Pregnancy Ultrasound Types: Complete Scan Guide

Pregnancy ultrasounds are an essential part of prenatal care, providing valuable information about your baby's development and well-being. From confirming the pregnancy to assessing fetal anatomy, different types of ultrasound scans are performed throughout your pregnancy. This guide will walk you through the common pregnancy ultrasound types, including the dating scan, NT scan, anomaly scan, growth scan, and Doppler scan, explaining what each scan checks and when it's typically performed, with costs relevant to Chennai.

What Is Ultrasound and Why Is It Done

Ultrasound imaging, also called sonography, uses high-frequency sound waves to create real-time images of the inside of your body. In obstetrics, ultrasound is a non-invasive and safe method to monitor the progress of your pregnancy. The sound waves bounce off the baby and other structures, and these echoes are then converted into images on a screen. With ultrasound, the brighter or whiter an ultrasound image is, the more dense that tissue is.

Pregnancy ultrasounds are performed for various reasons, including:

• Confirming pregnancy: To verify a pregnancy and rule out ectopic pregnancies.
• Determining gestational age: To accurately estimate the due date.
• Detecting multiple pregnancies: To identify twins, triplets, or more.
• Assessing fetal growth: To monitor the baby's development and identify any growth restrictions.
• Screening for anomalies: To check for structural abnormalities in the baby's organs and body parts.

According to the WHO, every pregnant woman should have at least one ultrasound before 24 weeks to estimate gestational age, detect fetal anomalies and multiple pregnancies, and improve the overall pregnancy experience.

Dating Scan: Confirming Pregnancy and Estimating Due Date

The dating scan is usually the first ultrasound you'll have, typically performed between 6 and 9 weeks of pregnancy. This early scan has several important purposes:

• Confirming the pregnancy: The primary goal is to confirm that you are indeed pregnant and that the pregnancy is located within the uterus. This helps rule out an ectopic pregnancy, where the fertilised egg implants outside the uterus, which can be life-threatening. ESHRE emphasizes the need for a clear definition of a normally sited pregnancy on ultrasound to avoid misdiagnosis of uterine ectopic pregnancies.
• Determining gestational age: By measuring the size of the gestational sac and the embryo, the sonographer can estimate how far along you are in your pregnancy and provide a more accurate due date. This is especially helpful if you're unsure of your last menstrual period or have irregular cycles.
• Detecting multiple pregnancies: The dating scan can also reveal if you're expecting twins, triplets, or more. Identifying multiple pregnancies early on allows for specialised prenatal care and monitoring.
• Checking for a heartbeat: The sonographer will also check for the presence of a fetal heartbeat, which is a reassuring sign of a viable pregnancy.

In my clinical experience, patients find the dating scan particularly reassuring as it provides visual confirmation of their pregnancy and allows them to see their baby for the first time. The cost of a dating scan in Chennai typically ranges from ₹1500 to ₹2500.

NT Scan: Screening for Chromosomal Abnormalities

The Nuchal Translucency (NT) scan is a screening test performed between 11 weeks 2 days and 14 weeks 1 day of pregnancy. It is often combined with a blood test (maternal serum screening) to assess the risk of certain chromosomal abnormalities, such as Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13). NICE guidelines recommend offering this scan to all pregnant women.

During the NT scan, the sonographer measures the nuchal translucency, which is the fluid-filled space at the back of the baby's neck. All babies have some fluid in this area, but an increased amount of fluid can indicate a higher risk of chromosomal abnormalities.

The NT scan is a screening test, not a diagnostic test. This means that it can only estimate the risk of chromosomal abnormalities, not definitively diagnose them. If the NT measurement is higher than normal, further diagnostic testing, such as chorionic villus sampling (CVS) or amniocentesis, may be recommended to confirm the diagnosis.

It's important to remember that a normal NT scan does not guarantee that the baby is free of chromosomal abnormalities. However, it can provide valuable information to help you make informed decisions about your prenatal care. The cost of an NT scan in Chennai typically ranges from ₹2000 to ₹3500.

Anomaly Scan: Detailed Assessment of Fetal Anatomy

The anomaly scan, also known as the mid-pregnancy scan, is a detailed ultrasound performed between 18 weeks 0 days and 20 weeks 6 days of pregnancy. It's one of the most important ultrasound scans as it allows the sonographer to examine the baby's anatomy in detail and check for any structural abnormalities. NICE guidelines recommend offering this scan to all pregnant women.

During the anomaly scan, the sonographer will assess various parts of the baby's body, including:

• Brain: To check for any abnormalities in the brain structure.
• Face: To look for cleft lip or palate.
• Spine: To ensure the spine is properly formed.
• Heart: To assess the heart's structure and function.
• Lungs: To check for proper lung development.
• Kidneys: To ensure the kidneys are functioning correctly.
• Limbs: To check for any abnormalities in the arms, legs, hands, and feet.
• Abdominal Wall: To detect any defects like omphalocele.

The anomaly scan can detect many, but not all, structural abnormalities. Some abnormalities may not be visible on ultrasound until later in pregnancy or may not be detectable at all.

If an abnormality is detected during the anomaly scan, further investigations, such as additional ultrasounds, fetal MRI, or genetic testing, may be recommended. Early detection of abnormalities can help healthcare providers plan for appropriate management and care after birth. The cost of an anomaly scan in Chennai typically ranges from ₹3000 to ₹5000.

Growth Scan: Monitoring Fetal Growth and Well-being

Growth scans are typically performed in the third trimester of pregnancy, usually after 28 weeks. These scans are used to monitor the baby's growth and assess their overall well-being. Growth scans are often recommended if there are concerns about the baby's size, such as if the baby is measuring too small or too large, or if you have certain medical conditions, such as gestational diabetes or high blood pressure.

During a growth scan, the sonographer will measure various parameters, including:

• Biparietal diameter (BPD): The diameter of the baby's head.
• Head circumference (HC): The circumference of the baby's head.
• Abdominal circumference (AC): The circumference of the baby's abdomen.
• Femur length (FL): The length of the baby's thigh bone.

These measurements are then compared to standard growth charts to assess whether the baby is growing at an appropriate rate.

Growth scans can also help assess the amount of amniotic fluid surrounding the baby. Too little amniotic fluid (oligohydramnios) or too much amniotic fluid (polyhydramnios) can indicate potential problems.

Doppler Scan: Assessing Blood Flow to the Baby

A Doppler ultrasound scan is a non-invasive test that uses sound waves to assess blood flow in different parts of the baby's body and in the placenta. It's often performed in conjunction with a growth scan to provide a more comprehensive assessment of the baby's well-being, especially in high-risk pregnancies. A meta-analysis has shown the importance of Doppler parameters in pregnant women with hypertensive disorders.

Doppler scans can measure blood flow in:

• Umbilical artery: To assess blood flow from the placenta to the baby. Abnormal umbilical artery pulsatility index (UA PI) is associated with a higher risk of low birth weight.
• Middle cerebral artery: To assess blood flow to the baby's brain.
• Uterine arteries: To assess blood flow to the uterus. Abnormal uterine artery resistance index (UtA RI) is associated with a higher risk for fetal growth restriction.

Abnormal blood flow patterns can indicate that the baby is not getting enough oxygen or nutrients, which may require further intervention.

Here's a comparison of the different pregnancy ultrasound types:

Disclaimer: These are approximate ranges for Chennai in 2026 — your actual cost will depend on the facility and specific requirements.

Pregnancy Ultrasound Types and Costs in Chennai

The cost and availability of pregnancy ultrasound scans in Chennai can vary between facilities. Most major hospitals and diagnostic centres in areas like Egmore, Mylapore, T Nagar, and Tambaram offer the full range of scans listed above. When choosing a facility, consider factors like the experience of the sonographer, the quality of the ultrasound equipment, and whether the facility provides detailed reports that your obstetrician can use for ongoing care. Many patients at our practice across Chennai find it helpful to have all scans done at one facility for consistency in measurements and tracking.

Practical Tips and Daily Recommendations

While pregnancy ultrasounds are an essential part of prenatal care, there are also steps you can take to support a healthy pregnancy:

• Attend all scheduled prenatal appointments: Regular check-ups with your obstetrician are crucial for monitoring your health and your baby's development.
• Eat a healthy diet: Focus on nutrient-rich foods, including fruits, vegetables, whole grains, and lean protein. Consider reading our guide on baby brain development food during pregnancy.
• Take prenatal vitamins: Prenatal vitamins help ensure you're getting enough essential nutrients, such as folic acid, iron, and calcium.
• Stay active: Regular exercise, such as walking or swimming, can help improve your overall health and well-being during pregnancy.
• Avoid harmful substances: Avoid smoking, alcohol, and illicit drugs, as these can harm your baby.
• Stay hydrated: Drink plenty of water to stay hydrated and support amniotic fluid levels.

When to Seek Professional Help

Pregnancy ultrasounds are a valuable tool for monitoring your baby's development and well-being. If you have any concerns about your pregnancy or the results of your ultrasound scans, it's essential to discuss them with your healthcare provider. For personalised guidance, book a consultation with Dr. Rukkayal Fathima.