Mercy Health System

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How your baby grows during pregnancy

The first two weeks:

Your baby’s life and growth begin the moment a sperm joins an egg. Together the sperm and egg form one cell that divides at a rapid rate. By the end of the first week, the cluster of cells reaches the uterus where it will implant and grow. All of this has occurred even before you realize you are pregnant.

Third and fourth weeks:

Your baby’s spinal cord, brain, heart and lungs are now starting to develop. The tiny heart begins to beat. The face is beginning to form and dark circles mark where the eyes will be. The baby is about 3⁄16″ long.

Second month:

As the second month begins, your baby’s ears start to develop. Tiny buds that will grow into arms and legs start to form. The brain and spinal cord are now well-developed. The baby’s head is large compared to the rest of the body. At the end of eight weeks, your baby is about an inch long and weighs about about 1⁄30th of an ounce.

Third month:

 Your baby’s arms and feet are now fully formed. Fingernails and toenails begin to grow. The sex of the baby can now be seen and the internal sex organs are developing as well. By the end of three months, your baby is about three inches long and weighs about one ounce.

Fourth month:

Your baby’s heartbeat can be heard using a special stethoscope. The baby already has eyebrows and eyelashes and can suck her thumb. By the end of the fourth month, your baby is about seven inches long and weighs about four ounces.

Fifth month:

It is during this month that most mothers feel the baby move for the first time. This is called quickening. Your baby is busy developing muscles and exercising them. Your baby weighs from 1⁄2 to one pound and is about 10 to 12 inches long.

Sixth month:

Baby’s skin is reddish in color, wrinkled and covered with a heavy, creamy coating called vernex. Vernex protects the baby’s delicate skin. Your baby is becoming quite active and you are able to feel the baby’s movements easily. Your baby measures 11 to 14 inches long and may weigh as much as 1-1⁄2 to 2 pounds.


Seventh month:

During this month, your baby continues to grow and exercise. Your baby’s lungs are still not fully mature so if a baby is born at the end of seven months, he may need a skilled intensive care unit until he can breath without help.

Eighth month:

Your baby is getting longer and fatter. If born prematurely at the end of this eighth month, her chances for survival are good. The baby is now about 18 inches long and weighs as much as 5 pounds.

Ninth month:

During this month, your baby continues to grow and mature. His skin is still coated with vernex. His position may change as he gets ready for labor and delivery, dropping down into your pelvis in the birth position. At the end of the ninth month, an average full-term baby weighs 7 to 7-1⁄2 pounds and is about 20 inches long.

New Generations Birthing Center – Janesville

At Mercy Hospital and Trauma Center
1000 Mineral Point Ave.
Janesville, WI 53548
Driving directions
(608) 756-6000  •  (800) 756-4147


New Generations Birthing Center – Lake Geneva

At Mercy Walworth Hospital and Medical Center
Hwys. 50 and 67, N2950 State Road 67
Lake Geneva, WI 53147
Driving directions
(262) 245-0535  •  (877) 893-5503

Serving the communities of Walworth County including: Lake Geneva, Delavan, Elkhorn and Williams Bay.