If you’re pregnant, it’s important for you to know about fetal development. On this page, dating is from conception which is typically about two weeks after the mother’s last menstrual period. From conception to birth, here are some important milestones:

For more information as well as illustrations, please visit the National Library of Medicine at the following link:


Day 1

When a sperm meets an egg, a zygote is created with its own unique DNA. Cells begin replicating and splitting immediately.


Day 5

For several days, the zygote’s cells replicate and multiply while it travels down the fallopian tube to the uterus. By this point, it is called a blastocyst.


Day 6-7

The blastocyst attaches to the lining of the uterus in a process called implantation. Now it is called an embryo.


Day 20

Foundations of the brain, spinal cord, and nervous system are already established.


Day 21

The heart begins to beat.


Day 28

The backbone and muscles are forming. Arms, legs, eyes and ears have begun to show.


Day 35

Five fingers can be discerned in the hand. The retina of the eye is forming.


Day 40

Brain waves can be detected and recorded.


Week 6 (from conception)

The liver is now taking over the production of the blood cells, and the brain begins to control movement of muscles and organs. All the internal organs the baby will have as an adult are in various stages of development. The mother is about to miss her second period and has probably confirmed that she is pregnant.


Week 8

A little more than an inch long, now it is called a fetus. All organ systems are in place.


Week 9

Fingerprints are already evident in the skin.


Week 10

The fetus can squint, swallow, and wrinkle its forehead.


Week 12

The fetus now sleeps, awakens, and exercises its muscles energetically – turning its head, curling its toes, and opening and closing its mouth. Bones are rapidly forming.


Week 13

Fine hair has begun to grow on the head, and sexual differentiation has become apparent.


Month 5

Half the pregnancy has now passed, and the fetus is about 12 inches long. The mother can definitely feel movement by now. If a sound is especially loud or startling, the fetus may jump in reaction to it. Its fingernails are growing rapidly.


Month 6

If the baby were born in this month and given the proper care, it could survive. Finger and toe prints can be seen. The eyelids begin to part and the eyes open.


Month 7

The baby has developed four of its senses: vision, hearing, taste, and touch. It can recognize its mother’s voice. The baby can suck its thumb.


Month 8

The skin begins to thicken with a layer of fat stored underneath for insulation and nourishment. Antibodies increasingly build up.


Month 9

Toward the end of this month the baby is ready for birth. The average duration of pregnancy is 40 weeks from the first day of the mother’s last menstrual period, but this varies. Most babies (85-95{909da48ad593815cb90f20faf8b9ea30c7655185ddd4210efebf3c3df1113258}) are born somewhere between 38 and 42 weeks. By this time, the infant normally weighs 6 to 9 pounds, and its heart is pumping about 250 gallons of blood a day. It is fully capable of life outside the womb.