American Medical Association Family Medical Guide - American Medical Association [279]
CVS
In CVS, a thin tube called a catheter is inserted through the vagina into the uterus. (An alternative method is to insert a hollow needle through the abdomen into the uterus.) A syringe attached to the catheter is used to withdraw a small sample of tissue containing chorionic villi (small, fingerlike projections) from the placenta. The path of the catheter or needle is guided by ultrasound. The vagina is held open with a vaginal speculum.
Glucose Screening Test
Glucose screening is offered to all pregnant women during pregnancy, usually between the 24th and 28th weeks, to screen for gestational diabetes (see page 521), a form of diabetes that develops during pregnancy and goes away after delivery. With early diagnosis and careful control of blood glucose during pregnancy, gestational diabetes seldom causes problems for either the pregnant woman or the fetus. Untreated, however, the condition can cause the fetus to be larger than normal (resulting in a more complicated delivery) or to have a low glucose level and chemical imbalances after delivery.
During glucose screening, you are given a glucose solution to drink, and a blood sample is taken 1 hour later. If the test shows that your glucose level is elevated, you will have another, more accurate test called the glucose tolerance test (see page 895) to make a diagnosis.
Group B Strep Test
Most pregnant women are screened for group B streptococcal bacteria that live in the reproductive and urinary systems and seldom cause symptoms. However, during pregnancy, the bacteria can cause infections in the woman’s urinary tract and uterus, which, if transmitted to the baby during delivery, can cause serious complications such as pneumonia, blood infection, or inflammation of the membranes covering the brain (meningitis; see page 692). For the group B strep test, the doctor uses a swab to take a sample from the woman’s vagina and rectum. The sample is sent to the laboratory, and the cells are grown and tested for the presence of the bacteria. Test results are available within 24 to 48 hours. If you are found to carry the bacteria, you will be given antibiotics intravenously (through a vein) during labor and delivery to prevent your baby from being infected. Although one out of three pregnant women carries the bacteria, only 1 out of 200 babies actually develops an infection. The infection can usually be treated effectively by giving the baby intravenous antibiotics for about 10 days after delivery.
Fetal Monitoring
Throughout pregnancy and labor, doctors can evaluate the health of the fetus by measuring the fetal heart rate. Fetal monitoring is most frequently used during labor to make sure the fetus is getting enough oxygen and to evaluate how the fetus is reacting to the stress of labor, but sometimes is performed earlier in pregnancies considered to be high risk. For example, fetal monitoring may be performed in women who have a medical condition such as high blood pressure or diabetes, who have symptoms of preeclampsia (see page 526), or who have had a fetus die before birth (see page 530). The fetus also is monitored if fetal growth is slower than expected or if the pregnancy has passed the due date.
The simplest techniques for measuring fetal heart rate are ultrasound imaging (which provides a view of the fetus’s beating heart) or listening to the heartbeat through a type of stethoscope (called a fetoscope) placed on the women’s abdomen.
Nonstress test
A nonstress test is a noninvasive test done to evaluate the health of the fetus, usually during the last 3 to 4 months of pregnancy. Doctors measure the fetus’s heart rate as the fetus moves inside the uterus, making sure that the fetal heart rate increases in response to environmental factors, indicating that the fetus is healthy. If the fetus’s heart rate stays the same or decreases, the doctor may recommend further testing, such as a biophysical profile (see below). A nonstress test can also be used to measure the frequency of contractions later in a pregnancy.
Nonstress test
In a nonstress