Fetal Development Timeline: What are the exact stages?

We will analyze the Fetal Development Timeline highlighting the most important days and weeks in the development of your unborn baby. For example, when will you hear the heartbeat? When can you speak of fetal lung maturity? Most of the changes that we will focus on are on the fetus but we will also highlight some changes that occur to the pregnant mother as well.

The Fetal Development Timeline

Day 1

On the first day of pregnancy, fertilization will occur given that all conditions for fertilization are met.

Day 6

The human embryo begins to attach itself to the uterus.

Day 22

In this stage of the fetal development timeline, the fetus develops a heart that begins to beat and pump blood which is most times a different blood group from that of the mother.

Week 3

The child will have developed a backbone spinal column by the end of this week as well as a nervous system. Other organs such as the kidneys, liver and intestines are also beginning to form.

fetal development timeline

Week 4

During the fourth week in the fetal development timeline, the baby is 10,000 times larger than when the egg as just fertilized and it has started to develop skin and hair and is made up of a couple of layers. The inner layers will make up the breathing and digestive organs; the middle layer gets to make up the skeleton, circulatory system, muscles and sex organs and home pregnancy tests start testing positive for pregnancy.

Week 5 and Week 6

The child at this stage looks similar to a tadpole. Its legs, eyes and hands have begun to develop and in this stage of the fetal development timeline, an ultrasound can detect the baby's heartbeat. It is also in this stage that the baby is most vulnerable to disease, drugs and any other factors that can interfere with normal growth.

the fetal development timeline

Week 7 and Week 8

The embryo is now about 1.6 centimeters long and an ultrasound can measure the exact length of your baby. The baby's brain and its spinal cord is now growing in the neural tube along the back of the embryo. Some little notches start to appear where the fingers and toes will appear. The eyelids and nose are now distinct. By the eighth week, each bodily organ is already forming and bones are now replacing the cartilage and fingerprints form. The baby starts to hear at this stage.

Week 9 and Week 10

The baby now begins to develop fingernails. At this stage, it is possible for the baby to turn its head as well as have the hiccups. When you want to hear the fetal heartbeat and the hiccups, you can use a Sonoline B Fetal Doppler

Week 11 and Week 12

It is now possible for the baby to “breathe” the amniotic fluid as well as urinate. It can clutch its little fists and organs are functional. The baby also has a visible skeletal structure and since the most critical developments have already taken place, the chances of having a miscarriage have greatly reduced.

Week 14 and Week 15

The baby develops fully functional taste buds and the baby's heart now pumps blood on a daily basis throughout the baby's body

Week 16

The bone marrow begins to form and about 50 pints are pumped throughout the baby in one day.

Week 17

It is possible for the baby to now experience REM sleep. That is to say that the baby can now dream.

Week 18 and Week 19

The baby is now about 5 ounces (140 grams) and its nervous system is now starting to show. The genitalia are all fully developed and it is possible to determine whether it's a boy or a girl. It is possible for the baby to suck a thumb, stretch, and yawn as well as make faces. It is also at this stage that you can feel your baby move, what is normally called a quickening.

Week 20

The baby can now recognize its mother's voice and it can respond to sounds by moving or increasing its pulse.

Months 5 and Month 6

The fetus starts to practice how to breathe by inhaling amniotic fluid (fetal lung maturity)and it can grab its umbilical cord. The mother can feel the increase in the baby's movement and hiccups and its sweat gland and oil glands are also functional. It weighs around one and a half pounds and is approximately twelve inches long.

Months 7 to Month 9

The baby can open and close its eyes at will and is using up to four senses. These are vision, touch, taste and hearing. In this stage of the fetal development timeline, the baby can tell the difference between sleeping and being awake and it relates the mother's moods. Its skin thickens in preparation for life outside the womb and a fat layer is produced and stored under the skin. Protective antibodies begin to build up and the baby's heart now pumps about 300 gallons of blood in a single day. The baby will stop growing a week before being born and it turns inside the womb with its head in preparation for birth.