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All you want to know about ultrasound during pregnancy by Dr. Rachita Gupta

Ultrasound is an integral part of every pregnancy. For the parents, this is an exciting moment as they get a glimpse of their baby and hear the heartbeat for the first time. But along with the excitement, there is a lot of anxiety too, especially for first-time parents who have a whole list of questions about the pregnancy and all that it involves.

So, here are answers to some commonly asked questions.

Is Ultrasound safe?

Ultrasound scans are non-invasive and have been in use for more than 40 years to track pregnancies. Over the years several studies have been conducted to check if these scans can harm the fetus but no link has been found on its impact on the birth weight, eyesight, hearing, behavior, intelligence and cancers in the baby.

That said, it’s important to remember that there should be clear medical reasons for doing a scan, and all ultrasound exposure should be justified and limited to the minimum needed to make a diagnosis.

Why is it required?

• To confirm the location of the developing baby (is the fetus inside the uterus or outside)
• To check for the number of fetuses
• To check the heartbeat
• To see if there’s any risk of Down’s syndrome or other chromosomal abnormality
• To see the fetal structure to check if there are any anomalies
• To check the position of the placenta
• To check on the growth of the fetus
• To check if there are any complications and their potential impact on the fetus
• Helps in guided procedures like CVS (a prenatal test done to check for birth defects or genetic diseases) or amniocentesis (a medical procedure to check for chromosomal abnormalities and fetal infection), if needed

How Many scans are usually done?

The routine scans usually are:

• Dating and viability scan between 6 and 9 weeks.
• Early morphology (NT/NB scan) between 11 and 13 weeks.
• Anomaly scan (ultrasound level II) between 18 and 22 weeks.
• Growth scan or fetal wellbeing scan between 28 and 32 weeks.
• Growth scan and color Doppler studies between 36 and 40 weeks.

More scans may be needed if there are any conditions complicating the pregnancy like :

• High blood pressure, gestational diabetes, thyroid disorders
• Any other significant previous medical history
• Twin/multiple pregnancies
• Suspected growth restriction
• Bleeding or leaking during pregnancy
• Increased or decreased levels of amniotic fluid
• Trauma during pregnancy

When should the first scan be scheduled?

Typically between 6-9 weeks to confirm that the fetus is located within the uterus and that the baby has a heartbeat.

This is known as the dating scan and is used to calculate the age of the baby which then becomes the reference age during the pregnancy to assess the fetal growth.

How many types of ultrasound are available?

Pregnancy ultrasound can be done in two different ways.

• Trans Abdominal (standard) ultrasound: – Transabdominal ultrasound provides a complete view of the abdomen and pelvis. It involves gliding a transducer across your abdomen to create two-dimensional images of your baby and internal organs.

• Trans Vaginal Ultrasound: -TransVaginal ultrasound provides a more limited but better pelvic view and requires inserting a probe into the vagina.

• 3D/4D: A 3-D ultrasound uses computer software along with a specially designed transducer to generate a complete 3-D picture of the baby.
4-D ultrasound is a dynamic 3-D ultrasound. Expecting parents enjoy this as they can see the baby moving and doing various actions within the womb.

• Doppler: can be done trans-abdominally or transvaginally. IIt measures the blood flow from the mother to the baby, through the umbilical cord and to the baby’s brain and heart. It helps to understand the oxygen and nutrients supply to the baby via the placenta.

• Fetal Echo: provides a detailed examination of the fetal heart. It is usually required if there is any abnormality in the fetal structure, irregularity of heartbeat, high risk of fetal abnormalities on the blood test, history of parents or siblings with cardiac defects or any other complications of pregnancy that affect the fetus.

How to prepare for an ultrasound?

• No special preparation is required for these ultrasounds. It is better to wear clothes that allow a comfortable access to your abdomen.
• Transabdominal scans in the first trimester are usually done with a full bladder. A full bladder is not necessary for scans later in the pregnancy.
• The transvaginal scan is done with an empty bladder.
• You do not need to be fasting or empty stomach for the pregnancy ultrasounds.

Who will do my ultrasound scan?

In India ultrasound can only be performed by radiologists who have a post-graduate degree and are registered WHERE/WITH WHAT ORGANISATION under the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act. It has to be done in a clinic/hospital/ diagnostic center that is registered under PCPNDT Act and follows its guidelines.

How accurate is ultrasound in calculating gestational age?

Usually, the pregnancy is confirmed by the BETA HCG levels in the body (HCG is a hormone produced during pregnancy) and the date of your last menstrual period. However, due to variation in each woman’s cycle, there may be the difference in the gestational age calculation. So the gestational age according to the first ultrasound (dating scan) is considered to be most accurate and is used during the subsequent scans to track the growth of the baby.

What does the ultrasound report show?

The ultrasound report will have a print of your baby’s images and a page showing the parameters measured for the baby’s growth. However, it is important to remember that the main purpose of the scan is to assess the baby’s growth and not to provide the first photo for your baby album.

In India determining the sex of the baby is a criminal offense punishable by law for the doctor conducting the ultrasound and also for the patient who wants to know the sex of the baby. It is illegal for any doctor to tell you whether you are expecting a son or daughter.

Dr. Rachita Gupta

Consultant - Obstetrics and Gynecology

Panchsheel Park