What Happens in Each Stage of Pregnancy, First Trimester

What Happens in Each Stage of Pregnancy, First Trimester (Week 1 to the end of week 12)
Congratulations! Your journey to motherhood is underway. Check out the changes in your body and how your baby grows during the first three months.

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Changes in Your Body
During the first three months of pregnancy, or the first trimester, your body undergoes many changes. As your body adjusts to the growing baby, you may have nausea, fatigue, backaches, mood swings, and stress. These things are all normal.

Most of these discomforts will go away as your pregnancy progresses. And some women might not feel any discomfort at all! If you have been pregnant before, you might feel differently this time around. Just as each woman is different, so is each pregnancy.

As your body changes, you might need to make changes to your normal, everyday routine. Here are some of the most common changes or symptoms you might experience in the first trimester:

Many women find they're exhausted in the first trimester. Don't worry, this is normal! This is your body's way of telling you that you need more rest. After all, your body is working very hard to develop a whole new life.

Try these tips to ease exhaustion:

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Nausea and Vomiting
Usually called "morning sickness," nausea and vomiting are common during early pregnancy. For many women, though, it isn't limited to just the morning. Although it can seem like it will last forever, nausea and vomiting usually go away after the first trimester.

Try these tips to help prevent and soothe nausea:

Avoid fatty, fried, or spicy foods.

If you think you might be vomiting excessively, call your doctor. Constant nausea and/or frequent vomiting may mean you have a condition called hyperemesis gravidarum. If you lose too much fluid you might become dehydrated. Dehydration can be dangerous for you and your baby.

Frequency of Urination
Running to the bathroom all the time? Early in pregnancy, the growing uterus presses on your bladder. This causes frequent urination.

See your doctor right away if you notice pain, burning, pus or blood in your urine. You might have a urinary tract infection that needs treatment.

Weight Gain
During the first trimester, it is normal to gain only a small amount of weight, about one pound per month.

Changes in Your Baby
By the end of the first trimester, your baby is about three inches long and weighs about half an ounce. The eyes move closer together into their positions, and the ears also are in position. The liver is making bile, and the kidneys are secreting urine into the bladder. Even though you can't feel your baby move yet, your baby will move inside you in response to pushing on your abdomen.

Doctors Visits
During the early months of pregnancy, regular doctor visits (prenatal care) are especially important. Become a partner with your doctor to manage your care. Keep all of your appointments - every one is important!

During the first prenatal visit, you can expect your doctor or nurse to do the following:

For special genetic or medical reasons, you may need other lab tests, like blood or urine tests, cultures for infections, or ultrasound exams in the first trimester. Your doctor will discuss them with you during your visits.

The most common tests recommended in the first trimester include:

Nuchal translucency screening (NTS)
This new type of screening can be done between 11 and 14 weeks of pregnancy. It uses an ultrasound and blood test to calculate the risk of some birth defects. Doctors use the ultrasound exam to check the thickness of the back of the fetus' neck. They also test your blood for levels of a protein called pregnancy-associated plasma protein and a hormone called human chorionic gonadotropin (hCG). Doctors use this information to tell if the fetus has a normal or greater than normal chance of having some birth defects.

In an important recent study, NTS found 87% of cases of Down syndrome when done at 11 weeks of pregnancy. When NTS was followed by another blood test done in the second trimester (maternal serum screening test), 95% of fetuses with Down syndrome were identified.

Like all screening tests, the results are sometimes misleading. In 5% of women who have NTS, results show that their babies have a high risk of having a birth defect when they are actually healthy. This is called a false positive. To find out for sure if the fetus has a birth defect, NTS must be followed by a diagnostic test like chorionic villus sampling or amniocentesis.

NTS is not yet widely used. If you are interested in NTS, talk to your doctor. If she is unable to do the test, she can refer you to someone who can. You should also call your insurance company to find out if they cover the cost of this procedure. NTS allows women to find out early if there are potential health problems with the fetus. This may help them decide whether to have follow-up tests.

Chorionic villus sampling (CVS)
CVS is performed between 10 and 12 weeks of pregnancy. In CVS, the doctor inserts a needle through the abdomen or inserts a catheter through the cervix to reach the placenta. The doctor then takes a sample of cells from the placenta. Experts use this sample to look for problems with the baby's chromosomes. This test cannot find out whether your baby has open neural tube defects. About 1 in 200 women have a miscarriage as a result of this test.

Source: The National Women's Health Information Center
U.S. Department of Health and Human Services
Office on Women's Health

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