Determination of gestational age - which method is most accurate?

Determination of gestational age - which method is most accurate?
Methods

definition of the term pregnancy Gestational age is important for physicians to watch for pregnant women. It allows you not only to set the date of birth, but also to understand whether normally developing child - for each gestational age has its own standards development. If the gestational age is unknown, doctors are extremely difficult, for example, to make a decision about whether to have an abortion patient (if he wants to terminate the pregnancy), can be used artificial induction of labor Stimulation of delivery - whether to be afraid of? If there is a threat to the life of the mother or child, and so on. Therefore, the definition of pregnancy - one of the first tasks performed by a doctor when he first examines a pregnant patient.

Since the exact date of conception set Conception - as the emerging life in most cases it is not possible to accurately determine the maximum term of pregnancy, using a variety of methods.

Ultrasonography

The basis of this diagnostic procedure is the technology of obtaining an image with ultrasonic waves. The waves pass through the skin of the abdomen, are reflected from located in the abdominal cavity structures, and a special device converts it into an image that is displayed on the monitor. During the ultrasound, doctors measure the size of the membranes fetal growth. If the survey takes place after the sixth week of pregnancy, six weeks added to the figure indicating the growth of the fetus in millimeters, and this way it is calculated gestational age. For example, if the growth of the fetus is 21 mm, its gestational age - nine weeks (6 weeks plus 21 day = 9 weeks).

When ultrasound is performed before the sixth week of gestation, gestational age is determined based on other factors such as the size of the fetus and the diameter of the membranes. The size of membranes can be measured quite accurately, since the fourth week of pregnancy.

The first day of the last menstrual period

Based on the start date of the last menstruation period of pregnancy can be determined fairly accurately (error may be plus or minus two weeks). The date of the beginning of pregnancy is generally considered the first day of menstruation as to establish exactly when conception occurred, is usually not possible. Thus, in order to establish the gestational age at the moment, the doctor counts how many days have passed since the onset of menstruation, the patient. To determine the expected delivery date to the first day of the month added 280 days.

Note that the error in the determination of pregnancy unavoidable in most cases. Precisely determine the duration of pregnancy is possible only in case if a woman became pregnant via artificial insemination (procedure in which sperm are introduced into the uterus) or in vitro fertilization.

Bimanual examination

In the course of this examination, the doctor enters the patient's vagina with two fingers, and presses on the cervix. Then the fingers of the other hand, he feels the uterus. The size, shape and firmness of the uterus allows to determine whether the patient is pregnant, and in some cases quite accurately determine the time of pregnancy.

Analysis of the level of human chorionic gonadotropin

The hormone, which is called human chorionic gonadotropin (hCG) in the blood of pregnant women. He begins to be generated in the first hours after a pregnancy occurs, and by the end of the first trimester, it increases the level of thousands of times. Assay for HCG, tend to make between the fifteenth and twentieth week of pregnancy, when carried out a thorough examination of the mother and child, during which doctors look like a developing fetus, and sometimes identified certain malformations. However, by analyzing this hormone can also set a pregnancy at the earliest timing when routine tests and other methods more useless.

During the first three weeks of pregnancy chorionic gonadotropin levels in the blood may be between 5 mIU / ml (milli-international units per milliliter) and 50 mIU / ml. Is considered to mean level of 14 mIU / ml and 42 mIU / ml. In the fourth week of human chorionic gonadotropin levels can range from 10 mIU / ml to 425 mIU / ml, and the fifth week - 19 mIU / ml to 7340 mIU / ml. The level of hCG continues to grow until about the twelfth week of pregnancy, when it reaches an average of 288,000 mIU / mL; starting from the second trimester it will gradually decline.

Due to the fact that the range of normal values of the level of human chorionic gonadotropin greatly, and rules for different stages of pregnancy may be the same (e.g., 45 mIU / mL - this is normal, and for the third and for the fourth and fifth weeks), analysis HCG - not a perfect tool to determine gestational age. Nevertheless, it can often quite successfully establish gestational age - error while rarely exceeds that which happens in the calculation of gestational age from the date of the last menstrual period. In addition, the analysis on human chorionic gonadotropin is very effective for the detection of multiple pregnancies Multiple Pregnancy - Are there any special recommendations? If a woman waits for two or more children, the level of this hormone is much higher than when she bears a child.