What to Expect in the First Trimester
The first thing a woman will wonder when she finds out that she is pregnant, is what changes are happening already in her body and how her baby is developing. The first trimester is a time of major changes in her body, and the developing fetus will undergo unbelievable growth.
When the egg is fertilized, it will have created a brand new cell. All of the traits that will be unique to the baby happen at the time of fertilization. This cell will then divide and multiply as it travels down the fallopian tube. At about the first week after conception, this mass of cells will implant itself onto the wall of the uterus. The placenta and amniotic sac will be developing and the cluster of cells becomes what is known now as the embryo.
The embryonic phase goes from about the third week after conception until around the eighth week. This is a time of massive development and is a crucial time in the pregnancy. All of the baby’s major organs – the heart, brain, spinal cord – along with all the other organs in the body, will be formed during this period.
The neural tube along the baby’s back closes around the fourth week, and the heart begins to beat, pumping blood through the body. The baby’s brain and face begins to develop very quickly around the fifth week, and after the sixth week, the baby will be moving its small arms and legs. This movement likely won’t be felt however.
The trunk starts to straighten, and by the ninth week, bones continue to grow, and eyelids are forming. The eyelids will start to close to protect the baby’s eyes as they develop. The placenta is completely formed and nourishment is passing from mom to baby. The baby’s head makes up about one half of its length, and around week twelve, it will officially become a fetus. Normally, the length of the fetus around this time is from 2 to 3 inches and will weigh around 1 ounce.