How exactly is an ultrasound sex

Pregnancy: how reliable is the ultrasound?

Ultrasound: gender not recognized by baby

"As early as the 13th week of pregnancy, my gynecologist wanted to know that I was going to have a son. In the 38th week of pregnancy, she estimated the baby's weight at 4,000 grams. Well, it wasn't a boy, but a girl. And she weighed only 3,200 grams, "says Cornelia Blankenberg. * Women repeatedly report such experiences with pregnancy ultrasound. But how do these errors come about? And how reliable are other important predictions, for example whether the baby is growing sufficiently and developing in a timely manner, or whether there are signs of illness or disability?

Big differences in ultrasound machines

A doctor's equipment is a first important point in terms of accuracy. Because not all ultrasound devices are the same. First of all, there are the "normal" devices used by the resident gynecologist. It is important for the accuracy whether the device is twelve years old or just one year old. Then there are the high-resolution (and correspondingly more expensive) devices, such as those in special practices for prenatal diagnostics.

The 3-D or 4-D ultrasound, which is so popular with parents, shows an almost life-like, three-dimensional image of the baby, but "in most cases these devices have no diagnostic advantages," explains Professor Annegret Geipel from the board of the German Society for ultrasound in medicine (DEGUM) in conversation with urbia. "Some doctors believe that they can be helpful in examining certain abnormalities more closely. As a rule, however, they primarily meet the parents' wish to see their baby more realistically," said Geipel, who heads the university's prenatal medicine department -Frauenklinik Bonn.

The higher the qualification, the more reliable the forecasts

However, the ultrasound machine used is only as good as the doctor who uses it. The accuracy of the predictions therefore also depends on the training of the gynecologist. Obstetricians and gynecologists can be certified for recognition by DEGUM. Depending on the requirements, there are levels DEGUM I, II and III. Most of the established gynecologists do not have DEGUM approval.

For DEGUM I approval for pregnancy ultrasound, a doctor must prove experience with biometric measurements of the child and with the representation of certain organs between the 19th and 22nd week of pregnancy. He must now also recognize so-called signs of malformations and be able to assess the uterus, the amount of amniotic fluid and the placenta. Most points can also be examined by a doctor without DEGUM I approval during the extended basic ultrasound (second trimester of pregnancy), but must be guided by the requirements of DEGUM level I.

For level DEGUM II, a doctor needs particularly high-resolution ultrasound devices (and a Doppler device), has to prove experience in diagnosing malformed fetuses and has to pass certain exams. DEGUM II mainly have doctors in special practices for prenatal medicine. Level III can only be achieved by highly specialized doctors in large prenatal medicine centers.

How safe is sex determination?

But how reliably does the ultrasound answer the burning questions of parents-to-be? When it comes to the sex of the child, the following applies: "With normal preventive ultrasound, the reliability of gender determination between the 16th and 20th week of pregnancy is around 90 percent. With fine ultrasound, it is around 80 percent from around the 13th week of pregnancy and is around 20th week as good as certain. The prerequisite is always that the child is lying down comfortably, "explains Prof. Annegret Geipel.

How heavy will the child be?

"When I was in the 22nd week for fine ultrasound in a special practice, the doctor estimated the birth weight of my baby at 4,000 grams. And it was almost correct, my son weighed 3,940 grams at delivery," says Astrid Rheindorf from Wuppertal. But the normal gynecologist does not achieve the accuracy of this doctor with DEGUM II status so early: "At the time of the three basic examinations, ie around the 10th, 20th and 30th week of pregnancy, no reliable estimate of the birth weight is possible. Only towards the end pregnancy, when the gynecologist does another ultrasound or the pregnant woman presents to the maternity hospital, an estimate makes sense, "explains Prof. Geipel.

The modern ultrasound devices are already equipped with software for determining the birth weight. "Here there is still an average deviation of plus / minus ten percent, which corresponds to around 300 to 400 g," says Geipel. If a woman is already in labor at the time of the examination, the accuracy of the estimate may decrease.

Ultrasound in early pregnancy

Another question that concerns all parents-to-be: will our baby be healthy? An early ultrasound examination for this is the measurement of the neck folds between the 11th and 14th week of pregnancy. It can give an indication of a possible trisomy 21 (Down syndrome) as well as other malformations or diseases. A trisomy 21 is detected with a certainty of about 75 percent. Conversely, many babies with noticeable neck transparency are still healthy, so couples should have the result well explained.

In this measurement, however, a tenth of a millimeter counts. If her own gynecologist offers neck wrinkle measurement, a pregnant woman should make sure that he has sufficient experience: "The pregnant woman should ask her doctor about his qualifications. He should be licensed by the Fetal Medicine Foundation (FMF) London or the FMF Germany", emphasizes Prof Geipel.

Are malformations reliably detected?

How reliably are malformations detected in ultrasound? With the three BaseThe following applies to examinations during pregnancy: "For minor malformations, the reliability is around 30 to 40 percent, for severe malformations around 60 percent," says Geipel. "If the gynecologist is unsure about a sign of a malformation or if he finds it difficult to visualize an area during his examination, he will refer a pregnant woman to a specialist for a fine ultrasound," explains Geipel. In the case of fine ultrasound, the all-clear is given in around three quarters of the cases.

Conversely, even with high-resolution devices, not all malformations can be detected before birth (experts assume a hit rate of 80 to 90 percent), and in many diseases there are no externally recognizable changes.

Fine ultrasound - preferably with experience!

Sometimes gynecologists offer the fine ultrasound in their own practice. Here, too, women shouldn't be afraid to ask about their qualifications. "There are only a few established gynecologists without DEGUM certification who have a corresponding other qualification. As a rule, examiners specializing in prenatal ultrasound are DEGUM-certified," explains Prof. Geipel. There is one exception, however: even doctors without DEGUM II approval can carry out a fine ultrasound examination after taking an examination at the Association of Statutory Health Insurance Physicians and bill the health insurance company for this.

If her doctor does not have DEGUM approval, a pregnant woman can consider going to a special practice in order to increase the reliability of the examination. Because when diagnosing malformations, for example, "the reliability is highly dependent on the experience of the examiner. However, malformations only occur very rarely in normal practice. Therefore, women can make use of the detailed diagnosis as a self-payment service in a special practice for prenatal medicine." explains Prof. Geipel.

How sure do you know whether the child is developing well?

But parents also want to know whether their unborn baby is doing well. It is true that the aforementioned fine ultrasound also examines whether the blood flow via the umbilical cord is optimal or the placenta does not show any abnormalities - which could otherwise lead to an undersupply of the child later. The three regular pregnancy ultrasound scans provide little security here: "Growth retardations (delays) can sometimes be seen earlier, but they usually only appear in late pregnancy and are only then detected. The reason is that they are often caused by a declining pregnancy Function of the mother cake, as it usually only comes into play towards the end of pregnancy, "explains Prof. Geipel. Nevertheless, women can rest assured: To be on the safe side, almost all gynecologists do another ultrasound examination in late pregnancy.

*Name changed

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