Pregnancy Week by Week

Pregnancy Week by Week - Pregnancy Tips - Box for Two

The stages leading to birth after conception are marked with different changes to the mother and the unborn child.

Below is a summary of what happens from one week to another to the baby.

Week 1

Health care practitioners date week 1 of pregnancy at about 2 weeks before fertilization. They use the first day of the last menstrual cycle to calculate the due date. Therefore, technically speaking, you are not expecting.

Week 2

This is the ovulation week. The ovary releases a mature egg also known as an ovum into the fallopian tube. Fertilization takes place in the fallopian tube when the egg fuses with a single sperm. Therefore, in actual sense, conception occurs in week 2. At conception, all the genetic traits the baby will inherit are set up. The developing baby is known as a zygote at this stage.

Week 3

Development during week 2 leads to formation of an embryo. An embryo is a mass of cells. The embryo moves through the fallopian tube to the uterus. It burrows into the uterine wall. This process is called implantation.

Week 4

The embryo divides into two regions. One part becomes the placenta while the other half keeps on growing. The neural tube that is the foundation of the brain, the spinal cord as well as the backbone begins to form at this stage.

Week 5

The baby’s heart will begin to beat this week. The embryo develops into 3 distinct regions namely, the ectoderm (outermost layer), the mesoderm (middle layer) and the endoderm (innermost layer). Various structural components will emanate from these regions as the baby continues to grow and develop.

Week 6

The baby’s brain hemispheres are forming and its heart now beats regularly. Its heart beat is about 150 times per minute.

Week 7

The baby’s facial features are becoming distinct. The baby’s brain also continues to be more complex. The baby can also move, but it is too early to feel the movements.


Week 8

The baby continues to grow in size. The ears, the upper lip, the nose and the eyelids are taking shape. The baby’s heart is also growing stronger.

Week 9

The baby’s reproductive organs, the pancreas and the gallbladder begin to form this week. The baby’s head is approximately half the length of its whole body. Its fingers are also growing.

Week 10

By the end of week 10, the baby transforms from an embryo to a fetus. A lot of changes occur as this week comes to an end. The hands and feet take shape, its bones start hardening and the baby’s brain continues to develop.

Week 11

The baby will begin to carry out gaseous exchange this week. This means that the lungs are growing and developing.

Week 12

The baby’s movement organs continue growing and developing. While the baby’s movement becomes more pronounced, it is still too early to feel the changes.

Week 13

The baby’s facial organs are becoming more distinct. By now the other parts of the body begin to outpace the head while all the baby’s critical organs and systems are already formed.

Week 14

The sexual organs continue to develop. If the baby is a boy, its prostate begins to form and if it is a girl, the ovaries begin to move into her pelvis.

Week 15

The baby’s first hair by now covers its back, the ears, the forehead and the shoulders to insulate against heat loss. This hair falls off with time. The baby’s facial muscles become more active.

Week 16

The umbilical cord is fully mature now and the skeleton continues to develop. If the baby is a girl, many eggs begin to form in the ovaries.

Week 17

The baby’s head is now proportional to the rest of the body. Body fat and sweat glands form this week.



Week 18

The baby’s hearing system is developing and functional now. This is the best time to begin talking with your unborn baby.

Week 19

A greasy, cheese-like white coating known as the vernix caseosa starts forming under the baby’s skin. It regulates body temperature besides protecting the baby’s skin. This coating is also shed off by the time the baby is born.

Week 20

The baby’s movement becomes more pronounced. You can feel the movements since it can curl, flex and kick. Its eyebrows are also more distinct now.

Week 21

The baby is about the size of a banana. The baby sleeps for 12 to 14 hours a day. Its taste buds also begin to form. Besides, rapid brain development is underway.

Week 22

Until this week, the baby’s skin has not been opaque. It will begin turning opaque this week. The baby’s sense of touch is getting more refined thanks to the maturing nerve endings and brain cells.

Week 23

Major changes begin occurring in the brain as well as the lungs during this week.

Week 24

The baby’s inner ear is developed and therefore body posture and balance makes sense. The baby’s motion is also more profound since there is room to maneuver.

Week 25

The baby’s first fecal movement, known as meconium is forming.

Week 26

The baby’s sleeping and waking pattern is becoming more distinct.

Week 27

You are at the tail end of the second trimester. The baby is practicing breathing in and breathing out thanks to the rapidly developing lungs. You may feel the baby’s hiccups.

Week 28

This week’s major milestone is opening and closing of the eyes.

Week 29

The baby’s kicks, curls, pushes and rolls are likely to be more frequent and forceful from this week. The baby’s celebrum- the part of the brain that is associated with personality and intelligence becomes more complex.

Week 30

All the baby’s main body organs and systems are in place. From now onwards, the baby will begin increasing in size and this slows the baby’s down movement.

Week 31

The baby cannot stretch out and is at the fetal position. This will be the case until birth. The reproductive organs continue to develop.

Week 32

By this week, all the main organs except the lungs are functional. Most preterm babies born at this week, survive.

Week 33

Since there is little room to maneuver, the baby is not as active as before.

Week 34

The vernix caseosa starts to thicken and peel off. It will however persist in some body parts such as under the arms, the groin area and behind the ears.

Week 35

The baby’s head faces down towards the cervix and vagina. This is the case for most babies. In rare cases, the feet or butt are positioned to towards the cervix and vagina. This is known as the breech position and increases chances of the need for caesarian delivery.

Week 36

The baby’s sucking muscles are fully developed and it continues to accumulate more and more fat.

Week 37

The baby begins to get antibodies from the umbilical cord in readiness for birth.

Week 38

Babies come to term any time between 38 to 42 weeks. The baby is fully developed now and ready for birth.

Week 39

The baby has probably reached its birth weight and length. The baby has also accumulated enough fat deposits to survive outside the womb.

Week 40

This is the median birth week. Babies are considered fully developed for birth from week 38.