Alpha-Fetoprotein (AFP) Tests In Pregnancy

Alpha-Fetoprotein (AFP) Tests In Pregnancy


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Modern style and rhythm of life relatively often leads to having children with development and genetic abnormalities. To prevent the birth of nonviable newborns or those whose lives will be a torture for both themselves and their loving ones, scientists are developing new methods of intrauterine diagnostic for such abnormalities.

Recently alpha-fetoprotein test (AFP) test has become quite popular. Every pregnant woman is recommended to make it in the first trimester of gestation (1-12 weeks), optimally between 10-11 weeks. The accuracy of the screening is about 90-95% if it’s performed correctly and the result is confirmed by additional research. It’s officially recognized that AFP is only the first step in diagnosing pathological pregnancy and in no case the only method.

What is Alpha-Fetoprotein

Alpha-fetoprotein (AFP) is a specific protein that is synthesized (produced) in the yolk sac or by the fully formed liver cells (hepatocytes) of the developing embryo or fetus, or by the yellow body of the woman’s ovary up to 5 weeks of pregnancy.

Alpha-fetoprotein is essential for fetal development and performs a number of specific functions:

  • it is a transport protein that transfers the necessary proteins from the mother's blood to the fetus assuring growth and development of fetal tissues and cells;
  • transfers essential fats (polyunsaturated fatty acids) involved in the formation of cell membranes, and during the last 3-4 weeks of the intrauterine life forms surfactant (ingredient, enveloping the pulmonary alveoli essential for breathing after the birth);
  • prevents the influence of maternal hormones (estrogen) on the fetus;
  • supports the blood pressure in the fetal vessels at the physiological level;
  • directly participates in the formation of natural immunosuppression between the mother and the fetus(i.e. reduces production of the woman’s immune cells on the developing child),which contributes to the normal gestation and doesn’t let the maternal body reject the fetus.

After 5 weeks of pregnancy AFP gets to the woman’s blood through the amniotic fluid where it is secreted together with the fetal urine.

Indications for Test

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All pregnant women are recommended to undergo this test before 12 weeks of pregnancy. Repeated tests are administered in case if the first test has shown any deviation.

There are several strict indications for the test:

  • a child conceived from blood relatives;
  • the birth of a previous child with developmental disabilities or a hereditary pathology;
  • the first birth after the age of 35 years;
  • negative impact on the body of a pregnant woman of various physical factors (poisons, radiation, etc.);
  • previous infertility in the parents, miscarriages (spontaneous), stillbirths;
  • intake of toxic medications shortly before pregnancy or in early pregnancy;
  • presence of a hereditary pathology or a genetic mutation in either of the future parents;
  • carrying out x-ray in early pregnancy.

How Performed the AFP Test

To get precise and informative results you should stick to the following simple rules:

  • 10-14 days before the test avoid any medications as they tend to accumulate in the blood and internal organs and can distort the fetal protein test’s results;
  • the day prior to the test abstain from greasy, sweet, salty, spicy foods and alcoholic beverages;
  • 1-2 days prior to the AFP testing limit any physical activity (including carrying of heavy loads, big cleaning of the house, etc.);
  • the last meal is no later 9 pm the day before the test;
  • in the morning on the day of test you are allowed to take only pure water, no more than 100-200ml in order not to reduce the real protein levels in the blood;
  • AFP test is taken in the morning, a few hours after waking up, so the lab must be in proximity to your house.

AFP Normal Levels Depend on the Term of Pregnancy

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At various stages of pregnancy, the concentration of alpha-fetoprotein in a woman's body is different. It is measured in international units for 1 ml of blood (IU/ml).

Elevated AFP Levels

Elevated AFP levels indicate a pathology of pregnancy. This includes many disorders, so the doctor should warn you in advance that there may be a need for additional researches such as ultrasound, HCG test (human chorionic gonadotropin), amniocentesis (amniotic fluid testing), etc.

Reasons

  • multiple pregnancy;
  • any viral infection in the mother passed on the liver tissue to the baby;
  • increased fetal body weight;
  • intrauterine growth retardation (IUGR);
  • omphalocele in the baby;
  • the anterior abdominal wall defect (gastroschisis);
  • defects of the urinary system (absence of one or both kidneys, polycystic kidneys, kidney deficiency, etc.);
  • neural tube defects(cleft spine, lack of spinal brain etc.);
  • digestive system defects (esophagus or intestine have a blindly closed end, shortening of the intestines, stomach structure violation);
  • hydrocephaly;
  • hydatiform mole;
  • chromosomal diseases (Down's and Patau Edwards syndromes);
  • diabetes or hypertension in the mother;
  • obesity 2-3 degrees in the mother;
  • severe gestosis (toxemia);
  • threat of abortion.

Effect on the Body

In the case of minor deviations from the AFP normal concentrations no measures are required. Most likely, the gestational age was defined incorrectly. However, if the test showed substantial deviations from the generally accepted norms, the woman should make ultrasound and if necessary amniocentesis to take a decision in favor of abortion.

Low AFP Levels

Insufficient concentration of AFP in the mother’s blood is less common, but it also indicates a number of abnormalities in the fetus.

Reasons

  • the threat of spontaneous miscarriage (up to 15 weeks) or preterm delivery (starting from 16 weeks);
  • hydatiform mole;
  • intrauterine growth retardation (IUGR);
  • fetal death (missed miscarriage);
  • chromosomal diseases (Down's and Patau Edwards syndromes);

Effect on the Body

In the case of decreased fetal protein concentrations confirmed by additional researches, the woman may need intensive and urgent treatment on maintenance of pregnancy and fetal development, or take the decision on the termination of pregnancy in relation to the nonviability of the fetus.

Video: AFP Screening 

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