Day of Conception
The egg and the sperm unite to form a single cell called a zygote, which is smaller than a grain of sand. The zygote contains all the genetic information, including such things as the color of hair, the fine lines of the fingerprint, the gender, physical appearance and skin tone.
The cells continue to divide and an embryo is now formed. Around days 3 to 4 in a typical pregnancy, the embryo reaches the uterus after traveling through the fallopian tube.
A pregnancy test taken at this point can measure hCG in the mother’s urine. The embryo is now completely attached to the uterus and is receiving nourishment from the mother.
The heart is about the size of a poppy seed and is the first organ to function.
The brain and spinal cord has formed. The eyes are developing and the arm and legs buds can be seen. The beating heart is visible on an ultrasound and actually beats 80 times per minute.
The embryo is now 1/3 inch long and making its own blood. Depending on gender, the testicles or ovaries are beginning to form.
The elbows and fingers can be seen. Lungs begin to develop. Taste buds are forming on the tongue and tooth buds for baby teeth are taking form. Eyelids are also beginning to form.
The ears and nose are visible and there is pigment in the retina. Nipples can be seen on the chest and limbs and fingers are growing rapidly. The bones in the arm are beginning to calcify and harden.
The brain is growing rapidly and produces almost 250,000 new neurons every minute. The brain can now make muscles move on purpose. The external ear is clearly seen and a baby boy begins to produce testosterone.
The baby has all the major organ systems and is now called a fetus because it is distinctly recognizable as a human being. Fetus is the latin word for “young one”. The fetus can now yawn and suck. The kidneys now produce urine. During the next several weeks, the body will grow rapidly, increasing in weight 30 times and tripling in length.
The fetus now sleeps and awakens. Through turning its head, curling its toes and opening and closing its mouth, it exercises its muscles. Amniotic fluid is now being breathed to help develop the respiratory system. If the palm of the fetus is stroked, it will make a tight fist.
14 Weeks (3.5 Months)
The fetus is coordinated enough to find his thumb and suck it. Finger and toe nails are beginning to form. The fetus can swallow and urinate.
16 Weeks (4 Months)
The heart pumps 6 gallons of blood per day. If the baby is a girl, millions of eggs are forming in her ovaries. The baby can now coordinate moving arms and legs.
Reflexes such as blinking and frowning are now developed. The mother can now feel fetal movement, called “quickening”.
20 Weeks (5 Months)
The fetus is now 10 inches long and has waking and sleeping patterns, as well as a favorite sleeping position.
The fetus now weighs 1.5 pounds and can recognize his mother’s voice. Some babies born at this stage are able to survive.
The baby can now react to sounds outside the mother’s body. Teeth buds are apparent, eye lashes and eyebrows are well formed and hair on the baby’s head is growing longer.
The brain is now developed enough to coordinate rhythmic breathing. The skin becomes less wrinkled and smoother, as the baby continues to gain weight.
The baby now weighs about 4.5 pounds and is about 17 inches long. The eyes are wide open, the head is covered in hair and the fingernails have reached the tips of the finger.
The baby now has a plump body and firm grasp. Typically the head is down in the mother’s pelvis, awaiting birth.