Pregnancy Special Checks

Special Checks

Here are a selection of optional tests used to screen for a variety of possible abnormalities.

Amniocentesis?

It is procedure in which an obstetrician withdraws a small amount of the amniotic fluid (about 20 cc) surrounding the fetus.

This is done by inserting a thin hollow needle through the mother's abdomen into the uterus. The obstetrician will use ultrasound to guide the needle during the procedure so as not to harm the unborn child.

The procedure is performed on an outpatient basis and takes only a few minutes.

The needle will ca

use some pain when it penetrates the uterus, but the pain should not last long and should not hurt more than an injection into any other part of the body.

After the fluid has been withdrawn, the removal of the needle should cause no further discomfort. The fluid is then sent to the laboratory for special tests.

Why Is Amniocentesis Necessary?
The majority of amniocentesis is done for the detection of chromosomal disorders.

Chromosomes carry genes that pass certain characteristics from parents to their children. When there are too many or too few chromosomes, or there is defect in a chromosome, birth defects usually occur.

Down Syndrome is the most common chromosomal disorder. It causes mental retardation and other health problems such as heart defects. Other less common chromosomal disorders may lead to serious handicaps and death.

When Is Amniocentesis Done?
Amniocentesis is usually done between 16th week but before the 20th week of pregnancy.

When Will The Amniocentesis Test Results Be Available?
Usually it takes about 3 - 4 weeks to complete the laboratory tests.

Can All Birth Defects Be Detected By Amniocentesis?
No. Amniocentesis can detect almost all known chromosomal disorders. However, birth defects not due to chromosomal abnormalities cannot be detected through this test.

Who Should Consider Amniocentesis?
Women who are 35 years of age or older at delivery. This is because their children are at an increased risk of chromosomal disorders such as Down Syndrome.

Women who have had a child with Down Syndrome or other chromosomal disorders.

Women who know that they or the baby's father have an unusual chromosome arrangement.

There may be other reasons that apply uniquely to you. Both you and your obstetrician should decide together if you need an amniocentesis.

Is Amniocentesis Safe?
Amniocentesis is a safe, low risk procedure when done by experienced medical experts. The risk of miscarriage following the test is reported to be 0.3 - 0.5%.

Useful Information
Activity: You should be able to return to your normal activities within a few hours after the procedure. You may have your bath as usual. Diet: There are no dietary restrictions relating to this procedure. Medication: No medication is required following this procedure.

Return To The Hospital Or Call Your Obstetrician If :

You run a fever
You feel nauseated and vomit
You experience pain in the shoulder
You experience any unusual lower abdominal pain
You notice vaginal bleeding
You notice leakage of fluid from the vagina

Chorionic Villus Sampling

It is a procedure in which an obstetrician withdraws a small amount of the placenta tissue.

This is done by inserting a biopsy needle through the mother's abdomen into the placenta. The obstetrician will use ultrasound to guide the needle during the procedure so as not to harm the unborn child. For this procedure, local anaesthesia will be given.

The procedure is performed on an outpatient basis and takes only a few minutes. The needle will cause some pain when it penetrates the uterus, but the pain should not last long and should not hurt more than an injection into any other part of the body.

After the tissue has been withdrawn, the removal of the needle should cause no further discomfort. The tissue is then sent to the laboratory for special tests.

Why Is Chorionic Villus Sampling Necessary?
Chorionic villus sampling is done for the detection of chromosomal disorders and genetic diseases such as thalassaemia.

Chromosomes carry genes that pass certain characteristics from parents to their children. When there are too many or too few chromosomes, or there is a defect in a chromosome, birth defects usually occur.

Down Syndrome is the most common chromosomal disorder. It causes mental retardation and other health problems such as heart defects. Other less common chromosomal disorders may lead to serious handicaps and death.

Thalassemia is an inherited blood disease, which is transmitted by a gene. If both parents have the thalassamia trait, the chance of having a child with thalassaemia major is 25%.

When Is Chorionic Villus Sampling Done?
Chorionic villus sampling is usually done between 10th to 12th week of pregnancy.

When Will The Chorionic Villus Sampling Test Results Be Available?
Usually it takes about 3 - 4 weeks to complete the laboratory tests.

Can All Birth Defects Be Detected By Chorionic Villus Sampling?
No. Chorionic villus sampling can detect almost all known chromosomal disorders. It can also check for specific genetic disease.

Who Should Consider Chorionic Villus Sampling?

Women who are 35 years of age or older at delivery. This because their children are at an increased risk of chromosomal disorders such as Down Syndrome.
Women who have had a child with Down Syndrome or other chromosomal disorders.
Women who know that they or the baby's father have an unusual chromosome arrangement.
If both parents are thalassaemia carriers.
There may be other reasons that apply uniquely to you. Both you and your obstetrician should decide together if you need a chorionic villus sampling.

Is Chorionic Villus Sampling Safe?
Chorionic villus sampling is a safe, low risk procedure when done by experienced medical experts. The risk of miscarriage following the test is reported to be 1%.

Useful Information
Activity: You should be able to return to your normal activities within a few hours after the procedure. You may have your bath as usual. Diet: There are no dietary restrictions relating to this procedure. Medication: No medication is required following this procedure.

Return To The Hospital Or Call Your Obstetrician If :

You run a fever
You feel nauseated and vomit
You experience pain in the shoulder
You experience any unusual lower abdominal pain
You notice vaginal bleeding
You notice leakage of fluid from the vagina

Fetal Blood Sampling

It is a procedure in which an obstetrician withdraws blood from the umbilical cord of the fetus.

This is done by inserting a thin hollow needle through the mother's abdomen into the umbilical cord. The obstetrician will use ultrasound to guide the needle during the procedure so as not to harm the unborn child.

The procedure is performed on an outpatient basis and takes only a few minutes.

The needle will cause some pain when it penetrates the uterus, but the pain should not last long and should not hurt more than an injection into any other part of the body.

After the fetal blood has been withdrawn, the removal of the needle should cause no further discomfort. The fluid is then sent to the laboratory for special tests.

Why Is Fetal Blood Sampling Necessary?
The majority of fetal blood sampling is done for the detection of chromosomal disorders, genetic diseases and viral infection.

Chromosomes carry genes that pass certain characteristics from parents to their children. When there are too many or two few chromosomes, or there is a defect in a chromosome, birth defects usually occur.

Down Syndrome is the most common chromosomal disorder. It causes mental retardation and other health problems such as heart defects. Other less common chromosomal disorders may lead to serious handicaps and death.

When Is Fetal Blood Sampling Done?
Fetal Blood Sampling is usually done between 20th and 23rd week of pregnancy.

When Will The Fetal Blood Sampling Test Results Be Available?
Usually it takes about 1 - 2 weeks to complete the laboratory test.

Can All Birth Defects Be Detected By Fetal Blood Sampling?
No. Fetal blood sampling can detect almost all known chromosomal disorders. It can also check for specific genetic disease and viral infections.

Who Should Consider Fetal Blood Sampling?

Any patient with fetal abnormalities detected during ultrasound screening.
Any patient who is more than 20 weeks pregnant and is at high risk of having a chromosomal disorder.
If both parents are thalassaemia carriers.
There may be other reasons that apply uniquely to you. Both you and your obstetrician should decide together if you need a fetal blood sampling.

Is Fetal Blood Sampling Safe?
Fetal blood sampling is a safe, low risk procedure when done by experienced medical experts. The risk of miscarriage following the test is reported to be 2 - 5%.

Useful Information
You should be able to return to your normal activities within a few hours after the procedure.
You may have your bath as usual.
Diet: There are no dietary restrictions relating to this procedure.
Medication: No medication is required following this procedure.

Return To The Hospital Or Call Your Obstetrician If :

You run a fever
You feel nauseated and vomit
You experience pain in the shoulder
You experience any unusual lower abdominal pain
You notice vaginal bleeding
You notice leakage of fluid from the vagina

Maternal Serum Screening

Maternal Serum Screening Test is a voluntary blood test conducted between 15 and 20 weeks of pregnancy to aid in the risk assessment of Down Syndrome, a congenital disease caused by a defect in the chromosomes.

What Is The Test For?
The Maternal Serum Screening test is used to identify pregnancies in which the risk of Down Syndrome is significant enough to justify considering an amniocentesis.

How Does It Work?
Conducted between 15 to 20 weeks of pregnancy, the test measures the amount of AFP (alpha-fetoprotein) and hCG (human chorionic gonadotrophin). These substances are produced by the foetus and the placenta, and can be detected in the mother's blood.

Together with mother's age, the measurements of AFP and hCG are used to calculate her risk of carrying a baby with Down Syndrome. The test provides the mother with her individual risk of having a baby with Down Syndrome. This numerical risk is classified into either "low-risk" or "high-risk" using a cut-off risk of 1 in 250 to help mothers decide whether or not to go for an amniocentesis.

Why Measure These Substances?
We know that women with low AFP in their blood may have a higher than average risk of having a baby with Down Syndrome. It appears that babies with Dow Syndrome tend to produce less AFP than normal babies, and therefore less of it is transferred to the mother.

The level of hCG tends to be higher when Down Syndrome is present.

The reason of these differences is not known. However, a delay in maturity of Down Syndrome babies may be a cause as these two substances are associated with foetal maturity.

The measurement of these substances helps doctors to estimate more accurately a mother's risk of carrying a baby with Down Syndrome.

What Does The Test Result Mean?
In pregnancies with increased risk for Down Syndrome, the amount of AFP is lower and the amount of hCG is higher.

A "high risk" result does not mean that the baby has Down Syndrome. It only means that there is an increased risk that causes enough concern for your specialist to offer an amniocentesis (a diagnostic test for Down Syndrome) to confirm or refute the presence of a Down Syndrome pregnancy.

Likewise, a "low risk" result is not a guarantee that your baby will be healthy. If your test shows a "low risk" result, it means there is a lower chance of a Down Syndrome baby being born, so no further action is usually required.

Example
Your individual risk is quoted as 1 in 250. What this means is that out of 250 pregnancies, only one of them will be affected and 249 will be normal.

If your risk is shown to be more than 1 in 250 of having a baby affected by Down Syndrome (for example 1 in 50), you will be offered an amniocentesis to confirm or refute the presence of Down Syndrome.

Why Is The Serum Test Done Between 15 And 20 Weeks of A Pregnancy?
Experience has shown that the blood test works best between 15 and 20 weeks of pregnancy. Having the test conducted during this period allows time for intervention, if needed, before the pregnancy is more advanced. It has also been shown that the risk calculated is more accurate if an ultrasound scan has been done to confirm the age of the pregnancy and to exclude multiple pregnancies.

Can The Test Screen For Other Types Of Abnormality?
Yes. The test can also indicate if there is an increased risk for other abnormalities, particularly open spina bifida, a defect of the backbone. This is indicated by the presence of a high AFP level. When this happens, a detailed ultrasound scan will usually be arranged for further investigation.

What Happens When An Abnormality Is Discovered After Amniocentesis Or During An Ultrasound Scan?
Your specialist will provide you with detailed information about the abnormality discovered and how it may affect your baby. You may decide to terminate the pregnancy if it is a major abnormality.

If The Test Result Is "Low Risk", Does it Guarantee That The Baby Will Be Healthy?
No. The screening test is not a guarantee that the baby will be healthy. It only helps to screen for Down Syndrome and spina bifida. If the test result is "low risk", it means that the chances of having these conditions are reduced.

Overall, about 6 -7 out of 10 Down Syndrome babies will be detected by the serum screening. However, there will be still be some that are undetected and will be born to mothers who have had a "low-risk" result.

Using a cut-off risk of 1 in 250, the rate of detection among mothers at "high risk" has been shown to vary according to the maternal age as indicated below :
Maternal age Detection rate

Less than 20 years 46 %
Between 20 - 24 years 47 %
Between 25 - 29 years 50 %
Between 30 - 34 years 60 %
Between 35 - 39 years 77 %
Over 40 years 91 %

Do I Need The Test?
The test is entirely voluntary. In deciding whether or not to have the test, you should consider carefully what you and your spouse would do if the test reveals an increased risk of Down Syndrome or other abnormalities.

What Should I Do If I Would Like To Go For The Maternal Serum Screening Test?
Please inform your doctors if you wish to have the test. You will then be given an appointment for the blood test between 15 to 20 weeks of your pregnancy based on an ultrasound scan.

A Word Of Reassurance
The great majority of babies are healthy. Reading the information here may have started you worrying about some possible problems with your pregnancy. Please keep in mind that the great majority of babies are born perfectly healthy. For most women, the test is likely to provide further reassurance that all is well.

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The information is provided by KK Hospital - Singapore's leading Women and Children's Hospital. Please visit www.kkh.com.sg for more information.

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