How long does pregnancy last?
A normal pregnancy lasts about 40 weeks from the first day of your last menstrual period (LMP). Pregnancy is assumed to start 2 weeks after the first day of the LMP. Therefore, an extra 2 weeks is counted at the beginning of your pregnancy when you are not actually pregnant. Pregnancy “officially” lasts 10 months (40 weeks)—not 9 months—because of these extra weeks.
How is the length of my pregnancy measured?
Pregnancy can be divided into weeks and sometimes days. A pregnancy that is “36 and 3/7 weeks” means “36 weeks and 3 days of pregnancy.”
First trimester: 0 weeks–13 and 6/7 weeks (Months 1–3)
Second trimester: 14 and 0/7 weeks–27 and 6/7 weeks (Months 4 –7)
Third trimester: 28 and 0/7 weeks– 40 and 6/7 weeks (Months 7–9)
What is the estimated due date (EDD)?
The day your baby is due is called the estimated due date (EDD). Only about 1 in 20 women give birth on their exact due dates. Still, the EDD is useful for a number of reasons. It determines your baby’s gestational age throughout pregnancy so that the baby’s growth can be tracked. It also provides a timeline for certain tests that you will have throughout your pregnancy.
How is my EDD calculated?
Your EDD is calculated from the first day of your LMP. But when the date of the LMP is uncertain, an ultrasound exam may be done during the first trimester to estimate the due date. If you have had in vitro fertilization, the EDD is set by the age of the embryo and the date that the embryo is transferred to the uterus.
Why are tests done during pregnancy?
A number of lab tests are suggested for all women as part of routine prenatal care. These tests can help find conditions that can increase the risk of complications for you and your fetus.
What tests are done early in pregnancy?
- Complete blood count (CBC)
- Blood type
- Urine culture
- Hepatitis B and hepatitis C
- Sexually transmitted diseases (STDs)
- Human immunodeficiency virus (HIV)
- Tuberculosis (TB)
A CBC counts the numbers of different types of cells that make up your blood. The number of red blood cells can show whether you have a certain type of anemia. The number of white blood cells shows how many disease-fighting cells are in your blood, and the number of platelets can reveal whether you have a problem with blood clotting.
What is blood typing and what can the results show?
Results from a blood type test can show if you have the Rh factor. The Rh factor is a protein that can be present on the surface of red blood cells. Most people have the Rh factor—they are Rh positive. Others do not have the Rh factor—they are Rh negative. If your fetus is Rh positive and you are Rh negative, your body can make antibodies against the Rh factor. In a future pregnancy, these antibodies can damage the fetus’s red blood cells.
What is a urinalysis and what can the results show?
Your urine may be tested for red blood cells (to see if you have urinary tract disease), white blood cells (to see if you have a urinary tract infection), and glucose (high levels may be a sign of diabetes). The amount of protein also is measured. The protein level early in pregnancy can be compared with levels later in pregnancy. High protein levels in the urine may be a sign of preeclampsia, a serious complication that usually occurs later in pregnancy or after the baby is born.
What is a urine culture test and what can the results show?
A urine culture tests your urine for bacteria, which can be a sign of a urinary tract infection.
What is rubella and what do test results for this disease show?
Rubella (sometimes called German measles) can cause birth defects if a woman is infected during pregnancy. Your blood is tested to check whether you have had a past infection with rubella or if you have been vaccinated against this disease. If you have not had rubella previously or if you have not been vaccinated, you should avoid anyone who has the disease while you are pregnant because it is highly contagious. If you have not had the vaccine, you should get it after the baby is born, even if you are breastfeeding. You should not be vaccinated against rubella during pregnancy.
What are hepatitis B and hepatitis C and what do test results for these diseases show?
Hepatitis B and hepatitis C viruses infect the liver. Pregnant women who are infected with hepatitis B or hepatitis C virus can pass the virus to their babies. All pregnant women are tested for hepatitis B virus infection. If you have risk factors, you also may be tested for the hepatitis C virus.
Which STD tests are done in pregnant women?
All pregnant women are tested for syphilis and chlamydia early in pregnancy. Syphilis and chlamydia can cause complications for you and your baby. If you have either of these STDs, you will be treated during pregnancy and tested again to see if the treatment has worked. If you have risk factors for gonorrhea (you are aged 25 years or younger or you live in an area where gonorrhea is common), you also will be tested for this STD.
Why are all pregnant women tested for HIV?
If a pregnant woman is infected with HIV, there is a chance she can pass the virus to her baby. HIV attacks cells of the body’s immune system and causes acquired immunodeficiency syndrome (AIDS). If you are pregnant and infected with HIV, you can be given medication and take other steps that can greatly reduce the risk of passing it to your baby.
Which pregnant women should be tested for TB?
Women at high risk of TB (for example, women who are infected with HIV or who live in close contact with someone who has TB) should be tested for this infection.
What tests are performed later in pregnancy?
- A repeat CBC
- Rh antibody test
- Glucose screening test
- Group B streptococci (GBS)
If you are Rh negative, your blood will be tested for Rh antibodies between 28 weeks and 29 weeks of pregnancy. If you do not have Rh antibodies, you will receive Rh immunoglobulin. This shot prevents you from making antibodies during the rest of your pregnancy. If you have Rh antibodies, you may need special care.
What is a glucose screening test and what can the results show?
This screening test measures the level of glucose (sugar) in your blood. A high glucose level may be a sign of gestational diabetes. This test usually is done between 24 weeks and 28 weeks of pregnancy. If you have risk factors for diabetes or had gestational diabetes in a previous pregnancy, screening may be done in the first trimester of pregnancy.
What is GBS and why are pregnant women tested for it?
GBS is a type of bacteria that lives in the vagina and rectum. Many women carry GBS and do not have any symptoms. GBS can be passed to a baby during birth. Most babies who get GBS from their mothers do not have any problems. A few, however, become sick. This illness can cause serious health problems and even death in newborn babies. GBS usually can be detected with a routine screening test that is given between 35 weeks and 37 weeks of pregnancy. For this test, a swab is used to take samples from the vagina and rectum.
What happens if my GBS screening test result is positive?
If your GBS test result is positive, antibiotics can be given during labor to help prevent the baby from becoming infected.
What is the difference between screening tests and diagnostic tests for birth defects?
Screening tests are done during pregnancy to assess the risk that the fetus has certain common birth defects. A screening test cannot tell whether the baby actually has a birth defect. There is no risk to the fetus with having screening tests.
Diagnostic tests actually can detect many, but not all, birth defects caused by defects in a gene or chromosomes (see FAQ094 Genetic Disorders). Diagnostic testing may be done instead of screening if a couple has a family history of a birth defect, belongs to a certain ethnic group, or if the couple already has a child with a birth defect. Diagnostic tests also are available as a first choice for all pregnant women, including those who do not have risk factors. Some diagnostic tests carry risks, including a small risk of pregnancy loss.
What is the first step in screening for birth defects?
Screening for birth defects begins by assessing your risk factors. Early in your pregnancy, your health care provider may give you a list of questions to find out whether you have risk factors, such as a personal or family history of birth defects, belonging to certain ethnic groups, maternal age of 35 years or older, or having preexisting diabetes. In some situations, you may want to visit a genetic counselor for more detailed information about your risks.
What is a carrier test?
A carrier test can show if you or your partner carry a gene for a certain disorder, such as cystic fibrosis. Carrier tests can be done before or during pregnancy. Carrier testing often is recommended if you or your partner have a genetic disorder, have a child with a genetic disorder, have a family history of a genetic disorder, or belong to an ethnic group that has an increased risk of specific disorders. Also, cystic fibrosis carrier screening is offered to all women of reproductive age because it is one of the most common inherited disorders.
What are other types of screening tests for birth defects that can be performed during pregnancy?
Screening tests include an ultrasound exam in combination with blood tests that measure the levels of certain substances in the mother’s blood.
What are the types of diagnostic tests for birth defects that can be performed during pregnancy?
Diagnostic tests for birth defects include amniocentesis, chorionic villus sampling, and a targeted ultrasound exam.
Can I choose whether or not to have testing for birth defects?
Whether you want to be tested is a personal choice. Knowing beforehand allows the option of deciding not to continue the pregnancy. If you choose to continue the pregnancy, it can give you time to prepare for having a child with a particular disorder and to organize the medical care that your child may need. Your health care provider or a genetic counselor can discuss the options with you and help you decide.