M2: Development of a baby during pregnancy

DEVELOPMENT OF A BABY DURING PREGNANCY

1ST week of pregnancy is actually still a menstrual cycle. The pregnancy officially begins from the first day of your last menstrual bleeding.
2nd week of pregnancy – fertilization is happening in this week. The fertilized egg is splitting in two 30 hours after fertilization. It continues to split and slowly moves toward the uterus. After splitting to more than 32 sections, the cell is called morula (i.e., raspberry)
3rd week of pregnancy – You are still not aware of being pregnant. The cell is attached to the uterus wall and it is now called a blastocyst. It is very small.
4th week of pregnancy – An embryo is formed and your body produces choriogonadotropin (HCG) – a hormone that indicates pregnancy, so if you take a pregnancy test, it may be positive.
5th week of pregnancy – A nervous system, muscles and bones are beginning to form.

6th week of pregnancy – The average size of an embryo in this period is 2-4 mm from its top to its thighs. Although it is still inaudible, the baby’s heart starts pulsating in this week. The digestive and respiratory systems are being formed as well as the small extensions that would later be arms and legs.
7th week of pregnancy – By the end of this week, the embryo is 5-13 mm long and weighs about 0,8 g, which is similar to a pea. Shoulders, arms, upper and lower legs are being formed. The first heart beats also happen during this week.
8th week of pregnancy – The baby is 14-20 mm long. The nose, eyelids and ears are formed. Bronchi begin to function. Arms and legs are growing. The skin is very thin.
9th week of pregnancy – Earlobes are being formed, arms and legs continue to grow and fingers and toes are developing. The baby begins to move although you do not feel it yet. You can hear the heart beats via ultrasound. In this week the baby is 22-30 mm long and weighs about 4 grams.
10th week of pregnancy – All vital organs begin to work together. The brain is developed. The baby now looks more human. It is 32-43 mm long and weighs about 7 grams.

11th week of pregnancy – From 11th to 20th week of pregnancy the baby grows very fast. The baby’s head makes approximately a half of its entire body. The outer genitals have developed at this stage but it is still early to determine baby’s sex via ultrasound. The sex can be determined by a prenatal test that can also be done in this week.
12th week of pregnancy – The baby’s facial features have been formed completely. Fingers and toes are completely separated. The guts are in the abdomen. The heart rate is speeding up. The baby is about 90 mm long.
13th week of pregnancy – The placenta is developed. Eyelids are closed, protecting the developing eyes.
14th week of pregnancy – The baby is around 100 mm long and weights 25 grams. Lanugo hair now covers baby’s body.
15th week of pregnancy – Bones continue to develop. Ovaries are formed at females. The baby is 113 mm long and weighs 49 grams.

16th week of pregnancy – The foetus begins to move; the bones continue to grow. It is 120 mm long and weighs 110 grams.
17th week of pregnancy – Subcutaneous fat tissue is being developed.
18th week of pregnancy – The baby can hear and its eyes are now developed. It weighs 140 grams.
19th week of pregnancy – The baby’s body is covered with Vernix Caseosa. The brain is now developed. The baby can suck on its thumb. It weighs 220 grams and is 14 cm long.
20th week of pregnancy – You are half-way through your pregnancy, the baby weighs 300 grams and is 20 – 25 cm long. Its hair and nails are developing.

21^st week of pregnancy – The digestive tract is developed; the baby is moving. It weighs 340 grams.
22^nd week of pregnancy – Significant growth.
23^rd week of pregnancy – The baby moves its fingers and toes. It weighs 450 – 600 grams.
24^th week of pregnancy – Lungs are developing quickly. The baby is about 30 cm long.
25^th week of pregnancy – The baby has hiccups. It weighs 650 grams.

26^th week of pregnancy – The baby weighs 850 grams now. Its eyes are opening, it blinks. The eyelashes and hair is growing.
27^th week of pregnancy – Lungs and liver are developing. The baby weighs 900 g. If the baby is born in this week, its chance of survival is 85%.
28^th week of pregnancy – The baby weighs 1200 grams and it is 35 cm long. Its fat tissue grows as well as its hair.
29^th week of pregnancy – The hormones such as androgen and estrogen, which stimulates production of prolactin in mother’s body so it begins to produce colostrum (the first milk).
30^th week of pregnancy – The baby weighs 1400 grams and it moves more actively.

31^st week of pregnancy – Urine production begins.
32^nd week of pregnancy – Fingers and toes are completely formed, as well as eyelashes, eyebrows and hair. The baby weighs 1700 grams and is about 40 cm long.
33^rd week of pregnancy – The lungs are almost mature. In this week, the baby takes position for birth.
34^th week of pregnancy – The baby grows further.
35^th week of pregnancy – The baby is well developed and its moves are more active.

36^th week of pregnancy – The baby weighs 2750 grams and it is 45 cm long.
37^th week of pregnancy – As the baby grows further it begins to produce cortisol – a hormone that contributes to lung maturation.
38^th week of pregnancy – The baby weighs 3000 grams. Testicles are dropping into scrotum in male babies and the labia minor is covered with labia major in female babies.
39_th week of pregnancy – The baby is ready to be born.
40^th week of pregnancy – Only 5% of pregnancies end within the assumed term. Babies born from 38^th to 42^nd gestation week are considered as mature newborns. They weigh 3500 grams on average and are 48 – 51 cm long.