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Tests & Scans in Pregnancy: Dating Scan, 20-Week Scan, Screening & Blood Tests
Antenatal tests and scans are a routine, reassuring part of pregnancy care.
Quick Facts
Antenatal tests and scans are a routine, reassuring part of pregnancy care — they check your baby's growth and development and your own health, and offer information to help you make choices. Most are offered (not compulsory), and your midwife or doctor will explain each so you can decide what's right for you.
The two main ultrasound scans are the dating scan (around 11–14 weeks), which confirms your due date and number of babies, and the 20-week anomaly scan (usually 18–21 weeks), which checks your baby's development and growth. You'll also be offered screening for conditions like Down's, Edwards' and Patau's syndromes, and routine blood tests at booking and again around 28 weeks.
This guide explains each test and scan — what it is, when it happens, and what it checks — so the schedule feels clear rather than confusing. Screening is always your choice.
Stay organised
Keep all your scan reports and results together, and track appointment dates as you go — it makes each appointment easier and helps you spot what's coming next.
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Things worth knowing
The dating scan sets your due date
Around 11–14 weeks it confirms your due date and how many babies you're expecting.
The 20-week scan checks development
Usually 18–21 weeks, it looks at your baby's physical growth, the placenta and around 11 conditions.
Blood tests protect you both
At booking and ~28 weeks they check blood group, anaemia, infections and antibodies.
Screening is not diagnosis
It estimates the chance of a condition — it doesn't give a yes or no answer.
Tests are offered, not required
They're a choice; your midwife or doctor explains each so you can decide.
Stay organised for each visit
Keeping reports and dates together makes appointments easier and shows what's next.
Everything You Need to Know (The Main Tests & Scans)
Here are the main antenatal tests and scans you may be offered, when they happen, and what each one checks:
| Test / scan | When | What it checks |
|---|---|---|
| Booking bloods | Before ~11 weeks | Blood group, anaemia, infections (e.g. HIV, hepatitis B, syphilis), immunity |
| Dating scan | ~11–14 weeks | Confirms due date and number of babies; the scan date is used throughout |
| Combined screening | ~11–14 weeks | Down's/Edwards'/Patau's risk — nuchal-translucency ultrasound + blood test |
| Quadruple (quad) test | 14–20 weeks | Alternative blood screen for Down's if past 14 weeks |
| 20-week anomaly scan | 18–21 weeks | Baby's physical development (checks for ~11 conditions), growth, placenta |
| 28-week bloods | ~28 weeks | Repeat anaemia/antibody checks; anti-D if Rh-negative |
| Later checks | Ongoing | Blood pressure, urine, growth, position, movements |
Screening is a choice
Screening estimates the chance of a condition; it doesn't diagnose. If a screen shows higher chance, you may be offered further (diagnostic) tests — your team will explain options and support your decision.
Why & When Tests Are Done
You don't need symptoms — these are routine. Extra tests may be offered if:
Reasons extra tests may be offered
- You have a health condition (e.g. diabetes, high blood pressure)
- There are growth or movement concerns
- Screening shows a higher chance result
- You have a multiple pregnancy or other risk factors
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Tick the symptoms that apply to you. This is a self-check, not a diagnosis — saved on this device only.
Purpose of Each Test
Why each is offered:
- Dating scan
- Accurate due date and detecting multiples.
- Screening
- Information about the chance of certain conditions, to support informed choices.
- Anomaly scan
- Checking physical development and growth.
- Blood tests
- Protecting you and baby (anaemia, infections, blood-group/antibody issues).
- Ongoing checks
- Catching issues like high blood pressure or growth concerns early.
Screening vs Diagnostic Tests
An important distinction:
How the tests differ
- Screening tests estimate the chance of a condition (e.g. combined/quad test, anomaly scan). They don't give a yes/no.
- Diagnostic tests (e.g. amniocentesis or CVS) can confirm a condition but carry a small risk; they're offered only when indicated, with counselling.
- You choose whether to have screening and any follow-up — your team supports you either way.
After the Results
Results guide care and choices:
- Reassuring
- Routine care continues.
- Higher-chance screen
- Offer of further information and diagnostic tests; specialist/counselling support.
- Growth/BP/urine concern
- More frequent monitoring; specialist referral if needed.
- Blood-test finding
- Specific treatment (e.g. iron for anaemia, anti-D for Rh-negative).
Prepare your questions
Decisions after results are personal — your midwife, doctor and (if needed) specialist counsellors are there to support you without pressure. The ParentVibes Ask a Doctor feature can help you prepare questions for these conversations.
Ask a Doctor →Preparing for Tests & Scans
Before your appointment
- Know the schedule and attend appointments
- Ask questions beforehand about what each checks and your choices
- Follow any prep (e.g. some scans suggest a comfortably full bladder — your clinic will advise)
- Bring support if you'd like someone with you
- Look after your wellbeing — waiting for results can be anxious; lean on support
Tests & scans checklist
- Dates noted
- Prep instructions followed
- Questions ready
- Previous results to hand
- Support arranged
When to See a Doctor
Contact your midwife/maternity unit promptly for:
- Bleeding, severe pain, or fluid leaking
- Reduced/changed movements (later pregnancy)
- Pre-eclampsia signs (severe headache, vision changes, sudden swelling)
- Concerns about a result or what it means
- Missing or needing to reschedule an important scan/test
Seek urgent care
Seek urgent care for bleeding, severe pain, reduced movements, or pre-eclampsia signs (severe headache, vision changes, sudden swelling).
Continue learning
Frequently Asked Questions
What scans will I have?
Usually a dating scan (~11–14 weeks) and a 20-week anomaly scan (18–21 weeks), plus screening tests and routine bloods.
Are tests and scans compulsory?
No — they're offered, and you choose. Your team explains each so you can decide.
What's the difference between screening and diagnostic tests?
Screening estimates the chance of a condition; diagnostic tests (like amniocentesis) can confirm but carry a small risk.
What does the dating scan do?
Confirms your due date and how many babies you're expecting; the scan date is used through your pregnancy.
What does the 20-week scan check?
Your baby's physical development (looking for around 11 conditions), growth, and the placenta.
What blood tests will I have?
At booking and ~28 weeks — checking blood group, anaemia, infections and antibodies.
Will I find out the baby's sex at the 20-week scan?
The scan's main purpose is checking your baby's health, not determining sex. In India, prenatal sex determination is prohibited by law (PCPNDT Act), so clinics will not disclose the baby's sex.
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Medical review
- Last reviewed
- June 2026
- Medical reviewer
- Dr. Vinika G.
- Next review due
- June 2027
- Status
- Medically reviewed by Dr. Vinika G.
References
This article is for general information and education only and is not a substitute for professional antenatal care. Tests and screening are offered as choices; your midwife or doctor will explain options for your situation. In a medical emergency, contact your maternity unit or local emergency services immediately. In India, prenatal sex determination is prohibited by law (PCPNDT Act). Content reviewed against guidance from the NHS.
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Medical disclaimer
This article is for educational purposes only and does not replace medical advice. If you have severe pain, heavy bleeding, missed periods, or unusual symptoms, please consult a qualified healthcare provider.