First Trimester Changes -- What's Happening to You and Baby?

by Virginia B. Hargrove First Trimester ChangesUnless you share the "big news," no one would guess you're pregnant yet. What kinds of changes are your body and baby going through in the first trimester of pregnancy?

Your body's been working overtime producing hormones and extra blood cells that set the stage for your wee babe's amazing growth.

Your baby began as a single cell. By the end of the first trimester, a little face with eyelids, nose, mouth and chin peek out from the ultrasounds. Even though you don't feel anything yet, your sweet babe kicks, moves and even sucks at a thumb.

Let's take a look at what's happening inside to you and your baby during the first trimester.

First Trimester Changes

Your Body

Weeks 1 and 2: Your uterus sheds its lining and prepares to make a new one that's ready to nourish a fertilized egg. At the same time eggs ripen inside follicles. One (or more for some multiple births) of those follicles develops, ovulates and bursts, allowing the egg to start its trip down your fallopean tube, typically between days 14 and 17.

Week 3: Your fertilized egg continues moving down the fallopian tube, growing larger as cells divide.

Week 4: As your wee babe burrows into your uterine lining, you might experience a small amount of bleeding. That's normal. Your baby's cells and the placental tissues continue to grow, establishing a connection with your blood supply.

Week 5: A late period might be your first sign of pregnancy. Soon after your missed period, you may notice your breasts feel sore, you're using the bathroom more often and you're more tired than usual.

Weeks 6 to 12: Your body isn't changing the way you might have imagined, but you feel like something's going on. You might use words like heavy, thick or tight to describe how your uterus feels.

By the end of the first trimester, your womb expands and reaches half way to your belly button.

Your Baby in the Womb

Weeks 2 and 3: Your baby grows from an egg cell and a tidy batch of genetic material from the sperm to a solid ball of several hundred cells. The embryo cruises down the fallopian tube and enters the uterus about four days after conception. Usually, the tiny ball of cells bounces around the uterus a few days, finding a suitable spot to implant in the lining.

Week 4: Although your baby is still a microscopic cluster of cells, three different layer are forming. They'll become the nervous system, the GI tract and your baby's skeleton, muscles and blood system.

Week 5: Your baby looks less like a ball and more like a curled tube. One end becomes your baby's head; the other the bottom. Between the two ends, the spinal cord forms. The heart looks like a primitive tube. Other major organs begin developing rapidly this week.

Week 6: Almost a half inch long, your baby's arm and leg buds begin to lengthen. A nose shows and the eyes even have lenses. The heart begins thumping and by the end of the week, beats about 150 to 160 times each minute. The spine is completely formed and closes at both ends.

Week 7: Your baby's brain blasts off. New nerve cells form at the rate of 100,000 per minute. They'll branch out and connect, forming the first primitive pathways for baby's central nervous system. On other fronts, the heart tube forms bulges, your baby's limb have joints and outer ears begin to take shape.

Week 8: At the end of the second month, your baby weighs in at a fraction of an ounce and is less than inch long. Within that tiny body, you'll find the major organs nearly complete. Your baby looks like a miniature human being and has graduated from embryo to fetus.

Week 9: The nerves and muscles work together now. Your baby can even bend an arm. You can't feel these small movements...yet. The arms and legs lengthen and tiny fingers and toes appear. Organs begin functioning already!

Week 10: Your baby's nearly two inches long. If you could look inside, you'd even see ankles and wrists. Several more organs begin functioning this week including the thyroid gland and gall bladder.

Week 11: Your baby has already developed sleeping and waking cycles, usually between 5 and 10 minutes long. The body and limbs are catching up with the head. Your little babe looks more like a tiny person. The organs finalize shapes and functions, glands pump out hormones and intestines form. The skin thickens and tiny hair follicles appear. Vocal cords begin forming, too.

Week 12: All major organ systems have finished developing. Now they just need to grow. Your baby will be about three inches long. The nose, eyelids and ears are in place. Some researchers say they can detect variations in personality even this early, like whether your baby will be calm or active, a thumb sucker or not.

What kinds of experiences are you going through? Did you know all these things were happening?