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Week 1
Pregnancy is said to begin on the first day of a woman's last menstrual period (LMP) and lasts until birth, spanning about 40 weeks. -
Week 2
During week 2, the ovaries prepare about 3-10 eggs for ovulation, while the uterus forms a thick blood-rich lining (endometrium) designed to cushion/support the baby throughout pregnancy. About 14 days after the first day of LMP, an egg is released down the fallopian tube to potentially join with a sperm in a process known as fertilization. -
Week 3
If the egg is fertilized, it immediately begins replicating its genetic information (DNA) and dividing to create more cells, gradually moving toward the uterus. -
Week 4
The egg, now called a blastocyst, is a mass of 50-60 cells about 1/100 of an inch long. Once the blastocyst enters the uterus, it burrows itself into the uterine wall, and begins to release human gonadotrophin hormone (hCG). -
Week 5
The cells of the ovum then begin to divide into the amniotic sac, where the fetus is held, and placenta, which becomes an important source of nourishment to the developing baby. Nerve growth occurs as well. -
Week 6
At this point in pregnancy, major body organs and systems are beginning to form. A few notable structures are the brain, which has divided into five sections, the heart, and the spinal cord. -
Week 7
The baby is starting develop its eyes, inner ears, and mouth, as well as arms and legs, all the while other organs continue undergoing refinement. Physical symptoms of pregnancy, such as fatigue, nausea, frequent urination, and sore breasts, also become apparent. -
Week 8
In the eighth week, the arms and legs continue to grow, facial features become more defined, and the baby's blood type is established. Muscle fibers have been forming as well, and muscle development is sufficient enough for the baby to practice movement. -
Week 9
Inside the amniotic sac, the baby is swimming around in fluid and is about an inch long. In addition, fingers and toes are becoming distinguishable as well as veins under its thin, translucent skin. -
Week 10
Nearly all body parts of the embryo, now called a fetus, are in place and begin to function at a basic level. Reproductive organs will soon begin to form. -
Week 11
At week 11, the baby should be able to swallow or stick out its tongue. Much of the cartilage now begins to calcify into bone and the baby more closely resembles a newborn. -
Week 12
At this point, the heartbeat can now be heard though a fetal doppler. The vocal cords have also finished forming and the baby can feel pain. Spontaneous movement is common. -
Week 13
The child's body is now able to produce insulin and has formed its own unique fingerprint. Though the child can kick its arms and flex, the mother may not be able to feel anything yet. -
Week 14
The baby is able to make breathing movements and starts to develop hair. Moreover, it develops a covering of hair (lanugo) to protect the skin while in fluid until it is shed before birth. -
Week 15
The child's body has become more proportional, with the body being larger than the head and hands. The skeletal system continues to grow and the inner bones of the ear are formed. -
Week 16
Now the baby can hear external voices, sleep/dream, and make facial expressions. It can also grasp, kick, and somersault. -
Week 17
In week 17, fat deposits develop under the skin to provide energy and warmth to the child after birth. In addition, the eyes are now looking forward, but remain closed. -
Week 18
Routine periods of activity and rest are recognizable. With regards to development, vernix, a protective wax layer, is being built around the baby's skin, and alveoli is being formed in the lungs. -
Week 19
Much of the baby's reproductive organs have been formed, along with its genitals. Therefore, an ultrasound can predict the baby's gender with considerable accuracy. -
Week 20
This week is the midpoint of pregnancy, with about 4 more months to go. This is an important time for sensory development in relation to the brain. The baby is also likely able to recognize voices. -
Week 21
Bone marrow is now producing blood cells instead of the liver/spleen. A birth date can also be approximated based on the size of the baby's head. -
Week 22
By this week, the baby, who is now about 11 inches long, might frequently react to sound. Pregnancy is also clearly visible at this point because of the uterus' size. -
Week 23
The ear, being fully developed, enables the child to gain a sense of balance when they move. Skin pigment forms as well during this time. -
Week 24
The baby's lungs are developing the branches of the bronchial tree. At the same time, since taste buds are fully developed, the baby may display a preference or aversion to certain foods. -
Week 25
The brain continues to grow rapidly and cerebral/neural cells mature. One may also notice the baby's improved dexterity. -
Week 26
Though the baby has been breathing for a few weeks now, there is still no air in the lungs. The mother may experience Braxton Hicks contractions, which cause the uterus to contract and relax between intervals. -
Week 27
The child looks similar to how they would at birth. Interaction with the baby whether via music, conversation, reading, etc. is recommended. -
Week 28
At week 28, brain waves show rapid eye movement (REM) sleep and the eyes are able to open as well. If born now, the child would have a 90% chance of survival. -
Week 29
The head continues to grow in order to accommodate the brain, which is developing billions of neurons. The baby may continue to kick and stretch, although movements may become less frequent as there is less space in the womb. -
Week 30
By week 30, the baby's wrinkled skin gradually starts to become smoother, and the body stores iron, calcium, and phosphorus. Its body also controls its temperature. -
Week 31
Now that the lungs, digestive tract, and major organs in general are functioning effectively, the primary focus is building fat and muscle. -
Week 32
At this part of pregnancy, the baby can be found sleeping most of the time. It weighs probably somewhere around 4 pounds. -
Week 33
Lanugo will begin to disappear to be replaced with real hair. Also, the baby's nails typically reach the tips of their fingers. -
Week 34
At this point, the child has a substantial chance of survival outside the womb. It may even be turned upside down into the birthing position as contractions increase in number. -
Week 35
By this time, reflexes are coordinated, enabling the baby to respond to numerous stimuli. Though the baby possesses much more stores of fat, it's still not enough to sustain their body temperature outside the womb. -
Week 36
The only organs left to completely develop are the lungs. "Lightening" or "dropping" may occur, in which the baby drops into the birth canal. -
Week 37
In these last weeks, pregnancy is considered "at term", basically meaning that the mother's water can break and labor can occur at any time. Discharge/cervical mucous may be noticeable. -
Week 38
The average baby is about 40 inches and weights about 7.5 pounds. At this time, it will have shed the lanugo coating and ingested it to store in its bowels. -
Week 39
The baby is finally ready for life outside its mother's womb. To prepare for birth, the mother may experience intense contractions, which can be painful. -
Week 40
At birth, the umbilical cord will stop working the moment the child takes its first breath, ending pregnancy. Babies can be born blue or grey eyes, and it may take months for its true color to take shape.
