Ultrasound, sometimes called a sonogram or sonography, is a non-invasive test that uses high-frequency sound waves to create an image of the baby while it is in the uterus.
Ultrasound is a valuable tool that is used by doctors to confirm the age of the fetus, whether there are multiple fetuses and to confirm whether the major physically structures of the baby are developing normally. The test is often performed in your doctor's office, although you may be asked to go to the hospital so that it can be administered by a radiologist. If the test is looking for a specific problem, your doctor will recommend that it is performed by a specialist.
Your doctor can also use ultrasound to locate the position of the fetus and the placenta while performing another test such as amniocentesis, or to confirm or rule out the presence of placenta previa or placental abruption. Images created using ultrasound can be difficult to interpret, requiring the skills of an experienced operator. Ask your doctor to explain what you are seeing on the screen.
Ultrasound uses high-frequency sound waves generated by a transducer, which pass through fluid and are reflected by objects such as tissue. This pattern of echoes is then converted into electrical signals, which are displayed on a screen.
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There are two methods that can be used to create an ultrasound during pregnancy. If the ultrasound is performed before week twelve, a vaginal probe ultrasound may be performed. This uses a thin instrument that is placed in the vagina, providing a clear image of the fetus, uterus, ovaries and fallopian tubes. While it sounds unpleasant, the probe is more comfortable than a pelvic exam using a speculum.
After week twelve you are likely to receive an abdominal ultrasound. A water-based and non-staining gel that helps conduct sound waves is rubbed over your stomach. A transducer, a device that looks like the mouse of your computer, is passed over your stomach, creating an image of the baby.
Because the bladder lies in front of the uterus, your doctor will recommend that it is full before performing the abdominal ultrasound. This pushes your bladder out of the pelvis making it easier to view. If necessary you will be asked to drink about 32 fluid ounces (960 ml) of water before the procedure. Sometimes the position of the baby or the uterus makes it impossible to generate a clear image of the baby. The operator may suggest that an additional scan is necessary, but this does not mean that anything is wrong. It is better to ask for an explanation, than to go home and worry in silence.
It is common for operators to quietly perform the ultrasound, while examining the images. This can be disconcerting if you are wondering what they are looking for. If you are worried about what they are seeing, ask the operator to interpret the images on the screen so that you can visualize the development of your baby while the scan is being performed.
Some ultrasound machines are capable of recording the session on videotape. Many new parents like to have a copy of the video or a printed image from the machine of their new baby before it is born. Even if a video can be made, your partner will probably want to come with you so that you can both view the pictures of your baby. Not all machines can produce a video, although most can print pictures, so you should ask your doctor if the test can be recorded and if you should be a blank tape with you. And find out about bringing other members of your family!
An ultrasound is now considered a routine part of pregnancy, and is used to confirm or estimate your due date. Ultrasounds are often used to determine if you are carrying multiple fetuses, and ensure that the main physical structures of the baby are developing normally. Not all insurance companies cover routine ultrasound, and you should check your policy before you schedule the test.
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While ultrasound is mostly used for routine pregnancies, the procedure can also be used to identify problems. A nuchal scan is a recent innovation that can help screen for Down's syndromeA congenital abnormality in which the baby is born mentally retarded, with an average IQ of 50 - 60 and with physical deformation of the face (low set ears, sloping forehead, mongoloid eyes), and shortness of stature.
Downs syndrome is caused by an extra chromosome 21 present in the G group. In a small percentage of cases it can be caused by the switching of chromosomes 14 or15 in the D group or chromosome 21 or 22.
Down's syndrome occurs in about 1 in 650 births, and is more commonly associated with children of mother's over the age of 35. Incidence in children of mothers over the age of 40 can be as high as 1 in 80.
Down's syndrome can be detected prenatally through amniocentesis. The mortality rate is high within the first few years. Down's syndrome is also known as mongolizm, trisomy 21 or trisomy G syndrome.
Visit our comprehensive glossary for more pregnancy terms and definitions.. Other fetal abnormalities such as hydrocephalusA congenital abnormality in which excessive fluid collects on the brain enlarging the skull. Surgical treatment with a survival rate greater than 80% involves a combination of procedures including correction of the ventricular obstruction, reduction of the production of cerbralspinal fluid and the installation of shunts to drain excess fluid to the right atrium of the heart or peritoneal cavity.
Visit our comprehensive glossary for more pregnancy terms and definitions., or obstetric problems such as the position of the placentaThe placenta is a large disk shaped membrane responsible for providing nourishment to the fetus during pregnancy. It consists of three parts, the fetal part made up from the chorion membrane surrounding the fetus, the maternal part, formed from the decidua basalis layer of the uterine lining, and the intervillous space between the two plates. It is connected to the fetus by the umbilical cord and consists of tissue from both the mother and the embryo.
Its function is complex. It has been described as a simple organ that combines the functions of a kidney-dialysis machine, heart and lung machine and intravenous drip. It consists of enormous numbers of blood vessel branches that permit the exchange of nutrition and oxygen, from the mother's bloodstream to the fetus and the removal of wastes to the mother to be excreted. The placenta's remarkable quality is that it does so without the blood of the mother mixing with that of the baby.
It also is responsible for the production of vital hormones including, estrogen, progesterone, and human chorionic gonadotropin. After birth, the placenta is delivered, and is sometimes referred to as the afterbirth.
Visit our comprehensive glossary for more pregnancy terms and definitions. or volume of amniotic fluidThe liquid, which is produced by both the fetal membranes and the fetus that surrounds the baby during pregnancy. The liter of fluid at term serves to protect the fetus during pregnancy and also provide active chemical exchange.
The amniotic fluid consists of maternal and fetal plasma in varying concentrations. The pH of the fluid is almost neutral and clear, although lipids and desquamated fetal cells can make it cloudy.
Visit our comprehensive glossary for more pregnancy terms and definitions. can also be determined.
Ultrasound is also a valuable tool for doctors performing other tests such as amniocentesis, to help locate the position of the fetus and placenta before inserting the needle into the uterus. If the ultrasound is performed after week eighteen, it may be possible to identify the sex of the baby, but this is still an inexact science, and should not be used as the basis for buying baby clothes and decorating the nursery!
The risks of ultrasound during pregnancy have been thoroughly researched. Most experts agree that the procedure is safe, both for you and your baby.
Depending on your doctor, your pregnancy and your insurance plan, you may receiving one, two or regular ultrasounds throughout your pregnancy. A simple dating
If the ultrasound is to be used for fetal anomaly scanning, or to help perform an amniocentesis it will be undertaken between week sixteen and week twenty two. If you are experiencing urinary tract or kidney problems, or if your doctor suspects placenta previa, then the scan may be performed after week thirty.
You can watch the images of your baby moving in the uterus while the test is being performed. Ask questions and get the operator to explain the images that you are both watching on the screen.
If the ultrasound has indicated that your baby is not developing as expected, additional tests may be required to confirm or rule out the diagnosis. Ask your doctor for a thorough explanation if results of the test are unclear.
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