@ 28 Weeks

This week, Peanut's brain begins changing. For the first two trimesters, the brain is quite smooth, but beginning this week it develops the familiar grooves, channels, and ridges characteristic of normal brains. His eyelashes and eybrows begin growing now, and the hair that has been on his head for a few weeks begins growing longer.
Monica saw the doctor yesterday, and everything looks good. They gave her a shot (apparently quite cold and therefore painful) to prevent any problems from arising closer to full term should the baby's blood type be different from Monica's. This leads me to the Holy Crap! element for the week. The placenta is now growing rapidly. It began connecting with the embryo as early as the second or third week of development, when it also made a connection to the uterun wall. As the placenta grew in its early stages, its cells grew through the walls of Monica's blood vessels to establish contact with Monica's blood stream, without Monica's blood or the baby's blood ever mixing. The placental cells also grew toward Peanut, eventually becoming the umbilical cord, enabling the baby to receive the nutrients and oxygen in her blood, and to get rid of carbon dioxide and other waste products. Where the placenta actually makes blood vessel connections with the uterun wall are called villi (see illustration of villi above), and they grow into a honeycomb-like structure that absorb the oxygen and nutrients from Monica's blood, and transfer them to the umbilical vein and into Peanut. Then, when his little circulatory system has used up the oxygen and nutrients, the waste products leave his little body through the umbilical arteries (the umbilical arteries and veins make up the umbilical cord), and Monica's blood stream absorbs them through the villi, and her body gets rid of them. Did I mention that Monica's blood and Peanut's blood never mix, even though the placenta's cells have grown through her blood vessels? Holy Crap.