Pregnancy guide to baby’s development
During pregnancy, a lot of changes happens both in the pregnant woman’s body and in the developing fetus. It is an exciting process, and if you are expecting, you are probably keen to know how the baby is developing through the stages of the pregnancy. Here, we provide you with a pregnancy guide to baby’s development during pregnancy which can help you understand how the baby grows during the three trimesters of pregnancy.
The baby’s development in the first trimester (weeks 1-12)
After fertilization, an embryo is formed. That is, two layers of cells from which all the body parts and organs will develop. The sex of the fetus is already determined at fertilization since it depends on whether the egg receives a Y or an X chromosome from the sperm cell. Though, it is first possible to detect the sex of the baby later in the pregnancy.
The first month
Within the first month of pregnancy, the fetus’ heart and lungs begin to develop. Additionally, the placenta, which is an organ that transfers nutrients from the mother to the baby, is developed. Slowly, the legs, arms, spinal cord, nerves and brain start to form. By the end of the first month of pregnancy the baby will be around 0,6 cm long – that is smaller than a grain of rice.
The second month
Entering the second month of pregnancy, the baby’s facial features is at development. Angles, wrists, fingers and eyelids begin to form, and bones appear. The genitals and inner ear are also developing. In the second month, the brain, spinal cord and nerve tissue are now well formed. Furthermore, the digestive tract and sensory organs begin their development. In the end of the second month, the baby will be about 2,5 cm long.
The third month
Now the baby’s arms, fingers, hands, feet and toes are fully formed, and the baby can open and close its fists and mouth. The teeth are beginning to form, and fingernails and toenails are beginning to develop. The external ears are also formed in the third month.
By the end of the first trimester, the baby is fully formed. Additionally, all of the baby’s organs and extremities are present and will continue to develop throughout the rest of the pregnancy. The baby is now about 4,5 cm long – about the size of a plum.
By the end of the first trimester or the beginning of the second trimester, between weeks 9 and 13, it is time for nuchal translucency scanning where the baby is examined for chromosome disorders and the date of birth is determined. (The number and timing of the ultrasound scans may vary from country to country)
The baby’s development in the second trimester (weeks 13-27)
During the second trimester, the baby is growing a lot, and between week 18 and 22 it will be possible to detect the sex of the baby.
The fourth month
In the fourth month of pregnancy, the baby’s eyelids, eyebrows, eyelashes, nails and the neck are forming. The baby’s nervous system is beginning to function, and the reproductive organs and genitalia are fully developed. The skin of the baby will have a wrinkled appearance. The baby will also be able to start bending its arms and legs, and the kidneys start to work. The baby can also hear and swallow. By the end of the fourth month, the baby will be about 15 cm long.
The fifth month
During the fifth month of pregnancy, the baby is starting to develop muscles and exercising them by getting more active and it might be possible to feel movements. Additionally, the baby starts to have a regular sleep/wake cycle, and the hair begins to grow on the baby’s head. By the end of the fifth month, the baby will be about 25 cm long and weighs between 225 and 450 grams.
Around weeks 18-22 it is time for the second ultrasound scan of the baby. Here focus is on the baby’s organs, how the baby is growing and the placenta’s position in the uterus. It is also during this scan that it might be possible to detect the sex of the baby.
The sixth month
Now the baby’s skin is wrinkled with a reddish colour. The veins are visible through the baby’s skin. The finger and toe prints of the baby are also visible. The baby is starting to respond to sounds by increasing the pulse or by moving, and the eyelids begin to part so the eyes can open. The brain is developing rapidly. The baby is now about 30 cm long and weighs about 900 grams – about the size of a cauliflower.
The baby’s development in the third trimester (weeks 28-40)
In the third trimester, the baby grows about 200-250 grams per week. The baby is slowly preparing for the life outside the placenta by practicing sucking and sinking.
The seventh month
In the seventh month, the baby is continuously maturing and developing reserves of body fat. Now the baby’s hearing is fully developed, and the baby can change position frequently and respond to stimuli like light, sound and pain. At the end of the seventh month the baby is about 30 cm long and weighs between 900 and 1800 grams.
The eighth month
During the eighth month of pregnancy, the baby is quickly gaining weight. The bones are hardening, but the baby’s skull will remain soft and flexible in order to make the delivery easier. The brain system is still developing rapidly, and different regions of the brain are forming. Most of the baby’s internal systems are well developed, but the lungs can still be immature. The baby is now about 45 cm long and can weigh up to about 2200 grams.
The ninth month
Now it is time for the final spurt before the baby is ready to say hello to the world. In the ninth and last month of pregnancy, the baby is getting ready for birth by moving down in the woman’s pelvis, usually in a head-down position. Also, the lungs are matured and prepared for functioning on their own. During the ninth month, the baby continues to gain weight rapidly. The baby is also learning how to coordinate its reflexes so he or she can close the eyes, blink, grasp firmly, turn the head and respond to stimuli like light, touch and sounds – he or she is definitely getting ready to come out. The average baby is about 51 cm long and weighs about 3500-3700 grams when he or she is born.
Remember, every pregnancy is different from one another and it is very common to go past the due date of birth. Some babies are smaller when they are born, and some are bigger. Always consult with your doctor during pregnancy, if you have any questions or concerns, and lastly, remember to enjoy every step of the journey!
Did you like this pregnancy guide to baby’s development? You may also like our post about the bodily changes during pregnancy.