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Find out How a Baby Develops Week by Week during the 42 weeks of Pregnancy

Find out How a Baby Develops Week by Week during the 42 weeks of Pregnancy.


he week-by-week baby development in the womb is a steady and gradual process that happens day and night. In this guide, you are going to learn what significant events happen each week of the baby's development in the womb. The process spans over a period of 40 weeks. The process starts before conception and lasts to the final week of the pregnancy. 

Week 1

Week one is the first week of the pregnancy and is about two weeks before the actual conceptions take place. This week starts from the last day of your menstrual period. This method of calculation is based on the fact we can establish the exact time of conception when the egg and sperm fuse to become one. 

Week 2 

Ovulation takes place in week 2. The ovary releases a ripened ovum into the fallopian tube. During this week, the conception has not happened yet. Technically the baby does not exist yet. 

Week 3 

Conception happens within the third week. After conception, all the other factors such as eye color, skin, hair color, and body size. During this period, the child is referred to as a zygote and has a total of 46 chromosomes, 23 from each parent. The zygote becomes a ball of cells called an embryo after fertilization is complete. It then travels along the fallopian tube to the womb. They may be fraternal twins if two eggs fertilized or identical if one egg split into two fetuses. 

Week 4 

During the fourth week, the embryo is already in the womb. It separates into two main sections. One section develops to become the umbilical cord while the other part develops to become a sheet of cells. These sheets of cells soon develop into the neural tube. The backbone, spinal cord, and brain will develop from that neural tube. 

Week 5 

During this week, the embryo is now growing continuously. It is made of three layers. The outer layer is called the ectoderm. It later develops into ears, eyes, nervous system, inner ear, and other connectives tissues. The middle layer called the mesoderm develops to become the heart and circulatory system. The inner layer is the one that forms organs such as lungs, intestines, and the bladder. 

Week 6 

During this week, the heartbeats can be observed in an Ultrasound the while the brain hemispheres will also be developing. The heart at this point will be making 150 beats per minute till the child is born. The brain waves can be recorded at this time. 

Week 7 

During this week, the baby's brain is growing at an incredible rate, about 100,000 cells per minute. The baby will also be making tiny movements only visible by the ultra scan. 

Week 8 

The baby's features such as eyes and mouth will start to take shape at this stage. The baby's weight has also quadrupled by this time. His heart will also have become stronger as well. 

Week 9 

During this week, the baby's reproductive organs begin to form. The baby's size is doubled in form. The tips of the fingers are visible, and the size of the head is about half the length of the total body length. 

Week 10 

At week 10, that the embryo stage comes to an end. Many changes occur such as the formation of fingers and toes from the paddle-like structures. The brain neurons are developing at a rate of 250,000 neurons per minute! Then end this embryonic stage will mark an end of a dangerous stage for the baby's development. 

Week 11 

Week 11 is the time that the lungs are developing. The baby breathes in and out amniotic fluids. The ear lobes are also forming at this stage. 

Week 12 

The baby's sense of feel and touch are developing at this stage, and it can sense a touch on the womb. The muscles are also developing, and the baby regularly kicks and wiggles. You cannot feel it because the baby is still small. 

Week 13 

All the essential organs of the baby have formed. The unborn baby is growing at a high rate. The eyes, ears, and arms are starting to look proportionate. The unborn baby can put a thumb in his mouth. The legs need some time to grow as well. 

Week 14 

During week 14, the roof of the baby's mouth forms, the cheeks are also forming as he learns to suck. Boys develop the prostate at this stage, while girls develop the ovaries. 

Week 15 

At this stage, the baby will be covered with downy hair to help in preserving body heat. The facial muscles will also be flexing, (not indicative of emotion) as they develop. 

Week 16 

During this week, the bones are hardening, and the umbilical cord is fully matured. The baby girl has hundreds of eggs forming inside her ovary; they will become your grandchildren! 

Week 17 

The placenta is now the same size as the baby, nourishing it and carrying away waste. The body of the baby is now fully proportionate. The baby's sweat grand are also developing at this stage. 

Week 18 

The baby now can hear every sound around her. Sudden noises loud noises can startle the baby. Speak to the baby to help her to recognize your voice. 

Week 19 

At this stage, the body will begin to get a white greasy coating called the Vernix Caseosa. The baby's heartbeat will also be growing stronger by the day. 

Week 20 

The baby continues to grow and look like mom and dad every day. His or her hair and eyebrows will also be sprouting each day. 

Week 21 

The baby's stomach is now being equipped to absorb nutrients from the amniotic fluid the baby is swallowing. Most of the nutrients are still coming in through the placenta. 

Week 22 

The baby starts to feel anything they can touch. Their skin also begins to darken and for some, hair grows on their scalp. 

Week 23 

The bay's brain cells will start forming, starting from now to help the baby live normally. The lungs are also going to fully mature this week in readiness for the baby to breathe air. 

Week 24 

The baby now responds fully to touch and sound. The baby at this stage can also tell if it is upside down. Movement at this stage has a meaning to the baby. 

Week 25 

The baby forms poop called the meconium inside its large intestine which is excreted shortly after birth. If it is excreted before birth, then it must be sanctioned out of the lungs. 

Week 26 

The baby now has distinct sleep-wake patterns, noticed by the alternating calm and kicking sessions. The sleep and wake patterns maybe like yours. 

Week 27 

At this stage, the baby may get hiccups, seen as belly jumps. The baby's trachea is filled with amniotic fluid, so you will not hear a sound. 

Week 28 

The baby will now be able to open his eyelids. The baby will also have some color pigmentation in his eyes. 

Week 29 

The baby's brain becomes complex, and his becomes body stronger. You will be able to get instant reactions to stuff like sound, light, and food. 

Week 30 

The baby makes less movement because of less room to maneuver; you should contact a health provider is you do not feel any motion. The fewer movements are because he is adding weight in the form of fats and flesh to help insulate and cushion the organs. 

Week 31 

This is the stage that the baby takes the final position of the fetus until birth. The testicles move into the scrotum if it is a boy or the clitoris forms if she is s girl. 

Week 32 

Every other organ is fully formed now, except for the lungs which need more time. The babies born at this stage will normally have a normal life. 

Week 33 

At this stage, the baby's position is affected by your daily activities such eating, talking, and resting. 

Week 34 

The body is getting covered by the protective cheese-like substance to ensure the baby's skin stays smooth. The baby is born with this substance which is later washed off during his first birth. 

Week 35 

At this point, the baby is positioned with the heading facing the cervix and vagina. If not, there is a 65% chance of the healthcare provider changing it. If not, a c-section may be needed. 

Week 36 

The baby is padding himself with fat, and his sucking muscles are fully developed. He will be born with a round face and ready to suckle. 

Week 37 

The baby can hear, and his eyes are becoming perfect each day. He or she will be able to recognize your voice when born and turn in your direction! 

Week 38 

The baby's brain is now fully functional ready to regulate breathing, blood circulation, and digestion. The baby born at this time is considered fully mature. 

Week 39