Ultrasonography in Pregnancy
What is an ultrasound scan?
An ultrasound scan involves transmitting high frequency sound waves through the uterus. These bounce off the baby and the returning echoes (sound waves) are translated by a computer into an image on a screen that reveals the baby’s position and movements.
Why do I need an ultrasound scan?
Ultrasound has been used in pregnancy for about 30 years, it has progressively become an indispensable obstetric tool and plays an important role in the care of every pregnant woman.
The common reasons for your doctor to request an pregnancy ultrasound scan are:
• To establish the date when the baby is due.
• To check the number of babies.
• To establish that the pregnancy is continuing normally.
• To show the position of the placenta.
• To check the physical development of the baby and to check for birth defects.
• In later pregnancy, to see that the baby has grown appropriately for its stage of development
Who will do the scan?
Scans are usually performed by a doctors, midwives or radiographers who are specially trained in ultrasound, and are known as sonographers. Most have completed a post graduate Certificate, Diploma or Master’s degree in Medical Ultrasound.
When scans are usually carried out in antenatal period?
The JIJAI WOMEN’S HOSPITAL Provide ultrasound screening for pregnant women and fetuses at risk for pregnancy-related complications by offering diagnostic ultrasound scans to detect fetal and placental abnormalities throughout pregnancy. Your first-trimester ultrasound, commonly performed to evaluate the risk of genetic abnormalities, has allowed for the early detection of some major abnormalities before the second trimester.
The range of fetal ultrasonography services include:
• First and second trimester Down syndrome screening
• Miscarriage and ectopic pregnancy screening
• Multiple pregnancy screening
• Fetal anomaly screening
• Assessment and Evaluation
• First trimester evaluation
• Second and third trimester anatomical assessment
• 3-D ultrasound evaluation
• Prenatal diagnosis
• Testing and monitoring
• Biophysical profile and Doppler velocimetry/non-stress testing
• Fetal echocardiography
• Diagnostic Procedures
• Chorionic villi sampling (CVS)
• Cordocentesis/Fetal blood sampling
Five, six or seven weeks:
Ultrasound for Size and Dates: Dating based on your last menstrual period can be very inaccurate. Ultrasound done early in the first trimester allows for accurate dating of the pregnancy. Since the fetus (baby) is extremely small, it also allows for better visualization of maternal structures (uterus, ovaries, and fallopian tubes), and gives us the ability to detect any abnormalities very early. However, if this ultrasound is performed too early (before 7 weeks gestation), the fetus may not be developed enough to get all of the information needed and you may be asked to return in 1-2 weeks. If you are experiencing pain or bleeding for example. This may rule out an ectopic pregnancy. You may have your first scan if unsure of the date of LMP.
NUCHAL TRANSLUCENCY SCAN (11-14 wks)
The 12 week scan is a routine ultrasound examination carried out at 10 to 14 weeks of gestation. During the examination, the fetus is seen by abdominal ultrasound. Occasionally the view is not clear and it may be necessary to perform a vaginal scan. At the first trimester scan they confirm that the fetus is alive, they assess the gestational age by measuring the crown-rump length and will also look for any major problems.
10 to 14 weeks:
The NT is a non-invasive screening ultrasound that is used in the 1st trimester to detect Down syndrome, trisomy 18, or other problems. The results of the nuchal translucency screening are then combined with those of 2 blood tests and the mother’s age to assess the risk for the fetus. Since there is only a very short window to obtain the necessary measurements, it is extremely important that we have accurately dated the pregnancy with a size/dates ultrasound first. It is recommended that all pregnant women have a dating scan in the first trimester at around 12 weeks of pregnancy to confirm their dates. First trimester ultrasonic scans may show ‘soft’ markers for chromosomal abnormalities, such as the absence of fetal nasal bone, an increased fetal nuchal translucency (back of the neck) to enable detection of Down syndrome fetuses.
About 18 – 20 weeks:
Some women are offered a scan in the second trimester at around 18 to 20 weeks. Known as the anomaly scan or Level II to check that your baby is developing normally. A scan performed at 18 to 20 weeks the fetus is large enough for an accurate survey of the fetal anatomy. Congenital malformations, multiple pregnancies can be firmly diagnosed and dates and growth can also be assessed. Placental position is also determined. Further scans may be necessary if abnormalities are suspected.
Colour Doppler Scan (About 28-32 wks):
Doppler Ultrasound gives doctors a visual or audible representation of blood movement through veins, arteries and blood vessels with sound waves. The reflected sound can be used to diagnose restricted blood flow, blood clotsand fetal health. Unlike ultrasound imaging used to give parents apicture of baby in-utero, Doppler Ultrasound is used to view blood flow in the fetus. Doppler Ultrasound tests are conducted with a handheld device known as a transducer. There are three main types of Doppler Ultrasound – Continuous, Duplex and Color.
Why Is Doppler Ultrasound Used During Pregnancy?
There are various diagnostic uses for Doppler Ultrasound in a traditional medical setting, but in terms of pregnancy and fetal and pregnancy health, uses are limited. Doctors often use Doppler Ultrasound during pregnancy to check fetal umbilical blood flow, placental blood flow and blood flow in the heart and brain. Using the Doppler Ultrasound results, doctors can determine if restricted blood flow due to sickle cell anemia, RH sensitization or restricted blood vessels is to blame for fetal abnormalities.
Restricted blood flow to the fetus could cause:
• Lower birth weight
• Reduced size
• Impaired development
If sickle cell anemia is diagnosed, children may undergo a special form of Doppler Ultrasound known as the Transcranial Doppler to evaluate risk of stroke.
28 to 40 weeks:
Growth scans in the third trimester may be recommended if a previous baby was small, if you are having twins or when there are other complications of pregnancy, for instance if you are diabetic. Sometimes your midwife may suggest a growth scan if the baby feels and measures smaller or larger than expected.
There is no hard and fast rule for the number of scans you should have during pregnancy.
A scan maybe ordered when an abnormality is suspected on clinical grounds. Otherwise a scan is generally booked in the first trimester to confirm pregnancy, exclude ectopic or molar pregnancies, confirm cardiac pulsation and measure the crown to rump length for dating.
What to expect from a3D Scan?
You will receive at least four colour portrait prints, and at least two black and white portrait prints. These portrait prints are further complemented with between 10-20 colour images on CD, suitable for emailing and printing to share with all the family. In addition, throughout the whole scan, a DVD is recorded of any movement the baby makes.
When to have a 3D Scan?
While there is no problem performing the 3D scan at any stage of your pregnancy, in order to get the best images, we perform the 3d scan between 22 and 32 weeks of pregnancy, although we advise that the optimum time is between 24 and 29 weeks. The timing of the scan is really a balancing act, as you want baby to be as big as possible so you get to see as much as you can, but you still want your baby to have plenty of room to move around.
The 3D Scan / 4D scan is optional and does not replace your maternity hospital scan, as it is not intended to provide diagnostic information but to enhance parental enjoyment and bonding.