom) measurements are used for babies in utero because their tiny, newly forming legs are bent, making it difficult to measure the full length of the body.
Hows baby measuring up this week? That crown to rump measurement has reached somewhere between a fifth and a quarter of an inch. This week also the beginning of the development of your baby’s jaws, cheeks, and chin.
Little indentations on both sides of the head will form into ear canals. Small black dots on the face will form the eyes, and a small bump on the front if the head will turn into a button nose in a few weeks’ time.
Also taking shape this week : your baby’s tiny heart is beating 80 times per minute and getting faster each day – a stat that’s probably got your heart racing.
Week 7. Here’s an amazing fact about your baby right now: He or she is 10,000 times bigger now than at conception – about the size of a blue berry. A lot of that growth is concentrated on the head (new brain cells are being generated at the rate of 100 cells per minute).
Your baby’s mouth and tongue are forming this week and so are his or her arm or leg buds, which are beginning to sprout into paddle-like appendages and to divide into hand, arm, and shoulder segments.
Also in place now are your baby’s kidneys, and they’re poised to begin their important work of waste management (i.e., urine production and excretion). At least you don’t have to worry about dirty diapers yet!
Week 8. Your baby is growing up a storm, this week measuring about half an inch in length, or about the size of a large raspberry. And that sweet little raspberry of yours is looking less reptilian and more human (happily), as his or her lips, nose, eyelids, legs, and back continue to take shape.
And though it’s still too early to hear from the outside, your baby’s heart is beating at the incredible rate of 150 times per minute.
Something else new this week : Your baby is making spontaneous movements (twitches of the trunk and limb buds too tiny for you to feel).