Pregnancy is an exciting journey, but it naturally comes with plenty of questions. One of the most common concerns for expectant parents is understanding which pregnancy ultrasonography tests are needed, when they should be performed, and what each scan reveals about the developing baby.
Pregnancy ultrasonography, commonly called a pregnancy USG or ultrasound scan, is an imaging test that uses high-frequency sound waves to create pictures of the developing baby inside the uterus. It helps doctors assess the progress of pregnancy, estimate the baby’s age, examine fetal development, and identify certain pregnancy-related complications.
Different ultrasound scans serve different purposes. An early pregnancy scan may help confirm the location of the pregnancy, while an anomaly scan examines the baby’s developing organs and a growth scan assesses fetal growth later in pregnancy.
Understanding the purpose and timing of these tests can help you prepare for antenatal appointments and make informed decisions with your doctor.
What is pregnancy ultrasonography?
Pregnancy ultrasonography is a medical imaging procedure used to examine the uterus, placenta, amniotic fluid and developing fetus during pregnancy.
During the examination, an ultrasound machine sends sound waves into the body through a device called a transducer. These waves bounce off internal structures and return to the machine, which converts them into images.
Unlike X-rays, ultrasound does not use ionising radiation. Diagnostic ultrasound is generally considered safe when performed by trained professionals for appropriate medical reasons.
Your doctor may recommend an ultrasound to:
- Confirm the location of the pregnancy.
- Estimate gestational age and calculate the expected delivery date.
- Check the baby’s heartbeat when appropriate for the stage of pregnancy.
- Determine whether you are carrying one baby or multiple babies.
- Examine fetal growth and development.
- Assess the placenta and amniotic fluid.
- Evaluate the baby’s position.
- Examine blood flow using Doppler ultrasound when indicated.
- Investigate certain symptoms or suspected pregnancy complications.
It is important to remember that ultrasound cannot detect every fetal abnormality or guarantee that a baby will be born without health problems. Your doctor interprets the findings alongside your medical history, examination and other recommended tests.
What are the four main types of pregnancy tests?
The term pregnancy test usually refers to tests that detect the hormone human chorionic gonadotropin (hCG). There are four commonly discussed approaches:
1. Home urine pregnancy test: An over-the-counter test that detects hCG in urine. It is convenient and is commonly used after a missed period.
2. Clinical urine pregnancy test: A urine test performed in a healthcare setting to check for hCG.
3. Qualitative blood hCG test: A blood test that indicates whether hCG is present at a detectable level.
4. Quantitative blood hCG test: Also called a beta-hCG test, it measures the amount of hCG in the blood. A doctor may recommend repeat measurements in certain situations.
These tests are different from pregnancy ultrasonography. Urine and blood tests detect a hormone associated with pregnancy, whereas ultrasound produces images that help doctors examine the pregnancy.
A positive pregnancy test is generally followed by medical consultation. Your doctor will determine whether an ultrasound is needed immediately or whether it is more appropriate to perform it after some time.
What are the two main types of ultrasounds used during pregnancy?
The two main methods of performing a pregnancy ultrasound are transabdominal and transvaginal ultrasonography.
1. Transabdominal ultrasound
During a transabdominal ultrasound, the sonographer applies gel to the abdomen and moves a transducer over the skin.
This method is commonly used for routine pregnancy scans, including many first-trimester examinations, anomaly scans and third-trimester growth scans.
Depending on the stage of pregnancy and the purpose of the examination, you may be asked to attend with a comfortably full bladder.
2. Transvaginal ultrasound
A transvaginal ultrasound uses a specially designed, covered transducer that is gently inserted into the vagina to obtain images from closer to the uterus.
It may be recommended during early pregnancy when the developing pregnancy is too small to assess clearly through an abdominal scan. It can help evaluate the location of the pregnancy, estimate gestational age and assess early pregnancy development.
The procedure may cause mild discomfort, but it should not be severely painful. Let the healthcare professional know if you experience pain or feel uncomfortable.
Your doctor will recommend the most suitable method based on your symptoms, gestational age and clinical requirements.
How many USG tests are needed during pregnancy?
There is no single number of ultrasound scans that applies to every pregnancy. The recommended schedule depends on local antenatal care practices, your medical history, pregnancy risk factors and the findings of earlier examinations.
Many pregnancies involve two principal screening scans, while others include an early dating scan and a third-trimester growth scan. Additional examinations may be recommended when clinically necessary.
Here is a general overview of commonly performed pregnancy ultrasonography tests.
First trimester: weeks 1–13
Early pregnancy or dating scan: approximately 6–8 weeks, when indicated
An early pregnancy scan may help establish whether the pregnancy is inside the uterus, assess early development, identify the number of embryos and estimate gestational age. The timing of visible structures and cardiac activity depends on the actual stage of pregnancy.
NT scan and first-trimester screening: approximately 11–13 weeks and 6 days
A nuchal translucency (NT) scan measures the fluid-filled space at the back of the baby’s neck. It may form part of a screening assessment for certain chromosomal conditions.
Depending on the screening programme and clinical advice, the assessment may be combined with maternal blood tests. Screening estimates the chance of particular conditions; it does not provide a definitive diagnosis.
Second trimester: weeks 14–27
Anomaly scan: generally 18–22 weeks
The anomaly scan, also known as the fetal anomaly scan or level II scan, is one of the most important ultrasound examinations during pregnancy.
It evaluates the development and structure of major fetal organs and body parts, including the brain, spine, heart, kidneys, abdominal structures and limbs, to the extent that they can be visualised.
The scan also assesses placental location, amniotic fluid and other features relevant to pregnancy care.
Fetal echocardiography: commonly around 18–24 weeks, when indicated
Fetal echocardiography is a specialised ultrasound examination of the baby’s heart. It provides a more detailed assessment of cardiac structure and function than a routine screening scan.
It may be advised when certain maternal, family or fetal risk factors are present, or when an abnormality is suspected during the routine scan.
Third trimester: weeks 28 until birth
Growth scan: commonly around 28–32 weeks or later, as advised
A growth scan measures fetal parameters to assess growth and estimate fetal weight. It may also examine the baby’s position, placental location and the amount of amniotic fluid.
Obstetric Doppler scan: when clinically indicated
A Doppler examination evaluates blood flow in selected blood vessels. It may be recommended when the doctor needs to investigate suspected fetal growth restriction, placental insufficiency or certain high-risk pregnancy conditions.
Not every pregnant woman needs every specialised scan. Your obstetrician will decide which examinations are appropriate for your pregnancy.
Which USG is done to confirm pregnancy?
An early pregnancy ultrasound may be used to confirm the location of a pregnancy and assess its development. A transvaginal ultrasound is often more informative than an abdominal scan during the very early weeks.
However, ultrasound is not usually the first test needed simply to find out whether you are pregnant. A urine pregnancy test or blood beta-hCG test can detect pregnancy earlier.
When a pregnancy test is positive, your doctor may recommend an ultrasound based on your last menstrual period, symptoms and medical history.
An ultrasound can help determine whether the pregnancy is inside the uterus. If a scan performed very early does not show a definite pregnancy, it does not automatically mean something is wrong. Repeat beta-hCG testing or a follow-up scan may be necessary.
Seek urgent medical attention if you have a positive pregnancy test accompanied by severe abdominal pain, shoulder-tip pain, fainting, marked dizziness or significant vaginal bleeding. These symptoms can indicate an ectopic pregnancy or another complication.
Can ultrasound detect a two-week pregnancy?
Usually, no. An ultrasound is generally too early to reliably visualise a pregnancy at two weeks when gestational age is calculated from the first day of the last menstrual period.
Pregnancy is conventionally dated from the last menstrual period, not from the date of conception. In a typical 28-day cycle, conception occurs around the time the pregnancy is considered two weeks along.
At this stage, there may not yet be a visible gestational sac on ultrasound. A urine or blood hCG test is generally more useful for detecting pregnancy around the expected period.
If your pregnancy test is positive, your doctor can advise you on the appropriate time for an ultrasound.
Will a three-week pregnancy show on ultrasound?
A pregnancy at three weeks by last-menstrual-period dating will generally not be clearly visible on ultrasound. This is because the pregnancy is still at a very early stage.
A blood beta-hCG test may detect pregnancy before an ultrasound can show a gestational sac. However, the timing of a positive result varies with ovulation, implantation and individual hormone levels.
If a scan is performed too early, the doctor may recommend waiting several days or arranging a follow-up examination. The goal is to obtain reliable information rather than draw conclusions from a scan performed before the pregnancy can be visualised.
When is the first ultrasound during pregnancy?
The timing of the first ultrasound depends on your clinical circumstances.
An early scan may be recommended at around 6–8 weeks when there is a need to confirm pregnancy location, assess early development, investigate pain or bleeding, or clarify dates.
In other uncomplicated pregnancies, the first planned ultrasound may be performed closer to 11–14 weeks as part of first-trimester assessment.
If you are unsure about your pregnancy dates, have irregular menstrual cycles or have experienced complications in a previous pregnancy, discuss the appropriate timing with your obstetrician.
When does the seventh month of pregnancy start on ultrasound?
The seventh month of pregnancy is commonly considered to begin at approximately 28 weeks, marking the start of the third trimester. Month-by-month calculations are approximate because calendar months do not contain exactly four weeks.
Around this stage, your doctor may recommend a growth scan to assess the baby’s size, estimated weight, position, amniotic fluid and placental location.
An obstetric Doppler study may also be advised if there is a clinical reason to assess blood flow.
Not every pregnancy requires a scan exactly at 28 weeks. The timing should follow your obstetrician’s recommendation and the purpose of the examination.
What scan shows whether the baby is a boy or a girl?
Ultrasound can sometimes visualise external genital anatomy during pregnancy, but fetal sex determination is not the purpose of routine antenatal screening.
In India, prenatal sex determination and disclosure of fetal sex before birth are prohibited under the Pre-Conception and Pre-Natal Diagnostic Techniques (Prohibition of Sex Selection) Act, commonly called the PCPNDT Act.
Healthcare providers must comply with these legal requirements. Pregnancy ultrasound examinations should focus on the baby’s health, development and any clinically relevant findings.
How to prepare for a pregnancy ultrasound
Preparation depends on the type of scan and the stage of pregnancy.
Before your appointment:
- Follow the instructions provided by the diagnostic centre.
- Ask whether you need a full bladder, particularly for certain early abdominal scans.
- Bring previous ultrasound reports, blood test results and relevant medical records.
- Know the first day of your last menstrual period, if possible.
- Inform the healthcare professional about relevant symptoms and medical conditions.
- Allow sufficient time for the examination, as some scans may take longer if the baby’s position makes visualisation difficult.
Most routine pregnancy ultrasound examinations are painless. You may feel slight pressure from the transducer or mild discomfort from a full bladder.
The sonographer may need to change the probe angle or ask you to change position to obtain clearer images.
Are pregnancy ultrasonography tests safe?
Diagnostic ultrasound is widely used during pregnancy and has no known harmful effects when performed appropriately by trained professionals.
It does not use ionising radiation. Nevertheless, ultrasound should be performed for a medical purpose, using appropriate settings and exposure times.
Avoid unnecessary scans performed solely for keepsake videos or non-medical entertainment. If you have concerns about the safety, frequency or timing of your examinations, discuss them with your obstetrician.
What happens after the ultrasound?
After the examination, the images and measurements are reviewed and interpreted by an appropriately qualified medical professional.
The report may describe gestational age, fetal measurements, heartbeat when assessable, placental position, amniotic fluid and any relevant findings specific to the scan.
A normal report is reassuring, but it cannot rule out every possible fetal condition. Similarly, a finding that needs further evaluation does not always mean that a serious problem is present.
Your doctor may recommend a repeat ultrasound, a specialised examination, blood tests or referral for further assessment, depending on the findings.
Always review your scan report with your treating doctor, who can explain what the results mean for your individual pregnancy.
Pregnancy ultrasound scans at Sparsh Diagnostic Centre, Kolkata
Choosing the right pregnancy ultrasound at the appropriate time helps your doctor monitor fetal development and make informed decisions about antenatal care.
At Sparsh Diagnostic Centre, Kolkata, pregnancy ultrasonography services can help expectant parents access imaging examinations recommended during different stages of pregnancy, subject to the availability of the specific scan and clinical requirements.
Whether you have been advised to undergo an early pregnancy scan, NT scan, anomaly scan, fetal echocardiography, growth scan or obstetric Doppler examination, follow your doctor’s instructions regarding timing and preparation.
For information about available pregnancy ultrasound examinations, appointment scheduling and preparation requirements, contact Sparsh Diagnostic Centre before visiting.
Your pregnancy scan is an important part of your care, but it works best when combined with regular antenatal check-ups, appropriate screening tests and guidance from your obstetrician.
Frequently asked questions about pregnancy ultrasonography tests
1. How many ultrasound scans are required during pregnancy?
There is no fixed number for every pregnancy. Many women have a first-trimester assessment and an anomaly scan, while some also require a third-trimester growth scan. Additional scans depend on medical needs and the advice of the treating doctor.
2. Which ultrasound is best for early pregnancy?
A transvaginal ultrasound often provides clearer images during very early pregnancy. Your doctor may recommend it to assess pregnancy location, early development and gestational age.
3. Can an ultrasound confirm pregnancy 100%?
No test should be described as 100% accurate in every circumstance. A urine or blood hCG test can detect pregnancy, while ultrasound helps assess its location and development. Very early scans may be inconclusive, so follow-up testing may be needed.
4. Can a pregnancy be detected at two weeks?
A two-week pregnancy, calculated from the last menstrual period, is generally too early to visualise reliably on ultrasound. Pregnancy testing with urine or blood hCG is usually more useful.
5. When should the first pregnancy scan be done?
An early scan may be performed around 6–8 weeks when clinically indicated. In other cases, the first planned scan may occur around 11–14 weeks. Your doctor will recommend the most suitable timing.
6. What is the difference between an NT scan and an anomaly scan?
An NT scan is generally performed during the late first trimester and measures the fluid space behind the baby’s neck as part of screening for certain conditions. An anomaly scan is usually performed around 18–22 weeks to examine the baby’s developing anatomy in greater detail.
7. Is a Doppler scan necessary for every pregnancy?
No. Doppler ultrasound is recommended when the doctor needs information about blood flow, particularly in certain high-risk pregnancies or when fetal growth or placental function is a concern.
8. When does the seventh month of pregnancy begin?
The seventh month is commonly considered to begin around 28 weeks, at the start of the third trimester. A growth scan may be recommended around this period or later, depending on your doctor’s advice.
9. Can an ultrasound detect fetal abnormalities?
Ultrasound can identify many structural abnormalities, particularly during a detailed anomaly scan. However, not every abnormality can be detected, and some findings require additional investigations.
10. Is pregnancy ultrasound painful or harmful?
Most routine pregnancy scans are painless and are considered safe when performed appropriately by trained professionals. A transvaginal scan may cause temporary discomfort.
11. Do I need a full bladder for a pregnancy ultrasound?
It depends on the scan. Some early abdominal scans may require a full bladder, while other examinations do not. Follow the preparation instructions given by your diagnostic centre.
12. Can I have an ultrasound without a doctor’s advice?
The appropriate scan depends on your gestational age, symptoms and medical history. It is best to consult your obstetrician or healthcare provider to determine whether an examination is necessary and which type is suitable.
13. Can ultrasound determine the baby’s sex in India?
Prenatal sex determination and disclosure of fetal sex are prohibited under Indian law. Pregnancy ultrasound should be used for legitimate medical assessment of fetal development and maternal health.
14. Does a normal ultrasound guarantee a healthy baby?
No. A normal scan is reassuring but cannot exclude every genetic, structural or developmental condition. Continue routine antenatal care and complete other screening tests recommended by your doctor.
15. How long does a pregnancy ultrasound take?
The duration varies with the type of examination and the quality of images obtained. Many routine scans take approximately 20–30 minutes, although specialised examinations may take longer.
Pregnancy ultrasonography tests provide valuable information about the location, growth and development of the baby throughout pregnancy. From early pregnancy and dating scans to anomaly scans, fetal echocardiography and third-trimester growth assessments, each examination serves a specific purpose.
The number and timing of scans should be tailored to your pregnancy rather than determined by a rigid schedule. If you have questions about which pregnancy USG test you need, speak to your obstetrician and follow the recommended antenatal screening plan.
Sparsh Diagnostic Centre, Kolkata, encourages expectant parents to seek appropriate medical guidance, attend scheduled examinations and discuss their ultrasound reports with their treating doctor.
If you still have questions or need to consult a Gynecologist, call our helpline numbers +91 98301 17733 and +91 83350 49501.
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Disclaimer:
No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.
Sources and further reading
The following authoritative medical resources provide additional information about pregnancy ultrasonography, pregnancy testing, scan timing and safety.
- Cleveland Clinic. Ultrasound in Pregnancy: What to Expect, Schedule and Results.
https://my.clevelandclinic.org/health/diagnostics/9704-ultrasound-in-pregnancy - Better Health Channel, Victoria State Government. Pregnancy tests and ultrasound.
- MedlinePlus, U.S. National Library of Medicine. Ultrasound.
https://medlineplus.gov/lab-tests/sonogram/ - MedlinePlus, U.S. National Library of Medicine. Pregnancy Test.
https://www.medlineplus.gov/lab-tests/pregnancy-test/ - American College of Obstetricians and Gynecologists (ACOG). Ultrasound Exams.
https://www.acog.org/womens-health/faqs/ultrasound-exams - National Health Service (NHS), United Kingdom. Ultrasound scans in pregnancy.
https://www.nhs.uk/pregnancy/your-pregnancy-care/ultrasound-scans/ - International Society of Ultrasound in Obstetrics and Gynecology (ISUOG). Ultrasound in pregnancy.
- World Health Organization (WHO). Recommendations on antenatal care for a positive pregnancy experience.
- Government of India. Pre-Conception and Pre-Natal Diagnostic Techniques (Prohibition of Sex Selection) Act, 1994, as amended.
Medical review
This article has been medically reviewed by Dr. Shubhayu Som to support the accuracy and reliability of the information presented.
Medical reviewer: Dr. Shubhayu Som
Qualification: MBBS
Specialisation: General Physician
Medical registration: West Bengal Medical Council
WBMC registration number: 81060
Date medically reviewed: 29th October 2026
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