Fetus Growth During Pregnancy

While in the womb, a fetus goes through major growth and development over the 9 months of the pregnancy. This growth changes with each month because certain body parts develop during certain months. Using the information below, you can track the growth and development of your baby month to month from the first heartbeat to the completion of the baby.

Month One

During the first month, your fetus is little more than a pea at half an inch in size and weighs less than 1 ounce. The baby begins its life as a fertilized egg that attaches itself to the lining of the uterus. Then, the cells start to grow, forming arms, legs, heart, lungs, the brain and the spinal cord. Around the end of the month, the heart will start to beat, according to the American College of Obstetricians and Gynecologists.

Month Two

In month two, the baby grows half an inch but is still under 1 ounce in weight. Much of the body is taking shape in this month. The eyelids develop over the eyes, bones start to grow, all major organs start to form, and the inner ear, toes, fingers, wrists, internal genitals and ankles are created.

Month Three

Month three marks the end of a full trimester. With only two more trimesters to go, your fetus is 3 1/2 inches and weighs a little more than an ounce. The baby’s mouth is preparing for future teeth, and the muscles, bones, fingers, toes and skin are growing. The baby forms fingernails and intestines during this month, too.

Month Four

During month four, the baby takes a growth spurt and grows to around 6 to 7 inches and weighs 5 ounces. The baby now has eyelashes, eyebrows, external genitalia, an outer ear, neck and kidneys. Your baby can also hear and swallow.

Month Five

The baby is now 10 inches and weighs half a pound to 1 pound. The baby can now suck his thumb and sleep, and his reproductive systems are fully functional.

Month Six

In month six, the baby is growing to 12 inches and 1 to 1 1/2 pounds. Its hair is growing, is brain is developing, the eyes open and the lungs are fully formed.

The Third Trimester

During the third trimester, most of the baby’s development is complete. At seven months, most babies weigh around 2 to 2 1/2 pounds and are 14 inches long. The fetus’s eyes can see light, and she can respond to sound. By month eight, your baby should be around 18 inches long and weigh 5 pounds. The bones are hardening, and the tastes buds are forming. In the last month of pregnancy, the fetus should be around 20 inches long and weigh 6 or more pounds. The lungs are ready to start breathing finally, and the baby will move into birthing position.