January 11– Amanda has her period
Week 1, January 18 - We are unsure why they start the pregnancy count two weeks prior to fertilization. Should most women consider themselves pregnant for half of each month?
Week 2, January 25 – Less interesting than week 1.
Week 3, February 1 – We have sex; fertilization occurs. The fertilized ovum implants in the uterus lining and continues to multiply.
Week 4, February 8 – It is now a blastocyst and divides into an inner and outer half. The outer half will develop into the placenta, and the inner half will eventually become a baby.
Week 5, February 15- A head and tail are now identifiable. The central nervous system, brain, and spinal cord begin to form.
Week 6, February 22 – The tadpole stage – it looks like a tadpole. Amanda and I referred to the embryo as the tadpole for a few weeks. The heart begins to beat on it own and organs continue to develop.
Week 7, March 1 – Our book states, “Your baby is beginning to look more human now” and has a photograph to illustrate this. Whoever wrote that needs to meet more humans.
The embryo’s face begins to take shape. Loosely. More like black dots and holes than an actual face.
Week 8, March 8 – The baby is now around ½”. The embryo now has a tongue, nostril, and nose tip. The eyes and ears continue to develop. Bone cells replace cartilage. Joints start to form as the limbs lengthen. Most organs are present and the intestines begin to develop in the umbilical cord.
Week 9, March 15 – The 1” embryo is developing toes, fingers, and eyelids. The diaphragm develops, and the intestines begin to move from the umbilical cord into the abdomen which seems really weird.
Week 10, March 22 – The embryo has become a fetus and genitals begin to form. Big week.
Week 11, March 29 – The fetus is between 1 ¾- 2 ¼ inches. Its body nearly doubles in length this week trying to catch up in size to its previously oversized head. The irises start to develop. Most of the vital organs are fully formed and beginning to operate.
Week 12, April 5 – Organs continue to develop. Fingers and toes have separated as bones begin to harden. The fetus can now smile, frown, and suck its thumb. The fetus is still unable to fall in with the wrong crowd (unless it has an evil twin?).
Week 13, April 12 – Now 2 2/3 – 3 inches the fetus may be able to sense sounds through vibration receptors in the skin.
And that ends the first trimester.
*these summaries are based upon information from "The Pregnancy Bible"