How an ultrasound scan works
An ultrasound machine sends high-frequency sound waves into the body through a hand-held probe. The waves bounce off organs and return to the probe, and a computer turns them into moving pictures on a screen. You cannot hear or feel the sound waves.
Ultrasound does not use X-rays or any other radiation. It has been used in pregnancy for decades and is considered safe for you and the baby when done for a medical reason by trained staff.
Types of scan used in women's health
The doctor chooses the type of scan based on what needs to be seen. Sometimes two types are done at the same visit.
| Type | How it is done | Often used for |
|---|---|---|
| Transabdominal | Probe moved over the lower abdomen with gel | Pregnancy scans, a general view of the pelvis |
| Transvaginal | Slim covered probe placed gently in the vagina | Early pregnancy, ovaries, lining of the womb |
| Doppler | Measures blood flow in vessels | Baby's growth concerns, ovarian cysts |
| Follicular study | Repeated scans across one cycle | Tracking egg release during fertility care |
A transvaginal scan gives a clearer picture of the womb and ovaries because the probe is closer to them. It is not usually offered to women who have never had vaginal intercourse. You can always ask for a female attendant to be present, and you can decline an internal scan.
Why a scan may be advised
If you are not pregnant
A pelvic scan helps your doctor look for the cause of symptoms such as:
- Heavy, painful or irregular periods
- Pelvic pain or a feeling of pressure in the lower abdomen
- Suspected fibroids, which may later need fibroid treatment
- Ovarian cysts or features linked to PCOS and PCOD
- Bleeding after menopause
- Checking the position of an intrauterine device
During pregnancy
Scans are a regular part of pregnancy care. The usual schedule is shown below, though your obstetrician may add or change scans depending on your health and the baby's growth.
| Scan | Usual timing | Main purpose |
|---|---|---|
| Dating and viability scan | First trimester | Confirms location, heartbeat and due date |
| NT scan | Around 11 to 14 weeks | Part of screening for chromosomal conditions |
| Anomaly scan | Around 18 to 20 weeks | Detailed check of the baby's organs |
| Growth scan | Third trimester, as advised | Baby's size, fluid and placenta |
The law on sex determination in India
Finding out or revealing the sex of an unborn baby is illegal in India under the PCPNDT Act. This applies to you, your family, the doctor and the scan centre. Every centre that performs pregnancy scans must be registered under the Act and must display a notice about this rule.
Before a pregnancy scan you will be asked to show identity proof and sign a declaration that you do not wish to know the baby's sex. Please do not ask the staff about it. They are not allowed to tell you by words, signs or any other means.
Your appointment
Getting ready
Preparation depends on the scan. For a transabdominal pelvic scan or an early pregnancy scan, you are often asked to drink water and arrive with a full bladder. For a transvaginal scan, you empty your bladder first. Wear loose two-piece clothing and carry your doctor's referral, earlier reports and identity proof. Fasting is not usually needed for a pelvic or pregnancy scan.
What happens in the scan room
- The staff check your referral and paperwork and explain which scan you will have.
- You lie on a couch and uncover your lower abdomen, or undress from the waist down for an internal scan.
- Gel is spread on your skin, or on the covered probe, to help the sound waves travel.
- The doctor moves the probe to view each organ and takes measurements. You may feel light pressure.
- The gel is wiped away and you can dress and use the washroom.
- The report is prepared, often on the same day, for you to take back to your gynecologist.
Most scans take 15 to 30 minutes. A detailed anomaly scan can take longer, especially if the baby is lying in an awkward position.
Understanding your report
The report lists measurements and describes what was seen. Terms such as endometrial thickness, follicle, cyst or fibroid are descriptions, not a final diagnosis. Many findings, like small simple ovarian cysts, are common and harmless.
Ultrasound also has limits. It cannot detect every condition, and picture quality depends on body build, the baby's position and the stage of pregnancy. A normal scan lowers the chance of a problem but cannot rule out everything. Let the doctor who ordered the scan explain the report in the light of your symptoms and other tests. Costs vary by city, centre and the type of scan.
When to see a gynecologist
Do not wait for a routine scan date if you notice any of these warning signs:
- Vaginal bleeding or severe abdominal pain in pregnancy
- Sharp one-sided pelvic pain with a missed period, dizziness or fainting
- The baby moving much less than usual in later pregnancy
- Any bleeding after menopause
- A swelling or lump in the lower abdomen, or bloating that does not settle
- Periods that are very heavy, very painful or have stopped without explanation
These symptoms need a doctor's examination first. The doctor then decides whether a scan, and which type, is required. This page offers general information and is not medical advice.
This page is general information for readers in India. It is not medical advice. Speak to a qualified gynecologist about your own health.