The First Four Weeks – what the Baby is doing

The first few weeks of life, at the one month stage, the baby is very, very tiny. It is the size of a poppy seed – but what a fuss this little baby is making inside! Because of him or her, the mother’s body is undergoing revolutionary stages. And the baby itself is progressing very quickly on a day to day basis.

Since the moment of conception when the sperm fertilizes the egg, cell division rapidly doubles and quadruples continuously. The embryo is embedded in the wall of the amniotic sac, which is filled with amniotic fluid. Somewhat salty and brine, the embryo is smaller than a pinhead. Just opposite the sac is a yolk sac, think providing the baby with its red blood cells and serving as a preliminary feeding center until the placenta is ready to take over. Here is a breakdown of the components:

The embryo is in the amniotic sac
The sac is smaller – and situated next to the Yolk sac, a primary resource for the baby’s development. It provides a preliminary feeding center, and produces the baby’s red blood cells.
Encircling these paired sacs is the blastocyst, which includes the entire conglomeration. The Blastocyst is like a small ball which will become the baby. It consists of several hundred rapidly multiplying cells.
As another ‘tree ring’ around the Blastocyst are Placental cells. They resemble a pearl necklace around the Blastocyst. In a short time, these cells will form into the placenta, which is the primary feeding center for the duration of the pregnancy. These cells are responsible for the production of HCg, a hormone that only pregnant women have. This is the hormone that will produce a positive result on the mother’s home pregnancy test.
The uterine lining is blood-rich and provides a reinforced cushion for the blastocyst (baby to be) As the Blastocyst expands; it will burrow, or nest itself onto the walls of the uterus.

Now the baby’s development is becoming more and more interesting. Beginning now, at the fourth week of its development, the baby’s organ development will begin in earnest. Some will even begin to function at this time. The material for the organs is taken from two sources of embryonic cells, the epiblast and hypoblast. They are shaped in two pancake-like layers, and will over the course of the next few weeks become the embryo. Starting next week, the amniotic sac will envelop the embryo.

The placenta chain has begun to change, too. Instead of being a perfect row of cells encircling the blastocyst, it has begun to bunch up a bit and fall back, or settle into the uterine walls in order to allow blood, oxygen and other nutrients to be admitted into the blastocyst. Admission of these nutrients will help to nourish the baby and is called the preliminary placenta. The yolk sac is still working at this time as the primary feeding source but its job will soon be phased out as the placenta begins to take over its important job of feeding the ever-growing and developing baby to be.