Throughout this week, the mature egg will detach from the uterine lining to move toward the fallopian tube and uterus. That’s where the egg and the sperm will be welded to each other and merge. The sperm’s nucleus enters the egg’s and form what is called the zygote (the first form of life of the fetus to its simplest expression). Once the zygote formation is confirmed, cell proliferation has already started.

The appearance of layers of cells ready to create the placenta for future implantation comes two weeks after fertilization. The cells are already reproducing themselves at an impressive rate and preparing your baby’s organs.

Around the third week, the embryo measures between 1 and 2 mm and weighs less than a gram. Continuing their multiplication and organization, the embryonic cells then form the third layer of cells called specific cells. They will form the baby’s future organs. The first layer is responsible for skin, teeth, hair, nails, nose, lips and the entire nervous system.

The second layer is responsible for muscles, bones, heart, blood and sexual organs, and the third layer is responsible for other organs such as the tongue, bladder, lungs, digestive system and liver. It is however only during the 4th week of your pregnancy that everything will accelerate considerably.

Also, each organ’s buds start to take form and develop. The nervous system also starts to take form and will eventually lead to the development of the brain, spinal cord and all the nerves that it comprises. The zygote has now become an embryo and has a more and more defined shape. It is now possible to differentiate the embryo from the placenta.

By the end of your first month, the embryo will measure 2 mm and will be visible with an ultrasound. His little heart makes its very very steps : it’s beating !

At the end of this month...

Baby measures about 2 mm
Baby weighs about 0 g