Can the ultrasound be wrong with a pregnancy?


The availability of ultrasound diagnosis allows a woman who has just learned of pregnancy not to build guesses relative term, and to know exactly how her baby develops. Of course, when you visit the office ultrasound, the woman imply about what kind of life would call a doctor, but it happens that her expectations are not met.

How often this happens than to explain the situation, when the term ultrasound is different from a period at the monthly, or the size of the fruit differ from the standard at a specific time?

During manual examination of the pregnant, the obstetrician-gynecologist may notice that the uterus is friable and slightly enlarged. But this phenomenon is observed before menstruation. To accurately clarify the situation, need ultrasound.

Ultrasound can accurately determine pregnancy when levels of HCG (human chorionic gonadotropin) in a woman’s blood will exceed a thousand units. In this case, the doctor is able to see in the uterus the fertilized egg (multiple pregnancy – two or three ovum). The longer, the more complete picture of the study – the doctor finds the presence of not only the ovum but yolk SAC in it, or even see the embryo and heartbeat, and will be able to measure the CTE of the embryo (the distance from the coccyx to the top).

If your menstrual cycle is more than 30 days, the period of pregnancy on ultrasound and menstruation may differ significantly.

There is often such a situation: a woman comes to the ultrasound, the doctor asked the date of the last menstruation, is conducting a study, and then declaring that the pregnancy is likely to turned out to be exactly frozen – embryo and its heartbeat is not visualized, seen the fertilized egg, the size of which is smaller than it should be. The doctor may be wrong if the woman had late ovulation. A significant portion of women’s menstrual cycle is the standard 28 days, and 33, or even 35-40. This means that conception did not take place on 14-16 day cycle and a week or two later, and the woman just came on the ultrasound too early, so the fetus was not seen. Most likely the pregnancy would not be stilled and the fetus develops normally, just study it is worth repeating in a couple of weeks, so you’ll never be wrong. You can also explain the situation when for an ultrasound and did not see the pregnancy: the level of HCG in blood is less than that at which it is possible to see a pregnancy.

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The differences of pregnancy by month and by ultrasound

All obstetricians in establishing pregnancy using the term «maternity period». This allows all of the gynecologists of the world to speak the same language. It is in weeks, the countdown begins from the first day of your last period. The first and second obstetric weeks are those weeks during which the body is just maturing the egg, which is subsequently released from the ovary during ovulation to meet the sperm.

Thus, a woman who has a standard menstrual cycle is 28 days and came to the doctor with a delay of one week will have a pregnancy in obstetric exactly five weeks. At the same time ultrasound can be set a little smaller — three, four weeks. As it is justified and why the period is not the same? This situation is normal, because ultrasound aims to determine the exact time in weeks, to determine how many weeks from conception on the parameters developed fetus (his gestational age). To understand the difference between these two concepts is important. Therefore, the discrepancy between 1-2 weeks for a period by month and by ultrasound in favor of the period (i.e. the period for month more, and by ultrasound less) – a normal phenomenon, there is nothing to worry about.

How to install the pregnancy with an irregular cycle?

Some women suffer from hormonal imbalance and as a result, irregular cycle. With such pathologies as polycystic, multifollicular ovaries, excessive amounts of male sex hormones menstruation may not come for several months. However, ovulation when such violations from time to time still occur, and thus, the chances of pregnancy in such women almost as much as the others.

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If pregnancy is not desirable for you, the use of contraceptives mandatory, even if you are suffering from irregular cycle month and absent for several months.

Often women with irregular cycles do not consider it necessary to protect themselves, believing that to conceive them just will not succeed. In this case, you can detect pregnancy at the third or fourth month, because the absence of menstruation for several months becomes a kind of norm. Correct calculation of the obstetric period, in such a situation is almost impossible, so the determination of the term, the doctor may rely solely on the data of ultrasonic examination. If the fetus is not too large or too small, ultrasound can establish the gestational age of the fetus with an accuracy of up to 2-3 weeks. Date of birth will also be installed in non-traditional way – counting 40 weeks from the first day of your last period, and based on the ultrasound.

In any case, the period ahead by ultrasound obstetric?

Currently in Russia, all pregnant women are entitled to three times to pass a free ultrasound. Usually, they are administered between 11 and 14 weeks, between 18 and 22, and between 32 and 34. Each of these ultrasound pursues his goal (the first was to determine a gross fetal malformations and genetic anomalies, the second – overseeing the development of internal organs, the third determination condition of the placenta, fetal position and estimated weight). However, whenever the study doctor determines how many weeks the fetus is developed. And often, this term ahead of the obstetric. For example, a woman knows that her pregnancy is 20 weeks and the doctor pointed to the conclusion that the size of the fetus correspond to the 22 weeks. Why there is such situation? No mistake in it. This can be explained as follows:

  • The large fruit. The large size of the fetus ahead of his gestational age, is not a pathology. Similarly, like all people, the fetus already in the womb has its own individual characteristics.
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  • The size of the fetus is slightly smaller than it should be. This may be a normal variant, maybe baby is just small, especially if parents do not differ high growth and impressive weight.
  • Incorrectly identified obstetric weeks. There are cases when bleeding occurs, the woman takes over next month, is actually the threat of miscarriage in having already occurred in the previous cycle of pregnancy. In people, this phenomenon is called «the washing of the fruit.» It turns out that the woman calls the doctor the same date your last period, assuming that conception occurred in this cycle, whereas in fact it happened in the previous one and accordingly, an obstetric term will be longer.

As ultrasound is often wrong?

There is always a probability of error as more or less the determination of the term at ultrasound. Why is this happening and how many factors to blame for this? Several of them: outdated equipment, insufficient qualification of the doctor of functional diagnostics, confusion with the date of the last menstruation, did not immediately see the fruit, the individual characteristics of the fetus (too large or too small). You can minimize the risk of error. It is enough to visit the medical centers in which the level of training of doctors and quality of equipment is not in doubt, and to carefully monitor your cycle and know exactly the date of the last menstrual period.