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Pregnancy testing
Translated by Olja Arsic - Graduated translator English, Italian and Serbocroatian
oljaarsic@hotmail.com
An important medical examination in pregnancy is laboratory testing.
Even before a woman is pregnant it is recommended to perform some tests in order to check her general health condition or to find out if there are possible preexisting pathologies such as anaemia, diabetes, any infectious disease, etc.
During pregnancy a periodic laboratory check, advised by the doctor, will provide information about the natural evolution of the pregnancy or will help in making a prompt diagnosis in the event of any pathology caused by pregnancy. Some of these pathologies can be anaemia (very frequent), gestational diabetes, urinary infections, gestosis. Their prompt diagnosis will help the doctor to decide adequate treatment preventing any further complications in that way.
It is important to remember that the physiological changes of the pregnant woman will affect the parameters of laboratory tests (for example haemoglobin, creatinine, etc.), so they will be different from standard parameters. Many laboratories use an asterisk to mark the parameters different from standard ones. For this reason many women will be concerned, thinking that these divergences mean the presence of some pathology. That is why the laboratory tests should be read only by doctor. During the periodic visit the doctor will give his opinion about the tests and will prescribe treatment, if necessary, or other tests to be performed subsequently
Pregnancy test
If your period is late it is a good idea to perform a pregnancy test in order to find out whether you are pregnant or not. In the pharmacy you can buy a sensitive pregnancy test kit that is also easy to use. Otherwise you can perform this test in one of the laboratories, leaving a specimen of urine for analysis. Pregnancy tests detect the presence of a hormone called human chorionic gonadotropin (hCG) in the first morning urine. This substance is produced very early, immediately after the conception and is constantly increasing until the third month of pregnancy. If there is any doubt or an early pregnancy pathology, such as miscarriage or extra-uterine pregnancy, it is advisable to check the presence of the HCG in the blood, because blood tests can pick up HCG earlier in a pregnancy than urine tests can.
Urine test
The complete urine test is very simple and can give us very important information. If the nitrite test is positive and there is high quantity of bacteria and leukocytes in urine, we can suspect urinary tract infection (very common in pregnancy). To confirm this hypothesis it is necessary to perform a urinoculture with antibiogram in order to find out which bacteria provoked the infection, bacterial concentration and the antibiotics they are sensitive to. If there are symptoms of cystitis, such as a burning sensation during urination (dysuria) and frequent urination (pollakiuria) a urinoculture should be performed. Very often the bacteria found in urine are introduced from the vagina or the rectum into the urinary tract. In this case we cannot talk about infection
Blood test
Blood Group and Rh Factor
If a woman has not performed this test she will have to do it at the beginning of a pregnancy. If her blood group is A, B or AB it is not necessary to know her partner's blood group. If her blood group is 0 positive, it is advisable for her partner to perform the test too. If his blood group is A, B or AB, the newborn baby may have jaundice, due to an AB0 incompatibility. Even though this disease is not acute, knowing the father's blood group could facilitate the diagnosis. The blood typing determines not only the blood group but also Rh factor (positive or negative). Blood is typed according to the ABO blood typing system and Rh factor.
Indirect Coombs Test
If a mother is Rh negative, it is necessary to know the father's blood group. If he is Rh positive, the foetus may be Rh positive too, hence incompatibility between the mother and the child may occur. The mother produces antibodies against the Rh antigen which pass through the placenta, destroying foetus' red blood cells and provoking in that way Haemolytic disease of the newborn. Fortunately, incompatibility never occurs during the first pregnancy. Today, if an Rh negative woman delivers an Rh positive baby, she receives specific immunoglobulins. This prevents immunization and incompatibility during the subsequent pregnancies. It is recommended to perform this treatment in the case of threatened miscarriage with bleeding, spontaneous or voluntary abortion, abdominal traumas, chorionic villus sampling (CVS), amniocentesis and cordocentesis. In any case, when the mother is Rh negative and the father is Rh positive, it is necessary to perform indirect Coombs test each month in order to prevent Rh incompatibility. If everything is normal, the test result should be negative. On the other hand, there are no problems if both the mother and father, are Rh negative or if the mother is Rh positive and the father Rh negative.
Complete Blood Count (CBC)
This test reveals the quantity, dimension, characteristics and type of cells that are present in blood, i.e. red blood cells, white blood cells and platelets.
The CBC's parameters obtained from pregnant women are different from those obtained from non pregnant women because of the dilution of the blood during the pregnancy. During pregnancy there is a decrease in the number of red blood cells, haemoglobin (the substance which transports oxygen), and haematocrit (the ratio of the volume of red blood cells to a given volume of blood). On the other hand, the white blood cells can slightly increase in number. Considering the variation in the blood composition during a normal pregnancy, we talk about anaemia when the haemoglobin values fall below 10 mg/dl.
The presence and type of anaemia can be revealed by performing the Complete Blood Count and observing the dimension of red blood cells. In the case of Mediterranean anaemia and iron-deficiency anaemia, the red blood cells are smaller than normal (microcytic anaemia), while in cases of folic acid deficiency anaemia or vitamin B12 deficiency anaemia, they are bigger than normal.
During the pregnancy, even if the values are normal, it is recommended to repeat the Complete Blood Count periodically, in order to discover any tendency towards anaemia or other pathologies in time.
Haemoglobin electrophoresis
This test is necessary in the case of microcytic anaemia (small volume size of red blood cells). It can also be used to determine whether there is Mediterranean anaemia known as thalassemia or any other haemoglobin-related blood disorder. In Italy, Mediterranean anaemia is present mostly in Polesine (the province of Ferrara), Sardinia and some other Mediterranean regions. If the result of mother's haemoglobin electrophoresis is abnormal, the father should perform the test as well. If his results are normal, the child will have no problems as he or she can be the immune gene carrier. On the other hand, if the father is thalassemia heterozygote, the child may be affected by the grave form of illness (Cooley's anaemia) in 25 % of cases. In that case, the parents can choose if they want to perform further examinations.
Serum iron
Serum iron test measures the amount of iron in the blood. The iron-deficiency anaemia is very common in pregnancy. The person with this type of anaemia should take iron supplements and follow an appropriate diet. It is important to say that anaemia is diagnosed if the haemoglobin values are bellow 10mg/dl. Measurement of ferritin may give more information about the amount of iron stored in the body.
Glycemia
This is the only test which requires fasting beforehand.
It measures the amount of glucose (sugar) in the blood. Even if the results are normal, it should be performed periodically during pregnancy. If the values stay close to the limit (110) for a long period of time, one should suspect reduced carbohydrate tolerance or gestational diabetes; hence it would be necessary to perform further testing to ensure a more precise diagnosis.
The One Hour GTT with a 50 gram Glucose Challenge (The O'Sullivan Screen)
In order to control the body's response to the administrated sugar, it is suggested to perform The One Hour GTT with a 50 gram Glucose Challenge (The O'Sullivan Screen) in the following cases: glycemic values above the normal ones, obesity and/or excessive weight gain, previously having large babies, presence of glucose in the urine, and family history of diabetes. Glycemia is measured before and one hour from the time you finish drinking the glucose beverage (50g dose). The normal value for blood glucose is below 140 . This test is usually performed in the period from the 20th to 24th week of gestation.
The Three Hour GTT with 100 gram Glucose Challenge
If the results of the previous test (The O'Sullivan Screen) are abnormal, it is recommended to perform the Three Hour GTT on an empty stomach, with 100 gram Glucose Challenge. Normal values must be below 110 on an empty stomach; below 190 after an hour; below 165 after 2 hours, and below 145 after 3 hours. If this test is abnormal as well, it means that there is latent diabetes which needs to be treated with a diet or insulin, in order to prevent any foetal damage. If there is a predisposition to diabetes, it would be necessary to perform this test in the preconception period. In order to have more precise diagnosis, it may be useful to measure glycolised hemoglobin and fructosamine too.
Creatininaemia
This test measures the amount of creatinine, which is the waste by-product of metabolism in the blood. The increase in creatinine levels is the sign of some kidney dysfunction. As it was previously said for the Complete Blood Count, as a consequence of the dilution of the blood during pregnancy, there will be a slight decrease in the creatinine values as well. Therefore, it is considered normal when the values are slightly inferior when compared to the non-pregnant condition. On the other hand, one should be cautious if the values of creatinine are close to the highest limits.
Transaminase AST – ALT
Transaminase AST – ALT are enzymes which are present in the liver. An elevation of the levels of these enzymes in the blood may indicate the presence of hepatic disease. In that case, it will be necessary to repeat the test in order to find the cause of the disease.
VDRL and TPHA
These are serological tests that detect syphilis infections. If the tests are positive, the doctor will prescribe an adequate antibiotic therapy during the first trimester of pregnancy.
Hepatitis B surface antigen (HBsAg)
This test indicates the presence of the hepatitis B antigen in the blood. If transaminases are normal, it means that although the woman is a healthy carrier of infection; she may infect the baby during the delivery. If the woman is HbsAg positive, in order to prevent the infection, the baby will receive specific immunoglobulins immediately after delivery. If the child is vaccinated, he/she can be breastfed. If the mother is HbsAg positive, the father and the other members of the close family must be vaccinated too. This test has to be done only one time during the pregnancy.
Anti-HCV
This test detects the presence of antibodies to the hepatitis C virus. If it is positive, the measurements of the virus genome (HCV RNA) should be done in order to check if beside the antibodies there is the presence of the virus too. If the results are positive, there is a low risk of infection for the baby.
Toxoplasma test
The toxoplasma test looks for the antibodies to a parasite called Toxoplasma in the blood.
The presence of IgG antibodies , with IgM negative, indicates that a woman is immune. The immunity against toxoplasmosis remains forever. In that case one does not need to repeat the test or follow the suggestions. On the other hand, if the test is negative, one ought to repeat it every 4-6 weeks until the end of pregnancy, because the possibility of the baby getting infected increases over time, although the gravity of disease diminishes. If seroconversion occurs in a previously negative woman, i.e. the specific antibodies of IgM type appear, an antibiotic therapy needs to be done in order to limit the possibility of the foetus getting infected.
Rubella test
The rubella test detects the presence of rubella antibodies in the blood.
If the antibodies are not present in the body and the test is negative, it should be repeated every 4-6 weeks, until the end of the fifth month. After that period, the virus can no more cause any damage to the foetus. If seroconversion occurs in a previously negative woman, i.e. the specific antibodies of IgM type appear, other tests need to be performed in order to limit the possibility of the foetus getting infected.
Cytomegalovirus Antibody test
It detects the presence of antibodies against the cytomegalovirus in the blood.
The presence of specific IgG type antibodies with the absence of IgM antibodies indicates a state of immunity, while the absence of both antibodies indicates that the contact with the virus never occurred. If, at the beginning of pregnancy, a woman has IgG positive and IgM negative, the test is not repeated, but if she is not immune (if she does not have enough antibodies) she will have to repeat it every 4-6 weeks. Unlike rubella and toxoplasmosis, the immunity against cytomegalovirus is not permanent, hence the possibility of reinfection exists in 1% of women. Many doctors consider it unnecessary to perform this test, because there is no specific treatment or vaccine that can prevent infection of the foetus. If seroconversion occurs during the pregnancy, in a previously negative woman, i.e. specific IgM type antibodies appear, it will be necessary to perform other tests in order to eliminate the possibility of the foetus becoming infected.
Tests for Herpes 1 and 2
The measurement of antibodies against herpes simplex 1 (oral herpes) and herpes simplex 2 (genital herpes) is no longer a routine pregnancy test. If a woman is at risk, it is preferable to perform a colposcopy at the end of the pregnancy, because during vaginal delivery, there is a high risk of mother-to-child virus transmission. If at the time of birth there are visible genital herpes lesions, in order to prevent infection of the infant, caesarean section is medically indicated.
Human Immunodeficiency Virus (HIV)
This test detects the presence in the blood of antibodies against the AIDS virus. It is routinely performed in pregnancy, because mother to child transmission is greatly reduced by following proper pharmacological prophylaxis, performing caesarean section and avoiding breastfeeding (not more than 5% against 15-20% without these precautions). It is performed only at the beginning of pregnancy.
Pap-smear
Most women have already had this test before they become pregnant. The test is easy to perform and does not involve any risk for the baby. It should be carried out only if the last test was performed more than 2 years previously. In fact, the screening for cervical cancer is effective only if carried out at not more than two-year intervals.
Vaginal swab
Vaginal and rectal swabs are usually taken in the period from the 35th to 37th week of gestation, in order to determine the presence of the beta-haemolytic group B Streptococcus (GBS). This microbe, if present in the vagina or rectum during labour, may cause infections of the baby which in rare cases can be very serious. If the bacteria found to be present (the mother usually has no symptoms) she receives antibiotic prophylaxis during labour. If necessary the baby may receive the treatment too. The prophylaxis is still more important in the conditions of grate risk, for example preterm birth, preterm rupture of amniotic sac membranes or high fever during labour. Of course, if suspicion of vaginal infection exists, the vaginal swab may be performed to detect other types of bacteria at any time during pregnancy.
25 Luglio 2005