TESTS PERFORMED DURING PREGNANCY

Determining the Rate of Abdominal Growth in Pregnancy

At the beginning of the second half of pregnancy, the uterus reaches the level of the umbilicus and can be felt by hand. Afterwards, in measurements performed while the bladder is empty, the distance in centimeters measured with a tape between the pubic bone and the highest point of the uterus gives the gestational week with a small margin of error. Factors such as twin pregnancy, excessive obesity, an overly full bladder, and lack of experience of the person performing the measurement may contribute to misleading results of this test.
This assessment is gradually being abandoned today because most doctors perform an ultrasound at every antenatal evaluation.
 
Determination of Blood Groups

The blood groups of the expectant mother and father can be determined from a finger-prick blood sample. If the mother’s blood group is Rh(-) and the father’s blood group is Rh(+), this is called Rh incompatibility.
 
Complete Blood Count (Hemogram)

Many different blood parameters are determined automatically by devices that count cells in blood taken from a vein. In addition to leukocyte (white blood cell) count, erythrocyte (red blood cell) count, average hemoglobin content of erythrocytes, their size, platelet count, hemoglobin and hematocrit values, many more parameters are determined. A diagnosis of anemia is made and a general idea is obtained as to whether this is due to iron deficiency, vitamin B12 and/or folic acid deficiency, or a hereditary disease (such as thalassemia carrier status).
When the leukocyte count rises above the physiological increase associated with pregnancy (12,000 and above), this may indicate infection; when it is excessively low, it may point to a disease that impairs white blood cell production. If the platelet count is found to be lower than the physiological decrease expected in pregnancy, a disease that causes unnecessary consumption of these cells, which are responsible for stopping bleeding, is suspected.
 
Complete Urinalysis (CUA)

Urine is a mirror of the body. By examining the urine sediment, urinary tract infection and the presence of stones or “sand” in the urine can be detected and appropriate treatment can be initiated. The presence of protein (albumin), acetone (ketone), bilirubin, blood cells, and excessive increase in urobilinogen in the urine is always abnormal and requires further investigation. The presence of glucose in the urine is considered normal to a certain extent in pregnancy, but still requires further evaluation.
CUA is performed quite frequently during pregnancy. The aim is to detect signs of infection in the urine, to evaluate the general nutritional status of an expectant mother who has excessive nausea and vomiting in early pregnancy (the presence of acetone (ketone) in the urine indicates starvation, and ketone positivity increases in direct proportion to the degree of starvation), to detect the presence of protein in the urine in later stages of pregnancy (protein in the urine may be a sign of preeclampsia), and to assess whether the expectant mother is drinking enough water (when fluid intake is inadequate, the color of the urine darkens and its density (specific gravity) increases).
 
Urine Culture

Pregnancy facilitates the development of urinary tract infections. The presence of leukocytes, erythrocytes and/or bacteria in the urine sediment indicates infection and requires antibiotic treatment if the expectant mother has symptoms. However, since antibiotics do not act against all types of bacteria, it is more appropriate to determine the type of bacteria by urine culture and treat the infection accordingly. In a urine sample taken under appropriate conditions, the bacteria present are grown by adding special nutrients, and the sensitivity of the bacteria to certain antibiotics is measured. If there is no growth in culture, the urine is called “sterile”, meaning that it does not contain bacteria requiring treatment. If growth is “below 100,000 colonies”, it is suspected that the bacteria grown do not originate from an infection in the expectant mother herself but from contamination from the container, genital tissues or other sources, and the test is repeated if necessary. If there is “growth above 100,000”, this definitely means that there are enough bacteria in the urinary tract to require treatment. Appropriate antibiotic therapy is given according to the antibiogram report, which indicates which antibiotics the bacteria are sensitive to, and 15 days after the end of treatment, the urine culture is repeated to evaluate treatment success.
Even if the expectant mother has no complaints, if growth is detected in the urine culture, antibiotic treatment is given to prevent serious infections that may develop later. For this purpose, a urine culture is performed once at the beginning of pregnancy and, if possible, once more towards the end in expectant mothers, to detect any possible growth and treat it appropriately.
 
Infection Screening Tests

Toxoplasma, Rubella (German measles) and Syphilis screening tests are preferably performed when pregnancy is being planned. For this purpose, Toxoplasma IgG and IgM (antibodies), Rubella IgG and IgM, and usually a test called VDRL for syphilis are performed on blood taken from the expectant mother. These three infections are among the leading infections that can cause anomalies in the baby when contracted in early pregnancy, and therefore it is more appropriate to identify them before pregnancy.
Screening tests for Hepatitis B and HIV (AIDS) are usually performed towards the end of pregnancy. For Hepatitis B screening, HBsAg and Anti-HBs tests are performed. If carrier status is detected in the expectant mother, in order to prevent the baby from acquiring the infection from the mother, the baby must receive immune serum treatment shortly after birth in addition to vaccination.
 
Ultrasound (vaginal, abdominal)

The ultrasound performed at the first antenatal examination and preferably in the first weeks of pregnancy is very important. This ultrasound is crucial to confirm the accuracy of the Last Menstrual Period (LMP); to determine the gestational week in expectant mothers who do not know their LMP; to detect conditions such as ectopic pregnancy and molar pregnancy at an early stage; to identify mass lesions such as myoma or ovarian cyst that may have a negative impact on pregnancy; and to detect a possible multiple pregnancy. For this purpose, in early pregnancy weeks (up to the 14th week), vaginal ultrasound is preferred, but abdominal (transabdominal) ultrasound can also be used.
In later weeks of pregnancy, some doctors prefer to perform an ultrasound examination at every antenatal visit. Although this is not absolutely necessary, it is important to perform a detailed ultrasound examination once between the 19th and 23rd weeks of pregnancy for anomaly screening following the first ultrasound.
In addition to routine ultrasound examinations, ultrasound is repeated in any situation where there is doubt about whether the baby is alive (such as threatened miscarriage, not feeling fetal movements, cessation of abdominal growth); when there is suspicion of IUGR (intrauterine growth restriction); in the evaluation of post-term pregnancy; and in any situation where the course of pregnancy deviates from normal (such as febrile infection, elevated blood pressure, pain).
 
 

IDC (Indirect Coombs Test)

If the mother’s blood group is Rh(-) and the father’s blood group is Rh(+), this is called Rh/Rh incompatibility. It is an investigation requested in expectant mothers with blood group incompatibility. At certain intervals, antibodies that may develop against the baby’s red blood cells are determined in the blood by this method. If antibodies are found to be positive, further investigation may be required.
 
Triple Test (Second Trimester Down Syndrome Screening Test)

This is an investigation performed between the 16th and 18th weeks of pregnancy. By testing three different hormones in the blood taken from the expectant mother, the risk of Down syndrome and neural tube defect is determined. Today, the quadruple test, which is a more advanced version, is used more frequently.
 
Triple Test

The triple test is a blood test recommended for all expectant mothers between the 16th and 18th weeks of pregnancy. Three different hormone measurements are performed in the blood taken from the expectant mother. The hormone measurement results, together with variables such as the expectant mother’s age, weight, smoking status, and gestational week, are entered into a special computer program and processed. As a result of this process, the probability that the baby has Trisomy 21 (Down syndrome), Trisomy 18 and neural tube defect (NTD) is determined. In the triple test report, the risk for each of these three abnormal conditions is stated separately.

The hormones measured in the blood taken from the expectant mother at the appropriate gestational week are the hCG (human chorionic gonadotropin) hormone, which you are familiar with from the pregnancy test section, AFP (alpha-fetoprotein), most of which is secreted from the baby’s liver and passes into the mother’s blood, and a hormone called uE3 (unconjugated estriol). The levels of these hormones in the mother’s blood show significant changes according to gestational weeks.

During the development of the triple test, measurements of these three hormones were made in blood samples taken from a large number of expectant mothers whose gestational weeks were known precisely, and normal values were determined as lower and upper limits. For convenience and to standardize units, these normal values are expressed as MoM (multiple of median). In the mothers from whom these measurements were taken and who later delivered babies with Down syndrome, Trisomy 18 and NTD, the degree of deviation from the MoM value was calculated, and the extent to which this deviation increased the risk was determined statistically. The risk assessment system was then automated with the help of a computer program.

In summary, the MoM values determined in the blood sample, together with variables such as age, weight and gestational week, are entered into a computer program, which compares them with the data in its database and provides a numerical risk according to the degree of deviation from normal.

 
Quadruple Screening Test

The quadruple screening test (quadruple test) is a blood test recommended for expectant mothers between the 16th and 21st weeks of pregnancy. Four different hormone measurements are performed in the blood taken from the expectant mother. In fact, the quadruple test is a test created by adding a substance called Inhibin A to the three parameters measured in the triple test in order to increase screening sensitivity.

In this test, as in the triple test, the results of the four hormone measurements, together with variables such as the expectant mother’s age, weight, smoking status, and gestational week, are entered into a special computer program and processed. As a result of this process, the probability that the baby has Trisomy 21 (Down syndrome), Trisomy 18 and neural tube defect (NTD, spinal opening in the baby) is determined. In the quadruple test report, the risk for these abnormal conditions is stated separately.

The sensitivity of the triple test is accepted as 60%.

When the substance called Inhibin A is added to the measurements, in other words when the quadruple screening is applied, the sensitivity increases significantly and rises to around 80%.

In the quadruple test, the substances measured in the mother’s blood are beta-hCG, alpha-fetoprotein (AFP), unconjugated estriol (uE3) and Inhibin A. These values are compared with the average for an expectant mother at that gestational week to determine whether there is a deviation from normal, and if so, the degree of deviation. According to the degree of deviation, a risk, that is, a probability, is calculated.

Worldwide and in our country, since the quadruple test is more sensitive than the triple screening test, the triple test is gradually becoming obsolete.

Some doctors perform both the 11–14 test (double test) and the quadruple test together for expectant mothers, while some perform only the double test and others only the quadruple test. Each doctor acts according to the school in which they were trained and their own experience, and it is not clear which approach is superior.

When the risk is high in the quadruple test, this does not mean that there is definitely a problem in the baby; it means that the statistical probability of having a baby with a chromosomal abnormality has increased, and as in the triple test, amniocentesis is recommended.

 
11–14 Test (Double Test, First Trimester Down Syndrome Screening Test)

As the name suggests, this is an investigation performed between the 11th and 14th weeks of pregnancy. The nuchal translucency thickness of the baby is measured by ultrasound, and two different substances are measured in the blood taken from the expectant mother to determine the risk of Down syndrome. In addition to determining the risk of Down syndrome, it has other important advantages.
 

Double Test in Pregnancy – Nuchal Translucency Measurement

In Turkey, the most commonly used test for determining the risk of Trisomy 21 (Down syndrome) is still the triple test. However, the risk of Down syndrome can also be determined by measuring the nuchal translucency thickness of the baby between the 11th and 14th weeks of pregnancy, together with measuring beta-hCG and PAPP-A in the blood taken from the expectant mother, and entering these values into a computer and processing them with a special program.

Nuchal translucency thickness

With the observation that in some fetuses with various chromosomal abnormalities, especially Trisomy 21 and Trisomy 18, nuchal thickness increases due to fluid accumulation in this region, theories have been developed about the applicability of this measurement in prenatal diagnosis.

Increased nuchal translucency thickness in early pregnancy and ultrasound image of the same baby

The nuchal translucency thickness of the fetus may increase due to many reasons other than trisomy. Among these, a fluid accumulation called cystic hygroma is a condition that has long been known to be associated with Turner syndrome (a chromosomal abnormality of 45 XO). Indeed, in babies diagnosed with cystic hygroma and therefore undergoing further investigation, a chromosomal abnormality called Turner syndrome is found in 70% of cases.

Nuchal thickness may also be increased due to fetal heart diseases, lung diseases, skeletal disorders, congenital infections and other diseases.

Beta-hCG and PAPP-A

The level of beta-hCG in the blood decreases as pregnancy progresses. In trisomic babies, this decrease is much slower. Measurements between the 11th and 14th weeks of pregnancy confirm that this decrease is slower in babies with Trisomy 21.

PAPP-A is a substance that increases as pregnancy progresses. Again, in trisomic babies, this increase has been observed to be slower than normal.

As the name suggests, this is an investigation performed between the 11th and 14th weeks of pregnancy. The nuchal translucency thickness of the baby is measured by ultrasound, and two different substances are measured in the blood taken from the expectant mother to determine the risk of Down syndrome. In addition to determining the risk of Down syndrome, it has other important advantages.
 
PPG (Postprandial Glucose) and OGTT (Oral Glucose Tolerance Test)

Pregnancy is a condition that increases the risk of developing diabetes. For this reason, expectant mothers undergo a glucose loading test between the 24th and 28th weeks of pregnancy. For this purpose, depending on the risk factors of the expectant mother, loading is performed with 50 grams (PPG) or 100 grams of glucose (OGTT).
 
TSH (Thyroid Hormone) Measurement

A significant proportion of women of reproductive age have problems with thyroid hormone secretion. This problem, which is usually encountered as underactivity of the thyroid gland, can also occur as excessive secretion of thyroid hormones. Based on this fact, TSH measurement, which is a thyroid hormone test, is routinely performed in expectant mothers today. Normal TSH values during pregnancy are considered differently from normal adult values, and hormone supplementation is given to the expectant mother when necessary. In expectant mothers already known to have thyroid disease, additional measurements of other thyroid hormones and substances such as anti-thyroglobulin may be requested.
 
Blood Biochemistry

From the moment pregnancy begins, significant changes occur in blood biochemistry. Accordingly, the normal values of blood biochemistry parameters change, and interpretation may become difficult and even incorrect interpretations may be made.
During pregnancy, especially in the early stages, many blood tests are requested to evaluate the functions of organs, particularly the liver and kidneys. Whether it is necessary to request these tests from an expectant mother who has no specific disease is still a matter of debate.
 

Doppler Ultrasonography

Doppler Examination as a Screening Test

Studies have shown that by examining the structures that carry blood from the uterus to the placenta and from there to the baby between the 20th and 24th weeks, it is possible to identify expectant mothers at higher risk for abnormal conditions such as preeclampsia and intrauterine growth restriction in later weeks of pregnancy.

In the screening test recommended based on these data, from the 20th week onwards, the blood flow in both main uterine arteries (“uterine arteries”) is measured with a Doppler device, and the blood flow waveforms that appear on the ultrasound screen are visually evaluated.

If, as a result of the examination, notching is visually detected in the waveforms of one or both arteries and/or increased resistance is detected in the flow measurements of one or both arteries, the examination is interpreted as “pathological”. Again, a marked difference between the flow measurements of the two arteries is also considered pathological.

Unilateral notching can especially be detected in measurements performed early (at the 20th week), and this may disappear in examinations repeated at 24–26 weeks. Sometimes unilateral notching may persist until the end of pregnancy. It is difficult to comment on how much unilateral notching increases the above-mentioned risks.

It has been observed that the risk increases significantly, especially when bilateral notching is observed and this persists in repeated measurements.

Again, when increased resistance or a marked difference between the two arteries is detected, the risk of preeclampsia and/or intrauterine growth restriction is increased.

In all of the above situations, the course of pregnancy is monitored more closely.