Pay Your BillGuide for a Healthy Pregnancy
PREGNANCY TESTS AND SCREENINGS
If You Are Rh Negative
Everyone has one of four major blood types. You have either type A, B, AB, or O blood. The type of antigens on your bloods cells determines the type of blood you have. Antigens are proteins on the surface of blood cells that can cause a response from your immune system. If your blood has the Rh antigen, you are Rh positive. If your blood doesn’t, you are Rh negative. Most people are Rh positive.
Rh negativity occurs mostly among Caucasians. 15% of Caucasians are Rh negative.
If you are Rh negative and your baby’s father is Rh positive, your baby has a chance of being Rh positive. Problems may occur when the mother’s blood is Rh negative while the fetus is positive. This situation is called Rh incompatibility. Sometimes the fetus’s blood mixes with yours and your body may respond as if it were allergic to your fetus. Your body may produce antibodies in response to the Rh antigens in your fetus’s blood (a process called sensitization). This can cause anemia and possibly severe illness or even death for your fetus.
A routine blood test can be done to identify women at risk for Rh incompatibility. Sensitization can be prevented most of the time. Your doctor can prescribe shots that prevent you from forming antibodies. A blood product called Rhogam is injected into your arm or buttocks. This will prevent you from responding to your baby’s Rh-positive red blood cells. This is generally given during your 28th week. This treatment is good only for approximately 12 weeks. After your child is born, you will be given Rhogam if your baby is Rh positive. Rhogam is also given at the time of amniocentesis or when Rh negative woman is bleeding during pregnancy because there is a potential that the mother’s and baby’s blood might mix and cause an allergic reaction to the baby.
Cystic Fibrosis
What is Cystic Fibrosis?
Cystic fibrosis (CF) is one of the most common inherited diseases that occurs in about 1/1600-1/2500 Caucasian babies in the United States. It can occur in other ethnic groups such as Native Americans (1/4000), Hispanics (1/8000), African-Americans (1/15,000 and Asians (1/32,000), but it is much less common. It occurs equally in boys and girls.
CF causes chronic lung and digestive system problems, the severity of which can vary, and at present, cannot be predicted. CF can also affect the sweat glands, pancreas and liver. Abnormal levels of salt are excreted from the sweat glands. CF is usually diagnosed in early childhood by a laboratory test called a “sweat test” which can detect abnormally high levels of salt (sodium and chloride).
There is currently no cure for CF, as there is no specific way to correct the genetic abnormality, although gene therapy is currently being investigated. Current medical treatment is aimed at reducing symptoms and prolonging life. Many children with CF are chronically ill and need frequent clinic visits and hospitalization.
The life expectancy of children with CF has improved greatly in the past 20 years. In the recent past, the average life span was 28 years. At present, it is predicted that the average life expectancy is nearer to 40 years. This would have been thought to be impossible several years ago. Yet, many children still die at a young age due to the severity of the disease, even with the best of care at specialized CF centers.
How is cystic fibrosis inherited?
Cystic fibrosis occurs when a child inherits two cystic fibrosis genes, one from each parent. This type of inheritance is called autosomal recessive. If the parents of a CF child are not affected with CF themselves, then they carry one CF gene and one normal gene and are considered CF carriers.
When both parents carry a CF gene, there is a 1 in 4 (25%) chance with each pregnancy that they could pass on a copy of the CF gene and have a child affected with CF. There is a 2 in 4 (50%) chance with each pregnancy of having a child who is a CF carrier like themselves, and a 1 in 4 chance that the child will inherit two normal genes and not be a carrier or be affected with CF.
What is cystic fibrosis carrier testing?
In the United States today, about 1 in 25 Caucasians, 1 in 32 Native Americans, 1 in 45 Hispanics, and 1 in 65 African Americans are carriers. Individuals who have a family history of CF, such as a sibling or first cousin with the disease, have a greater chance of being a carrier. The more closely related the relative with CF, the higher the chance of being a CF carrier.
A direct detection DNA test for CF carriers is available to identify most CF carriers. Currently, about 94 of the most common mutations are used in the DNA carrier test. Accuracy of carrier testing for someone without a family history of CF depends on a person’s ethnic background.
The following table shows the carrier frequency and detection rate of specific ethnic groups.
| Background | Carrier Frequency | Carrier Detection Rate |
|---|---|---|
| Northern European Caucasian | 1/29 | 90% |
| Southern European Caucasian | 1/29 | 74% |
| Ashkenazi Jewish Caucasian | 1/29 | 97% |
| Hispanic | 1/46 | 62-85% |
| African-American | 1/65 | 60-80% |
| Asian | 1/90 | 38% |
| Native American | 1/52 | 81% |
CF carrier test results are very accurate (>99%) if an individual is found to carry a CF mutation. If an individual is negative for these mutations, then the accuracy of the test results is dependent on correct knowledge of the affected family member’s mutation status, the ethnic background of the family, and correct representation of a family structure in a family with CF. Given that the detection is less than 100%, there is still a small chance of having a child with CF for a couple with negative CF carrier test results.
Who should have cystic fibrosis carrier testing?
Individuals who should consider carrier testing include:
- Those who have a relative with CF.
- Those who have a spouse with a positive family history of CF.
- Those who are concerned about CF who are planning a pregnancy or who are in the early stages of pregnancy.
Prior to requesting carrier testing, individuals or couples should think about what they would do if they are found to be a carrier of CF. For example, would a couple wish to pursue prenatal diagnosis for CF during a pregnancy, or would they think about adoption or sperm or egg donation to reduce the risk of having a child with CF. Some couples may decide to not have carrier testing and wait till birth when newborn screening for CF is done. Carrier testing is best done before getting pregnant, allowing time for additional family studies, if required, and for consideration of reproductive options. Carrier testing can be done during a pregnancy, but should be performed early in order to allow time for prenatal diagnosis if it is desired.
Down Syndrome Testing
Down syndrome (Trisomy 21) is a disorder where all of the cells in the body carry an extra copy of chromosome 21. It is the most common chromosomal disorder. Individuals with Down syndrome have typical physical features, mental retardation, and often have heart and intestinal abnormalities. The risk of delivering a baby with Down syndrome increases as a woman ages, but there is some chance of Down syndrome at any age. There are several options we offer to test for Down syndrome.
| Option | Consists of | Advantages | Disadvantages | Best for |
|---|---|---|---|---|
| No Down Syndrome Testing | No anxiety due to false positive results | Women who would not consider further testing or pregnancy termination | ||
| Invasive Testing: Amniocentesis**
(Amnio) CVS** |
Inserting a needle into the amniotic sac at 16-20 weeks gestation Inserting a needle into the placenta at 11-13 weeks |
99% detection of Down syndrome 99% detection of Down syndrome |
About 1/300 risk of miscarriage About 1/100 risk of miscarriage |
Women who want definitive diagnosis of Down syndrome Women who want the most definitive diagnosis of Down syndrome earlier than 17 weeks |
| First trimester screen** |
|
Not invasive 80% detection of Down syndrome |
5% false positive (1/20 women will be told the risk of DS is increased and would need amnio or CVS for definitive diagnosis) | Women who want to screen for Down syndrome but do not want invasive testing |
| Serial/Sequential Testing** |
|
Not invasive 90.4% detection of Down syndrome 90% detection for trisomy18, 80% detection for neural tube defects |
Results of first trimester not available until second trimester testing is completed (unless Down syndrome risk is >1/25). 2.5% false positive (1/40 women will be told the risk of Down syndrome is increased and would need amniocentesis for definitive diagnosis). | Women who want the higher detection rate for Down syndrome, do not want invasive testing, and can wait until 18 weeks for the combined results. |
| Integrated Screen |
|
Not invasive 92% detection of Down syndrome 90% detection for trisomy18, 80% detection for neural tube defects |
Results of first trimester not available until second trimester testing is completed. 2.5% false positive (1/40 women will be told the risk of DS is increased and would need amniocentesis for definitive diagnosis). | |
| Maternal Serum AFP-4* |
Maternal blood test measuring 4 proteins done at 16-20 weeks | Not invasive 81% detection of Down syndrome, trisomy 18, and neural tube defects |
5% false positive (1/20 women may be told the risk of DS is increased and amniocentesis recommended for definitive diagnosis). | Women who want to screen Down syndrome but do not want invasive testing |
| Genetic Ultrasound | Ultrasound done at 16-20 weeks looking for markers associated with DS | Not invasive 70% detection of Down syndrome |
8-12% false positive (the risk of Down syndrome is increased and amniocentesis is needed for definitive diagnosis). |
Women who want to screen for Down syndrome but do not want invasive testing |
*Covered by all insurance. **Not covered by all insurance for women less than 35 years old.
Diabetes Screening
Diabetes
Diabetes is a disease that about 1 in 100 women have. Women with diabetes typically have healthy pregnancies. This is because many things can be done to keep blood glucose levels in check. With care and advising from your healthcare team, many of the related risks associated with the disease including miscarriage, birth defects, pregnancy-induced hypertension, hydramnios, macrosomia, still birth, and respiratory distress syndrome can be reduced.
Some of the things you can do to keep diabetes under control include:
- Watching your diet
- Exercising
- Taking insulin (if prescribed)
- Monitoring your blood glucose levels
Gestational Diabetes
Pregnancy can change the way your body handles sugar. Some women develop a sugar intolerance called gestational diabetes. Gestational diabetes results from hormones made by the placenta that alter the way insulin works. A woman who has gestational diabetes has a high risk of developing diabetes later in life.
Almost half of the women who develop gestational diabetes do not have known risk factors. Women who
may be at higher risk include:
- Women older than 30 years old
- Obese women
- Women who have had large babies (over 9 lbs.)
- Women with a family history of diabetes
- Women of an ethnic group with a high rate of the disease
Often there are no symptoms with gestational diabetes. Clinicians test all women for this problem between the 24th and 28th week of pregnancy. When you go to the lab for your test, you will drink a sweet liquid and have a blood test one hour later. You should not have anything sweet or starchy (like bagels or potatoes) for two hours before the test.
One in seven women have an abnormal test result, but not all of them will have gestational diabetes. A three-hour follow-up test is done to confirm diabetes. If you do have it, you may need to change your diet and exercise. You may also need to check your blood sugar daily to prevent problems. Some women need to take insulin too during their pregnancies.
If diabetes is not controlled, your baby has increased odds of macrosomia. Babies with macrosomia are overly large and often have health problems including low glucose levels, low blood calcium and magnesium levels, too many red blood cells, jaundice, and breathing problems. However, with modern methods such as monitoring and what science has learned about diet, this can often be prevented by collaboration between the pregnant mother and her clinician.
On the day of testing, don’t eat for 2 hours prior to coming in for your test. Go directly to the lab to receive a sugary drink. You will be tested one hour after you ingest the drink.
Group B Strep (GBS)
What is group B strep?
Group B strep (GBS or group B streptococcus) is a common germ. It is found in the world around us and sometimes in our bodies. Women may have it in their intestinal tracts and vaginas.
Healthy people who have this germ are called GBS carriers. They have no symptoms of GBS. While GBS does not make carriers sick, it can cause illness in some people – especially newborn babies. GBS is the most common cause of life-threatening infections in newborns.
Why is GBS important in pregnancy?
Between 10-30% of pregnant women have GBS. Most are healthy carriers with no symptoms. But if you carry GBS, you can give it to your baby. Usually this happens during birth.
Approximately one of every 100 to 200 babies whose mothers carry GBS develops symptoms of the disease. Most of the time, cases among newborn babies occur within the first week of life. Most newborns are not harmed by GBS. Typical problems associated with GBS disease include pneumonia, a blood infection, or meningitis (an infection of the fluid and lining around the brain). Babies who get GBS disease are treated with antibiotics for several days. Many do very well, but some have serious health problems. Rarely, they even die.
GBS can make the mother sick after birth too. Generally, though, GBS disease is less serious in adults than in newborns.
Who is at higher risk for GBS disease?
Pregnant women with the following conditions are at a higher risk of having a baby with GBS disease:
- Previous baby with GBS disease
- History of urinary tract infection due to GBS
- GBS carrier late in pregnancy
- Fever during labor
- Rupture of membranes 18 hours or more before delivery
- Labor or rupture of membranes before 37 weeks
Can GBS disease in babies be prevented or treated?
- A mother who carries GBS can be treated with antibiotics during labor. The drugs are given by IV (a thin plastic tube with a needle put into a vein in your arm). This greatly reduces the already small chance that the baby will get GBS disease.
- After birth, babies at risk for GBS disease sometimes are given antibiotics by IV until tests show no more drugs are needed.
Sometimes babies get GBS even when their mothers do not have it. They can be treated with IV antibiotics too.
How can I be checked for GBS?
Your clinician can test you by taking a sample from your vagina and rectum. The specimen is sent to a lab, where it is cultured. This takes a few days. Faster tests are being developed, but are not yet reliable. A test done late in pregnancy most accurately predicts if you will be a GBS carrier at the time of labor.
Why can’t I be treated during pregnancy to cure GBS?
One in three women with GBS will always have it. In other women, GBS comes and goes. So even if it is treated, GBS may come back later. That’s why treatment works best during labor.
Talk to your clinician now about his/her strategy for preventing GBS disease in babies. While discussing the choices, think about this:
A GBS carrier with no conditions of fever during labor, rupture of membranes (water breaking) 18 hours or more before delivery, and labor or rupture of membranes before 37 weeks has the following risks:
- 1 in 200 chance of delivering a baby with GBS disease if antibiotics are not given.
- 1 in 4,000 chance of delivering a baby with GBS disease if antibiotics are given.
- 1 in 10 chance, or lower, of experiencing a mild allergic reaction to penicillin (such as rash).
- 1 in 10,000 chance of developing a severe allergic reaction called anaphylaxis to penicillin.
Who should receive antibiotics for GBS?
Obstetric clinicians suggest women get tested for GBS when they are 35-37 weeks pregnant. Then during labor, they offer antibiotics to all GBS carriers.
Does this strategy work?
This cuts down on GBS disease in mothers and newborns. It is not 100% effective. Studies continue to be done on the best way to help prevent GBS in babies.
What should I do if a test shows I have GBS?
Remember, GBS disease in newborns is not common. It can often be prevented by giving mother antibiotics during labor. If a test shows you have GBS, be sure to tell the clinicians caring for you when you are in labor. This is especially important if your waters break before labor starts or early in labor.
