A woman’s pregnancy begins from the moment the egg is fertilized. The further development of the embryo, which after the 8th week is called the fetus, will proceed at an extremely rapid pace. Every week there is new progress in development, complex reorganization of cells, and improvement of internal organs.
Having information about what exactly happens in each week of pregnancy will help to avoid unnecessary excitement. A woman experiences less stress and quickly gets used to her position knowing how her baby grows.
We provide accurate data on the parameters of the fetus at a certain stage of its intrauterine life. This article contains a summary of each week of pregnancy. A woman will be able to follow the development of the child until the very birth using this information.
| Week # | Average Weight | Similar Shape | Average Size | Development |
|---|---|---|---|---|
0.01 oz0.2 gr |
|
0.25 inch0.6 cm |
The embryo looks like a tadpole. The nervous system progresses and the brain is formed. There is an intensive development of the skeleton. |
|
0.025 oz0.4 gr |
|
0.5 inch1.3 cm |
Sex cells are formed. Improved internal systems: lymphatic, circulatory, excretory, digestive. The cerebellum and pituitary gland appear. |
|
0.05 oz1 gr |
|
0.65 inch1.6 cm |
Testosterone starts to be produced. Facial features appear nose, mouth, ears, and eyes. The bile ducts are formed. |
|
0.07 oz2 gr |
|
1 inch2.5 cm |
Parts of the body of the fetus are formed: head, trunk, and limbs. The volume of the chest and abdominal cavity increases. |
|
0.15 oz4 gr |
|
1.25 inch3.2 cm |
Laid internal organs. The heart is 4-chambered. The brain is divided into hemispheres. The oral cavity and rectum are formed. |
|
0.25 oz7 gr |
|
1.5 inch3.8 cm |
The circulatory, digestive, and nervous systems function. Simple reflexes appear. Sexual organs are formed. |
|
0.5 oz15 gr |
|
2.25 inch6 cm |
All life support systems work. The eyes are covered with eyelashes. The skin is covered with villi. Functioning intestinal peristalsis. |
|
0.8 oz25 gr |
|
3 inch8 cm |
The heart muscle is actively contracting. The liver secretes bile and the thyroid gland secretes hormones. Formed lungs, bronchi, and trachea. |
|
1.5 oz40 gr |
|
3.5 inch9 cm |
Reflex mimic activity grows. Subcutaneous fat develops. Developed sweat and sebaceous glands. The first meconium appears. |
|
2.5 oz70 gr |
|
4 inch10 cm |
The heart pumps blood. The capillary network expands. The ossification nuclei develop. The bone marrow produces lymphocytes. |
|
3.5 oz100 gr |
|
4.5 inch12 cm |
The composition of the blood is drawn up: lymphocytes, platelets, leukocytes, and erythrocytes. "Fetal" hemoglobin appears. Muscles get stronger. The baby starts blinking. |
|
5 oz140 gr |
|
5 inch13 cm |
The proportions of the body were harmonized. Nails and rudiments of teeth appeared. The skin is coated with a protective lubricant. The fetus hears sounds. |
|
6.5 oz170 gr |
|
5.5 inch14 cm |
The neck is stretched. The genitals are formed and the sex can be determined. The thymus gland matures morphologically. |
|
8 oz225 gr |
|
6 inch15 cm |
The endocrine glands are active. Bronchioles are formed in the bronchi. The fetus reacts to light and loud sounds. |
|
10 oz280 gr |
|
10 inch25 cm |
The fetus is actively moving. The skin becomes less transparent. The muscular frame is strengthened. The lungs work in utero. |
|
12.5 oz350 gr |
|
10.5 inch27 cm |
The fat layer grows. More conscious movements appear: the child rubs his eyes and sucks his thumb. The inner ear develops. |
|
15 oz420 gr |
|
11 inch28 cm |
The capillary network of the skin is formed. Melanin is produced. Completely formed primordial feces (meconium). |
|
1 lb450 gr |
|
11.5 inch29 cm |
There is a process of formation of alveoli in the lungs. Pulmonary surfactant appears. The skin ceases to be transparent and wrinkled. |
|
1.25 lb550 gr |
|
12 inch30 cm |
The sense organs are well developed. The organs are responsible for the production of hormone function: the thyroid gland, adrenal glands, and pancreas. |
|
1.5 lb700 gr |
|
13 inch33 cm |
Increased production of pulmonary surfactant. The pituitary gland produces growth hormones. Calcium accumulates inside the bone tissue. |
|
1.75 oz800 gr |
|
14 inch35 cm |
The skin hairline is gone. The volume of the brain increases and a connection is established with the adrenal cortex. Corticoids are produced. |
|
2 lb900 gr |
|
14.3 inch36 cm |
The ovale is open in the heart. Developed bronchial tree. The pancreas produces insulin. |
|
2.25 oz1 kg |
|
14.6 inch37 cm |
Lacrimal ducts are formed. The pupillary membrane disappears from the eyeballs. Hypodermis is actively developing. The skin is smoothed out. |
|
2.5 lb1.2 kg |
|
15 inch38 cm |
The nasal bone is well formed. The baby opens and closes his eyes. The iris of the eye is formed. |
|
3 lb1.4 kg |
|
15.5 inch40 cm |
New convolutions and grooves appear in the brain. The temporal lobes of the brain are developed. The skin acquires pigment. |
|
3.25 lb1.5 kg |
|
16 inch41 cm |
The brain develops intensively: protective membranes and cortex appear. Nerve impulses are rapidly transmitted. |
|
3.75 lb1.7 kg |
|
16.5 inch42 cm |
The child is fully formed but still weak. Maintains muscle tone. The immune system improves. |
|
4.25 lb1.9 kg |
|
17 inch43 cm |
Structurally improved brain. The cerebellum and pituitary gland work. Neural connections are formed. The child can maintain balance. |
|
4.75 lb1.9 kg |
|
17.5 inch45 cm |
The child is in a prenatal position. The digestive system is mature. Well-developed reflexes. Sufficient pulmonary surfactant accumulated. |
|
5 lb2.3 kg |
|
18 inch46 cm |
Beklar's nuclei (ossification nuclei) are well formed. Subcutaneous fat accumulates for full thermoregulation. The placenta reaches maturity. |
|
5.75 lb2.6 kg |
|
18.5 inch47 cm |
Well-developed inner ear. Cartilage and bones get stronger. Gastric juice is secreted. The pancreas produces enzymes. |
|
6.25 lb2.8 kg |
|
19 inch48 cm |
The fetus is formed and ready for birth. The nerves are covered with a protective sheath. Cartilage tissue is dense and elastic. |
|
6.75 lb3.1 kg |
|
19.5 inch49 cm |
The child is well developed. Alveoli formed. They are coated with a surfactant. The baby will be able to breathe. The placenta begins to age. |
|
7.25 lb3.3 kg |
|
20 inch50 cm |
Sucking and swallowing reflexes are developed. The spinal cord and part of the facial nerve have matured. The bones of the skull are soft. |
|
7.75 lb3.5 kg |
|
20.2 inch51 cm |
The baby is completely ready for birth. All vital organs and systems are formed and developed. |
|
7.85 lb3.5 kg |
|
20.4 inch52 cm |
Baby is fully developed and ready for life. Inner system is complete. |
Any statistical parameters of intrauterine development of a child are relative. Do not be upset if your baby does not meet accepted standards. All children are individuals in their genetic program. Much depends on your lifestyle during gestation and nutritional habits.
Always contact your doctor if you have any questions. Go through the examinations in time and consult with specialists.
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For more detailed information please visit our website. Here you will find everything you need to know about the stages of development in each week of pregnancy. We describe in detail all the subtleties of gestation, symptoms, and the specifics of fetal development. Our resource is formed exclusively from reliable sources.
