Fetal Development

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Welcome to your fetal development area! Here's where you can see what's happening with your baby week-by-week! Mouse over the images and see how your baby is growing! For an overview of all weeks, please click here.

First Trimester: Weeks 1-4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9 | Week 10 | Week 11 | Week 12 | Week 13 | Week 14
Second Trimester: Week 15 | Week 16 | Week 17 | Week 18 | Week 19 | Week 20 | Week 21 | Week 22 | Week 23 | Week 24 | Week 25 | Week 26 | Week 27
Third Trimester: Week 28 | Week 29 | Week 30 | Week 31 | Week 32 | Week 33 | Week 34 | Week 35 | Week 36 | Week 37 | Week 38 | Week 39 | Week 40

Week Five

Return to Fetal Development Overview

• First heartbeats begin - If you have an early ultrasound you may not be able to recognize this tiny being as a baby, but there is no mistaking what it feels like seeing your child's heartbeat on that screen. That rhythmic beat is echoed in your own heart.

• Umbilical cord develops - This is your baby's lifeline in utero. It bears the responsibility of pumping in oxygen, removing waste, and supplying the necessary nutrients for the remainder of your pregnancy.

• Blood is now pumping - All four heart chambers are now functioning, insuring your baby's body will receive all it needs over not only the remainder of your pregnancy but throughout life.

• Most other organs begin to develop - Your infant's lungs start to appear, along with her brain. Already your little one is preparing for a quest for lifelong learning!

• Arm and leg buds appear - While they may not appear to be much at this stage it is ok to dream of the future. Just imagine your ballerina twirling and jumping around your kitchen floor. Or perhaps you will have the precocious boy that throws the perfect pitch -- right through the neighbor's window.

3d ultrasound images reprinted with permission from Eco-3d and SonoPortal. Embryoscopy and fetoscopy photos appearing on this web site are reproduced under "fair use" uterms for the purpose of public education.

It's simply amazing! There simply is not another word worthy to describe the development of your baby! Just think, within approximately a 40 week period, your little one will have transformed from a single cell to a fully formed human -- filled by wonderment and prepared to change your world forever. For an overview of fetal development, you can click here.

The first trimester (0 - 14 weeks), is one of the most crucial for your baby. Within this trimester you will find the most rapid rate of growth and development taking place. By the end of the 1st trimester, your son or daughter will have grown to 3.4 inches (8.7 cm) long and weigh about 1.5 ounces (43 grams). Your infant will develop everything from limbs to vital organs. Week by week the changes are astounding!

Your rate of growth in the second trimester is nothing compared to the baby's. If this rate of growth continued after birth, he or she would be thirteen feet tall at one month of age! Did you know all of baby's major organs have formed by the 15th week of pregnancy? Some, such as the heart and kidneys, will continue to develop further this trimester. Eyebrows and fingernails form. The reddish, wrinkled skin is covered with a fine hair. By the end of this trimester your baby is between 11 and 14 inches long and weighs about 2 to 2½ pounds. She can swallow and hear. You will notice periods of activity and quiet as he moves, kicks, sleeps and wakes.

By the beginning of this trimester your baby will have all of his/her bones -- 300 to be exact! Now he'll be building fat stores and muscle mass. Your baby's hair will be growing, replacing the lanugo that protected her skin in the womb. By the end of this trimester your baby will be approximately 7 pounds in weight and about 20 inches long. Her lungs mature right up to birth so don't become too anxious to deliver early. Each day in the womb, helps prepare your little one for the world outside!

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