Within the first week of coneption, while still in the fallopian tube, the egg divides into many cells, forming an embryo, and keeps dividing as it travels to the uterus. When the cells have divided into 32 cells, it is called a morula. After multiple rounds of more cell division, cleavage, has produced 100 cells, the embryo is called a blastula. When the blastula reaches the uterus and implants itself into the uterine lining, it is now called a blastocyst. This is moment, pregnancy has officially taken place. Placental tissue secretes a hormone called hCG. This hormone supports the endometrial lining, which will support pregnancy.
During the second month of pregnancy, the baby's facial features continue to develop. A skeleton made of cartilage is formed. Little flaps of skin that will develop into ears, little nubs which will become the arms and legs, fingers, toes, and eyes will also form and develop during this time. Around week six, the baby's first heartbeat and brain waves are made. By the end of this month, the baby becomes about a fetus that is about an inch long.
Throughout the third, and final, month of the first trimester, the baby now has arms, hands, fingers, legs, feet, toes, and can open and close its fist and mouth. Toenails and fingernails begin to develop, as well as the external ears. Teeth begin to form along with the baby's reproductive organs, although ultrasounds are not able to determine the sex of the baby just yet. The baby's circulatory and urinary systems are able to work and the liver can produce bile. Around week seven, the umbilical cord is formed. The baby is now 3-4 inches and weighs one ounce. After the first trimester is complete, the chances of miscarriage drop considerably.
The placenta begins to develop along with a primitive face, mouth, lower jaw, and throat.
Little nubs that will grow into arms, fingers, toes, and eyes begin to develop.
The baby has arms, legs, fingers, hands, feet, and toes. It can now open and close its mouth and fist.
By the fifth month, the baby's arms and legs have developed more, and can move them around in the uterus. Myelin begins to cover the baby's nerves. The baby now has little eyelashes and eyebrows, and is covered in lanugo, which is a "fur coat" to keep the baby warm until she/he builds up more fat in their system.
In the sixth month, the baby's brain has developed enough to open and close the baby's eyelids. The bones continue to grow stronger. Also, capillaries begin to form to carry oxygenated blood throughout the body.
The baby has fingerprints and is able to yawn and hiccup. The baby's brain can control its heartbeat.
Arms and legs have developed more and can move in the uterus. The baby now has eyelashes and eyebrows.
The baby's brain can open and close the eyelids and oxygenated blood is now circulating throughout the baby's body.
By the eight month of pregnancy, the baby weighs about 5 lbs, and continues to develop more fat. The brain is swiftly developing at this point, so the baby can now see and hear. Most of the internal systems have developed, although the lungs may still be immature.
During the ninth, and final, month of pregnancy, the baby is still growing and maturing. The lungs are fully developed, his/her reflexes are now coordinated so the baby can turn their head, respond to stimuli, and they have a firm grip. The baby will position itself towards the birth canal so he/she is ready for delivery. By the end of this month, the baby is ready to come into the world!
The baby can respond to sound, light, pain, and light.
The baby can see and hear as the brain rapidly develops.
The baby can turn its head, respond to stimuli, and they have a firm grip.