First trimester screening is a prenatal test that offers early information about a baby’s risk of certain chromosomal conditions — Down syndrome (trisomy 21) and extra sequences of chromosome 18 (trisomy 18).Typically, first trimester screening is done between weeks 11 and 14 of pregnancy — although a form of the screening can be done as early as nine weeks.
WHAT ARE THE FIRST TRIMESTER PREGNANCY TESTS?
Ultrasound test for fetal nuchal translucency (NT). Nuchal translucency screening uses an ultrasound test to examine the area at the back of the fetal neck for increased fluid or thickening.
Two maternal serum (blood) tests. The blood tests measure two substances found in the blood of all pregnant women:
- Pregnancy-associated plasma protein screening (PAPP-A) a protein produced by the placenta in early pregnancy. Abnormal levels are associated with an increased risk for chromosome abnormality.
- Human chorionic gonadotropin (hCG) a hormone produced by the placenta in early pregnancy. Abnormal levels are associated with an increased risk for chromosome abnormality.
WHAT IS AN ULTRASOUND?
In the first trimester
- To establish the dates of a pregnancy
- To determine the number of fetuses and identify placental structures
- To diagnose an ectopic pregnancy or miscarriage
- To examine the uterus and other pelvic anatomy
- In some cases to detect fetal abnormalities
Mid-trimester (sometimes called the 18 to 20 week scan)
- To confirm pregnancy dates
- To determine the number of fetuses and examine the placental structures
- To assist in prenatal tests, such as an amniocentesis
- To examine the fetal anatomy for presence of abnormalities
- To check the amount of amniotic fluid
- To examine blood flow patterns
- To observe fetal behavior and activity
- To examine the placenta
- To measure the length of the cervix
- To monitor fetal growth
- To monitor fetal growth
- To check the amount of amniotic fluid
- As part of the biophysical profile
- To determine the position of a fetus
- To assess the placenta
HOW IS AN ULTRASOUND PERFORMED?
For the ultrasound exam, you’ll lie on your back on an exam table. Your health care provider or an ultrasound technician will place a slender, wand-like device in your vagina to send out sound waves and gather the reflections. The reflected sound waves will be digitally converted into images on a monitor. Your health care provider or technician will use these images to measure the size of the clear space in the tissue at the back of your baby’s neck. The ultrasound might take up to an hour. It doesn’t hurt, and you can return to your usual activities immediately.Test results are typically available in less than a week.
Although the specific details of each procedure vary slightly, generally, ultrasounds follow this process. Two types of ultrasounds can be performed during pregnancy:
- Abdominal ultrasound
In an abdominal ultrasound, gel is applied to the abdomen and the ultrasound transducer glides over the gel on the abdomen to create the image.
- Transvaginal ultrasound
In a transvaginal ultrasound, a smaller ultrasound transducer is inserted into the vagina and rests against the back of the vagina to create an image. A transvaginal ultrasound produces a sharper image and is often used in early pregnancy.
There are several types of ultrasound imaging techniques. The most common is two dimensional, or 2D. This gives a flat picture of one aspect of the image.
If more information is needed, a 3D ultrasound examination can be performed. This technique, which provides a three-dimensional picture, requires a special machine and special training. But the 3D image allows the health care provider to see width, height, and depth of images, which can be helpful in diagnosis. The 3D images can also be captured and saved for later review.
The latest technology is 4D ultrasound, which allows the health care provider to visualize the unborn baby moving in real-time. With 4D imaging, a three-dimensional image is continuously updated, providing a “live action” view. These images often have a golden color, which helps show shadows and highlights.
Ultrasound images may be captured in still photographs or on video to document findings.
7 ULTRASOUND SPECIALISTS IN DELHI?
The Ultrasound Lab C – 584, Defence Colony, New Delhi
Contact: 011 2433 6450
C-27, Green Park Extn, Green Park, New Delhi
Contact: +91 9958228418
DR RAHUL GERA
B7/41 Safdarjung Enclave, New DelhI
Contact: +91 9136233059
DR ANAND ASHOK VERMA
C-1/1370, Ground Floor, Vasant Kunj, New Delhi
Contact: +91 9811580166
DR SUNEET JOLLY
E-343 C Ground Floor, Greater Kailsah Part- 1, Near Gurudwara, New Delhi
Contact: 011 4651 1977
DR CHARU KOHLI
E-28, Jangpura Extension, New Delhi | C 234, Defence Colony, New Delhi
Contact: +91 9310017585
DR VANDANA CHADHA
E60-62, Hans Raj Gupta Marg, Block E, Greater Kailash I, New Delhi
Contact: +91 9310017585
WHAT ARE THE RISKS & BENEFITS OF AN ULTRASOUND?
Transvaginal ultrasound requires covering the ultrasound transducer in a plastic/latex sheath, which may cause a reaction in patients with a latex allergy.
Fetal ultrasound is sometimes offered in nonmedical settings to provide keepsake images or videos for parents. While the ultrasound procedure itself is considered safe, it is possible that untrained personnel may give parents false assurances about their baby’s well-being, or perhaps an abnormality may be missed. Having ultrasound performed by trained medical personnel who can correctly interpret findings is recommended. Talk with your doctor or midwife if you have questions.
WHAT IS A TRIPLE MARKER TEST?
The exam measures the levels of three important substances in the placenta:
Alpha-fetoprotein screening (AFP). This blood test measures the level of alpha-fetoprotein in the mothers’ blood during pregnancy. AFP is a protein normally produced by the fetal liver and is present in the fluid surrounding the fetus (amniotic fluid), and crosses the placenta into the mother’s blood. The AFP blood test is also called MSAFP (maternal serum AFP).Abnormal levels of AFP may signal the following:
- Open neural tube defects (ONTD), such as spina bifida
- Down syndrome
- Other chromosomal abnormalities
- Defects in the abdominal wall of the fetus
- Twins–more than one fetus is making the protein
- A miscalculated due date, as the levels vary throughout pregnancy
hCG: This is human chorionic gonadotropin hormone (a hormone produced by the placenta)
Estriol: This is a hormone produced by the placenta
Inhibin: This is a hormone produced by the placenta
Multiple marker screening is not diagnostic. This means it is not 100 percent accurate, and is only a screening test to determine who in the population should be offered additional testing for their pregnancy. There can be false-positive results,indicating a problem when the fetus is actually healthy or false negative results,indicating a normal result when the fetus actually does have a health problem.
WHY IS THE (hCG) TEST PERFORMED?
Pregnancy tests measure human chorionic gonadotropin (hCG), a hormone that is produced by the placenta when a woman is pregnant. The amount of hCG produced during pregnancy increases steadily during the first trimester (8-10 weeks) of a normal pregnancy, peaking around the 10th week after the last menstrual cycle.
There are two types of hCG tests: qualitative and quantitative.
Qualitative tests can be done on either urine or blood; they are usually done after a missed menstrual period to confirm that the woman is indeed pregnant.
Quantitative tests measure the actual level of hCG and are performed on blood samples. Some laboratories may have targets for what the hCG level should be for each week of gestation during the first trimester, but each woman’s levels may vary (and the exact gestational age may be uncertain). The most important feature of hCG during the first trimester is that the levels should essentially double every two or three days. If there is any concern about the pregnancy, the patient’s healthcare practitioner will often measure quantitative hCG levels several times to make sure that they are increasing at an appropriate rate.
If hCG levels are not rising normally, the cause may be an ectopic pregnancy (in which the pregnancy is occurring within the tube that leads from the ovary to the uterus or, more rarely, in the abdominal cavity) or an abnormal intra-uterine pregnancy. Ectopic pregnancy may become a medical emergency, so practitioners may need to perform vaginal ultrasound in patients whose hCG is not rising appropriately to make sure that there is a gestational sac within the uterus.
OTHER COMMON TESTS PERFORMED DURING THE FIRST TRIMESTER
BLOOD TYPING AND RBC ANTIBODY SCREEN
Blood typing is especially important during pregnancy because a mother and her fetus could be incompatible. For example, if the mother is Rh-negative but the father is Rh-positive, the fetus may inherit the Rh antigen from the father and be Rh positive. If the blood types of mother and baby are different, as in this example, the mother may produce antibodies (antiglobulins) that react with antigens (proteins or factors) on the fetus’ red blood cells. The antibodies may cross the placenta and cause destruction of the baby’s red blood cells, resulting in a serious condition referred to as hemolytic disease of the newborn (HDN). Although the first Rh-positive baby is unlikely to become ill, the antibodies produced during that first pregnancy may affect subsequent Rh-positive babies.
To greatly reduce the likelihood that an Rh-negative mother will develop this antibody, she may be treated with an injection of Rh immune globulin at approximately 28 weeks’ of pregnancy. The Rh immune globulin binds to and “masks” the fetus’s Rh antigen and prevents the mother from developing antibodies against the Rh antigen. Additional injections may be necessary during the pregnancy if she has an amniocentesis, chorionic villus sampling, or an abdominal injury, and after delivery if the baby is Rh-positive. Before each injection is given, an antibody screen is performed to make sure that the woman has not already developed Rh antibodies.
In addition to Rh-negative women who have had an Rh-positive baby, any woman who has had a blood transfusion or had prior pregnancies may produce an antibody to blood factors other than Rh that can potentially harm an unborn baby. An antibody screen done during the first trimester and repeated during the third trimester (between 28 and 29 weeks of pregnancy) determines if potentially harmful antibodies are present in the mother’s blood. If a harmful antibody is detected, the baby’s father should be tested, if possible, to see if his RBCs have antigens that the mother’s antibody could target. If so, then the fetus’ RBCs may also have antigens that may be targeted. In this case, the healthcare practitioner will likely monitor the mother’s antibody level and the health of the fetus for the duration of the pregnancy. Signs that the fetus is becoming ill may necessitate treatment before birth (such as an intrauterine transfusion) or an early delivery.
Although Rh incompatibility has more severe consequences, one of the most common causes of HDN is actually an incompatibility between the mother’s and baby’s ABO blood groups, not the Rh factor. However, the RBC antibody screen cannot be used to predict whether HDN will occur because antibodies to the ABO blood groups are naturally-occurring.
PAP TEST AND HPV TESTING
- Screening with Pap tests should begin no earlier than age 21.
- Women between the ages of 21 and 30 should have a Pap test every 3 years.
- Women between the ages of 30 and 65 should have both a Pap test and an HPV test every 5 years (preferable); a Pap test alone every 3 years is also acceptable.
- In most cases, if a woman has a negative HPV test and/or normal Pap test within the recommended interval, she will not require the tests when she becomes pregnant. If it has been more than the recommended time interval since the last cervical cancer screen, or if there are any questions about the status of the cervix, the healthcare practitioner may suggest screening pre-conception or at the beginning of the pregnancy.
Early detection of high-risk types of HPV, abnormal cervical cells, and infections and early treatment, if necessary, offer the best chance to prevent any problems from progressing and potentially affecting the health of the baby and the success of the pregnancy.
URINE SCREEN FOR GLUCOSE AND/OR PROTEIN
A high level of protein in the urine is a warning sign. It may indicate kidney damage or disease or it may be a transient elevation due to, for example, an infection, medication, or emotional or physical stress. Examples of additional tests that may be done to help determine the cause include a 24-hour urine protein test, full urinalysis, or urine culture (to identify any bacteria or yeast present; see Bacteriuria).
Of particular concern during the second and third trimesters is pre-eclampsia (sometimes called toxemia or pregnancy-induced hypertension), a disorder characterized by high blood pressure and large amounts of protein in the urine that occurs in approximately 8% of all pregnancies. Symptoms include swelling, sudden weight gain, headache, and vision changes. Risk factors include first pregnancy, being pregnant with more than one child, age (teenagers and women over 40 years of age), being African American, and having pre-existing diabetes, hypertension, or kidney disease. It can result in a decrease of air and nutrition getting to the baby through the placenta, causing low birth weight or other complications. If caught early enough, however, through routine checking of blood pressure and urine protein levels, health problems for the mother and baby due to pre-eclampsia can be managed.
High urine glucose levels may be a sign of undiagnosed diabetes that is already present in the mother or gestational diabetes, a form of diabetes that can develop during pregnancy. A positive urine test for glucose will usually be followed by a confirmatory blood glucose test, which is also routinely used to screen for gestational diabetes during the second trimester (between 24 and 28 weeks of pregnancy).
THYROID STIMULATING HORMONE (TSH)
Women with known thyroid conditions will usually require careful monitoring if they become pregnant. A healthcare practitioner may use tests for thyroid stimulating hormone (TSH) to monitor a woman’s thyroid function throughout her pregnancy. TSH is produced by the pituitary, a small gland in the brain, in response to low T4 or T3 levels. Increased TSH levels in women who are taking thyroid hormone replacement may mean that their dose of hormone replacement needs to be increased.
Some have advocated screening pregnant women during the first trimester (or even before pregnancy) for elevated TSH even if they do not have a history of thyroid disease. This is because a significant percentage of women may have an underlying thyroid disorder that is unsuspected and that will cause problems during pregnancy. However, most guidelines do not recommend this as being necessary.
COMPLETE BLOOD COUNT (CBC)
Red blood cells contain hemoglobin, a protein that gives blood its red color. It binds to oxygen in your lungs, transports it throughout the body, and releases it to the cells and tissues. During pregnancy, a woman’s hemoglobin must transport enough oxygen to meet both her and her fetus’ needs. If a woman has insufficient RBCs and/or hemoglobin, she is said to be anemic.
Many pregnant women will experience some degree of anemia. While mild anemia can make you feel tired and weak, more severe anemia in a pregnant woman can cause a fetus to receive too little oxygen to support normal development.
All women lose a small amount of blood during delivery. Although this is usually not a problem, even a small amount of blood loss can be harmful to women with anemia. A healthcare practitioner may want to know the level of hemoglobin in a pregnant woman’s blood before delivery to assess the possible impact of the expected blood loss.
White blood cells help protect the body from infections and also have other immune functions. Evaluating WBCs during a woman’s pregnancy can help detect infections so that they may be treated and resolved before they cause significant health problems in the mother or her baby.
Platelets are special cell fragments in the blood that help form clots to stop bleeding. Women with low platelet counts, or who have platelets that don’t function properly to form clots, are at risk of life-threatening bleeding during delivery. Follow-up testing may be needed to help determine treatment options if a platelet problem is detected.
CHRONIC VILLUS SAMPLING (CVS)
Any of the following are the usual indications for this diagnostic procedure:
- An earlier screening test gives a reason for concern
- The pregnant woman is 35 years of age or older
- There is a strong family history of a specific genetic disorder (in either biological parent)
- Both biological parents possess a gene for an inherited disorder
- A previous child of one of the biological parents had a birth defect
- Carefully chosen screening tests may help the woman avoid this diagnostic procedure, which is associated with a risk of miscarriage and infection.