What tests and scans happen in the second trimester?
In short
- In the second trimester, most people have the anomaly scan, a detailed check of your baby's body.
- This is also when the diabetes test usually happens, and a quad blood test may be offered.
- Each test tells your doctor something different — none of them replaces the others.
- Your antenatal card will show exactly which ones apply to you, and when.
What happens
- Around 18 to 22 weeks: the anomaly scan, a detailed ultrasound of your baby's body, organs and growth.
- Around 24 to 28 weeks in India's schedule: the GDM (gestational diabetes) blood-sugar test.
- Between 15 and 22 weeks, if applicable: the quad marker blood test, usually offered if first-trimester screening wasn't done.
Baby's sex is never revealed
It is illegal in India for anyone -- including your sonographer -- to reveal, or help you find out, the sex of your baby before birth. This is the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994.
Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994. Read the Act (India Code).
The details: numbers and where they differ
In the source's own words
The 20-week screening scan, also called the anomaly scan, is an ultrasound scan to look for 11 different conditions in your baby. It also checks your baby's growth. It's usually done when you're between 18 and 21 weeks pregnant.
NHS (UK), 20-week scan. Quoted verbatim.
Single step testing using 75 gm oral glucose & measuring blood sugar 2 hours after ingestion. ... The threshold blood sugar level of ≥140 mg/dL (more than or equal to 140) is taken as cut off for diagnosis of GDM.
Ministry of Health & Family Welfare, Govt of India (National Health Mission), Diagnosis & Management of Gestational Diabetes Mellitus — Technical and Operational Guidelines (2018). Quoted verbatim.
The numbers
| Measure | Value | Source |
|---|---|---|
| Anomaly scan window (pregnant women) | 18–21 (NHS) / 18–22 (ACOG) weeks gestation | NHS (UK) |
| 75g OGTT, 2-hour blood sugar (India's single-step test) (pregnant women, any trimester, fasting or non-fasting, India) | ≥140 mg/dL | Ministry of Health & Family Welfare, Govt of India (National Health Mission) |
| Quad marker screening window (pregnant women (ACOG, US)) | 15–22 weeks gestation | American College of Obstetricians and Gynecologists (ACOG) |
When to call your doctor
- If you're not sure which of these tests you've been offered or when they're scheduled for you.
- If any result comes back needing follow-up and you're unclear on the next step.
Discuss your results with your doctor: this page reports what these sources say, not advice for your situation.
Sources
- NHS (UK), 20-week scan. Quoted verbatim. OGL-style NHS content, free reuse with attribution.
- Ministry of Health & Family Welfare, Govt of India (National Health Mission), Diagnosis & Management of Gestational Diabetes Mellitus — Technical and Operational Guidelines (2018), 2018. Quoted verbatim. © Govt of India; page 4 grants free reproduction/quotation with attribution.
- American College of Obstetricians and Gynecologists (ACOG), Prenatal Genetic Screening Tests (Patient FAQ). Named as the guideline this section describes; its text and tables are not reproduced here (All rights reserved (cite only)). Describes the quad test's 15-to-22-week window and the conditions it screens for.
Sources checked 2026-09-26. How we source and check every page.
Educational summary of named sources, not medical advice.