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Fetus Development Chart Week by Week

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 oz

0.2 gr

6 week fetus size

0.25 inch

0.6 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 oz

0.4 gr

7 week fetus size

0.5 inch

1.3 cm

Sex cells are formed. Improved internal systems: lymphatic, circulatory, excretory, digestive. The cerebellum and pituitary gland appear.

0.05 oz

1 gr

0.65 inch

1.6 cm

Testosterone starts to be produced. Facial features appear nose, mouth, ears, and eyes. The bile ducts are formed.

0.07 oz

2 gr

1 inch

2.5 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 oz

4 gr

1.25 inch

3.2 cm

Laid internal organs. The heart is 4-chambered. The brain is divided into hemispheres. The oral cavity and rectum are formed.

0.25 oz

7 gr

1.5 inch

3.8 cm

The circulatory, digestive, and nervous systems function. Simple reflexes appear. Sexual organs are formed.

0.5 oz

15 gr

2.25 inch

6 cm

All life support systems work. The eyes are covered with eyelashes. The skin is covered with villi. Functioning intestinal peristalsis.

0.8 oz

25 gr

3 inch

8 cm

The heart muscle is actively contracting. The liver secretes bile and the thyroid gland secretes hormones. Formed lungs, bronchi, and trachea.

1.5 oz

40 gr

3.5 inch

9 cm

Reflex mimic activity grows. Subcutaneous fat develops. Developed sweat and sebaceous glands. The first meconium appears.

2.5 oz

70 gr

4 inch

10 cm

The heart pumps blood. The capillary network expands. The ossification nuclei develop. The bone marrow produces lymphocytes.

3.5 oz

100 gr

4.5 inch

12 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 oz

140 gr

5 inch

13 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 oz

170 gr

5.5 inch

14 cm

The neck is stretched. The genitals are formed and the sex can be determined. The thymus gland matures morphologically.

8 oz

225 gr

6 inch

15 cm

The endocrine glands are active. Bronchioles are formed in the bronchi. The fetus reacts to light and loud sounds.

10 oz

280 gr

10 inch

25 cm

The fetus is actively moving. The skin becomes less transparent. The muscular frame is strengthened. The lungs work in utero.

12.5 oz

350 gr

10.5 inch

27 cm

The fat layer grows. More conscious movements appear: the child rubs his eyes and sucks his thumb. The inner ear develops.

15 oz

420 gr

11 inch

28 cm

The capillary network of the skin is formed. Melanin is produced. Completely formed primordial feces (meconium).

1 lb

450 gr

11.5 inch

29 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 lb

550 gr

12 inch

30 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 lb

700 gr

13 inch

33 cm

Increased production of pulmonary surfactant. The pituitary gland produces growth hormones. Calcium accumulates inside the bone tissue.

1.75 oz

800 gr

14 inch

35 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 lb

900 gr

14.3 inch

36 cm

The ovale is open in the heart. Developed bronchial tree. The pancreas produces insulin.

2.25 oz

1 kg

14.6 inch

37 cm

Lacrimal ducts are formed. The pupillary membrane disappears from the eyeballs. Hypodermis is actively developing. The skin is smoothed out.

2.5 lb

1.2 kg

15 inch

38 cm

The nasal bone is well formed. The baby opens and closes his eyes. The iris of the eye is formed.

3 lb

1.4 kg

15.5 inch

40 cm

New convolutions and grooves appear in the brain. The temporal lobes of the brain are developed. The skin acquires pigment.

3.25 lb

1.5 kg

16 inch

41 cm

The brain develops intensively: protective membranes and cortex appear. Nerve impulses are rapidly transmitted.

3.75 lb

1.7 kg

16.5 inch

42 cm

The child is fully formed but still weak. Maintains muscle tone. The immune system improves.

4.25 lb

1.9 kg

17 inch

43 cm

Structurally improved brain. The cerebellum and pituitary gland work. Neural connections are formed. The child can maintain balance.

4.75 lb

1.9 kg

17.5 inch

45 cm

The child is in a prenatal position. The digestive system is mature. Well-developed reflexes. Sufficient pulmonary surfactant accumulated.

5 lb

2.3 kg

18 inch

46 cm

Beklar's nuclei (ossification nuclei) are well formed. Subcutaneous fat accumulates for full thermoregulation. The placenta reaches maturity.

5.75 lb

2.6 kg

18.5 inch

47 cm

Well-developed inner ear. Cartilage and bones get stronger. Gastric juice is secreted. The pancreas produces enzymes.

6.25 lb

2.8 kg

19 inch

48 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 lb

3.1 kg

19.5 inch

49 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 lb

3.3 kg

20 inch

50 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 lb

3.5 kg

20.2 inch

51 cm

The baby is completely ready for birth. All vital organs and systems are formed and developed.

7.85 lb

3.5 kg

20.4 inch

52 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.


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.

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