Pregnancy Ultrasound Scan Schedule: A Trimester-by-Trimester Guide

Medically reviewed by Dr. Priyadatt Patel, MBBS, MS (Obstetrics & Gynaecology) — Senior Gynecologist · Advanced Laparoscopic Surgeon · IVF and Endometriosis Programme Lead, Fetal Medicine & Advanced Ultrasound, Balaji Horizon Women’s Hospital, Ahmedabad.  ·  Last reviewed: 26 June 2026.

Ultrasound is one of the most reassuring parts of antenatal care, and one of the most misunderstood. Expectant parents often ask the same practical questions: How many scans do I really need? When is each one done? What does it check? This guide answers those questions by walking through the recommended scan schedule trimester by trimester, in line with ISUOG and NICE guidance. It also explains a principle we hold firmly at Balaji Horizon: the goal is the right scan at the right time, not the largest number of scans. For the wider picture, see our pregnancy care overview and our fetal-medicine scans hub.

Pregnancy scan schedule at a glance

The table below is a quick reference. The sections that follow explain each scan in detail. Exact timing is always individualised by your obstetrician, and dates are counted from the first day of your last menstrual period (or corrected by an early scan).

How many ultrasound scans do you need in pregnancy?

For an uncomplicated pregnancy, NICE recommends two routine scans: a dating scan (offered between 11⁺² and 14⁺¹ weeks) and an anomaly scan (offered between 18⁺⁰ and 20⁺⁶ weeks). Every additional scan should answer a specific clinical question rather than be done automatically.

In Indian practice, an early dating/viability scan and a third-trimester growth or wellbeing scan are also commonly performed. Used thoughtfully these are reasonable, but they should be individualised, for example, an early scan after bleeding or an IVF conception, or a growth scan when there is a reason to watch the baby’s size closely. More scans are not automatically safer or more reassuring; the value lies in performing the correct scan at the correct gestational window.

First trimester: the dating & viability scan (6–11 weeks)

The earliest scan confirms an intrauterine pregnancy with a heartbeat, establishes how many babies there are (and, in twins, the all-important chorionicity), and sets accurate dates. Crown–rump length measured between 11⁺⁰ and 13⁺⁶ weeks (CRL 45–84 mm) is the most accurate way to date a pregnancy, which is why early dating matters for everything that follows. A very early scan at 6–8 weeks is usually performed to confirm viability and location, for instance after pain, bleeding, or assisted conception. Read more on our dating & viability scan page.

First trimester: the NT scan, combined screening & NIPT (11⁺⁰–13⁺⁶ weeks)

The nuchal translucency (NT) scan measures the small pocket of fluid behind the baby’s neck. Combined with maternal age and two blood markers (PAPP-A and free β-hCG), it estimates the risk of Down syndrome (trisomy 21), Edwards syndrome (trisomy 18) and Patau syndrome (trisomy 13), and gives an early look at major anatomy. The scan window is the same as for accurate dating: 11⁺⁰ to 13⁺⁶ weeks. Our NT scan page explains the measurement and how risk is calculated.

NIPT (non-invasive prenatal testing) is a separate, highly sensitive screening blood test that analyses cell-free fetal DNA from about 10 weeks. It is important to understand that NIPT is a screening test, not a diagnostic one: a high-risk result should be confirmed with a diagnostic test (chorionic villus sampling or amniocentesis) before any decision is made. In India, NIPT — like every other prenatal test, is governed by the law described below and is never used to reveal the baby’s sex.

Second trimester: the TIFFA / anomaly scan (18–22 weeks)

The mid-trimester scan, often called TIFFA (Targeted Imaging for Fetal Anomalies) or simply the anomaly scan, is the most detailed examination of your baby’s anatomy. Performed between 18 and 22 weeks (NICE offers it at 18⁺⁰–20⁺⁶ weeks), the sonologist systematically checks the brain and spine, face and lips, heart, chest, abdominal organs, kidneys and bladder, limbs, and the placenta and amniotic fluid, following the standardised ISUOG protocol.

In experienced hands the anomaly scan detects most major structural abnormalities, but it is honest and important to know that no scan can detect every condition, and some problems only become apparent later in pregnancy. Because this scan deserves a full explanation of exactly what is examined and what findings mean, we have a dedicated guide: see our anomaly (TIFFA) scan page.

Second-trimester add-ons: fetal echocardiography & cervical length

Two targeted scans are offered when there is a specific reason. A fetal echocardiography is a detailed study of the baby’s heart, usually around 18–24 weeks, recommended when the risk of a heart defect is higher, for example pre-existing diabetes, a family history of congenital heart disease, or certain first-trimester findings. A cervical length measurement (often 16–24 weeks) helps identify women at higher risk of preterm birth, so that preventive steps can be considered in good time. Neither is universal; both are added on clinical grounds.

Third trimester: growth, Doppler & wellbeing scans (28–36 weeks)

A growth scan estimates the baby’s weight, measures the amniotic fluid, and checks the position of the placenta. Added to it, a Doppler study assesses blood flow in the umbilical artery and other vessels, a valuable window on how well the placenta is supporting the baby. These are especially important with high blood pressure, diabetes, a baby measuring small or large, reduced fetal movements, or a previous complicated pregnancy.

An honest, evidence-based note: for genuinely low-risk pregnancies, routine third-trimester scanning has not been clearly shown to improve outcomes (NICE), so it is best offered for a reason. Many Indian units perform a wellbeing scan around 32 weeks; this is reasonable when used thoughtfully and interpreted alongside the whole clinical picture, rather than as a routine that replaces clinical judgement.

Routine versus indicated scans: what the evidence supports

It helps to separate scans into two groups. Routine scans are offered to everyone: the dating scan and the anomaly scan. Indicated scans are added when there is a specific reason: an early viability scan, fetal echocardiography, cervical length, and serial growth or Doppler studies. This distinction reflects our broader philosophy of evidence-based, no-overtreatment care, each scan should answer a clear question and inform a decision, not simply add another image to the file.

3D and 4D scans: what they can and cannot show

3D and 4D imaging produce lifelike still pictures and moving video and can help visualise certain surface features such as facial clefts. They are an adjunct, however, not a replacement for the standard 2D anomaly scan, which remains the diagnostic gold standard. Image quality depends on the baby’s position, the amount of fluid and other factors, so it is wise to keep expectations realistic. Learn more on our 3D / 4D scan page.

Sex determination and the law in India (PCPNDT Act)

Under the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994, determining or disclosing the sex of a fetus before birth, by ultrasound or any other technique, is illegal in India. Ethical centres, including Balaji Horizon, never reveal fetal sex, and our ultrasound services are provided strictly for medical purposes. This law exists to protect against sex-selective practices, and we are committed to it both legally and ethically. Please understand that our team cannot and will not share this information.

How to prepare for your scan and what to expect

Preparation is simple. For very early scans a comfortably full bladder can help the view; later scans usually do not require this. Wear loose, comfortable clothing and bring your previous reports. The scan itself is painless and uses sound waves, not ionising radiation. Duration varies, a detailed anomaly scan can take 30–45 minutes, particularly if the baby is in an awkward position and needs time to move. You are always welcome to ask the sonologist questions about what is being examined.

When are extra scans recommended?

Additional scans are appropriate in several situations: a twin or higher-order pregnancy; a previous preterm birth or pregnancy loss; high blood pressure or pre-eclampsia; diabetes (pre-existing or gestational); a baby suspected to be growing too slowly or too fast; reduced fetal movements; bleeding; an abnormal screening result; or a pregnancy conceived through IVF or otherwise considered higher-risk. If your pregnancy needs closer monitoring, your obstetrician will explain which scans are advised and why, see our pregnancy and high-risk care services.

Frequently asked questions

References

1. National Institute for Health and Care Excellence. Antenatal care (NG201). 2021.
2. ISUOG Practice Guidelines (updated): performance of the 11–14-week ultrasound scan. Ultrasound Obstet Gynecol. 2023. doi:10.1002/uog.26106.
3. Salomon LJ, et al. ISUOG Practice Guidelines (updated): performance of the routine mid-trimester fetal ultrasound scan. Ultrasound Obstet Gynecol. 2022;59(6):840–856. doi:10.1002/uog.24888.
4. ISUOG Practice Guidelines: ultrasound assessment of fetal biometry and growth. Ultrasound Obstet Gynecol. 2019;53:715–723. doi:10.1002/uog.20272.
5. The Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994. Government of India.

This article is for general education and does not replace personalised medical advice. The timing and choice of scans should be individualised by your own obstetrician. If you have questions about your pregnancy or a scan finding, please consult a qualified specialist.

About the Author

Dr. Priyadatt Patel

Senior Gynecologist · Advanced Laparoscopic Surgeon · IVF & Endometriosis Programme Lead

Founder of Balaji Horizon Women’s Hospital. ESHRE / ASRM / FIGO-aligned practice. ★ 5.0 on Google · 287 reviews.

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