Pregnancy Scans, Tests & Antenatal Care Explained
Every NHS scan and test from booking appointment to birth — what happens, what it measures, what the results mean, and what your options are at each decision point.
🌿 Open full lesson in WiseMama — free, with quizzes & flashcardsYour NHS Antenatal Schedule
The NHS offers a structured programme of antenatal care throughout your pregnancy. For a first pregnancy, you can expect around ten appointments; for subsequent pregnancies, approximately seven. Each appointment has a specific purpose, and understanding what each one involves ahead of time makes the experience considerably less stressful.
The Booking Appointment (Weeks 8–10)
Your booking appointment is the most comprehensive in the whole pregnancy, and it is worth treating it that way. Typically lasting 60–90 minutes with your community midwife, it covers far more ground than a standard clinical check.
Your midwife will take a full personal and family medical history, check your blood pressure and BMI, test your urine for infection, protein, and glucose, and carry out mental health screening. There will also be a private conversation about your home situation — domestic abuse screening is a routine and confidential part of every booking appointment.
The blood tests taken at booking are extensive: blood group and rhesus factor, full blood count (checking for anaemia), and infectious disease screening covering HIV, hepatitis B, hepatitis C, syphilis, and rubella immunity. Sickle cell and thalassaemia screening is also offered to everyone, with more detailed testing depending on family origin.
At this appointment you will also complete your maternity exemption certificate (MatEx), which entitles you to free prescriptions and NHS dental treatment throughout your pregnancy and for twelve months after birth.
The Dating Scan (Weeks 11–14)
Your first ultrasound serves two distinct purposes: it establishes exactly how many weeks pregnant you are, and it forms part of first trimester screening for chromosomal conditions.
The gestational age is calculated from the crown-to-rump length — the measurement from the top of the baby's head to the base of the spine. This gives a more accurate due date than the LMP calculation alone. The scan also checks the uterine structure, confirms the number of embryos, and verifies a fetal heartbeat.
The nuchal translucency (NT) measurement captures the fluid at the back of the baby's neck. A larger measurement is associated with, but does not confirm, chromosomal conditions. This NT value is combined with blood test results — PAPP-A and hCG — and your age to produce a combined risk ratio for Down's syndrome (trisomy 21), Edwards' syndrome (trisomy 18), and Patau's syndrome (trisomy 13).
I declined the combined screening at 12 weeks because I felt sure I wouldn't terminate. A week after the scan I was wracked with anxiety because I didn't actually know anything about my baby's health. I'd recommend doing the test and making the termination decision only if you face it — the information itself has value.
You do not have to have combined screening. Think about what you would want to do with a high-risk result before you go in for the scan, rather than trying to process it for the first time in the room.
The 20-Week Anomaly Scan (Weeks 18–21)
The anomaly scan is the most thorough structural assessment of your pregnancy. It is a systematic survey of your baby's anatomy and takes around 30 minutes. The sonographer works through a checklist — brain, face, spine, heart (four chambers and both outflow tracts), abdominal wall, stomach, kidneys, bladder, all four limbs, placental position, umbilical cord, and amniotic fluid volume.
The 20-week scan is about 30 minutes of a stranger looking at your baby very seriously and saying almost nothing. Have questions written down because the sonographer won't narrate, and you won't think straight in the room. Ask for extra photos — they don't always offer them.
If the sonographer identifies something they want to assess more closely, you may be asked to wait for a second opinion, referred for specialist fetal medicine scanning, or called back for a follow-up. This does not mean a serious problem has been found. Many findings at the anomaly scan resolve on review. If this happens to you, ask clearly: what exactly has been identified, how significant is it at this stage, what are the next steps, and what is the range of possible outcomes. You are entitled to clear answers.
Gestational Diabetes: The Glucose Tolerance Test
Gestational diabetes (GD) affects approximately one in twenty pregnancies in the UK. It develops when the body cannot produce sufficient insulin to meet the increased demands of pregnancy, leading to elevated blood glucose. With the right management, most pregnancies affected by GD have excellent outcomes.
The glucose tolerance test (GTT) is offered at around weeks 24–28 to people with specific risk factors: a BMI over 30, a previous baby weighing more than 4.5kg, a family history of type 2 diabetes in a first-degree relative, a personal history of GD, or a family origin from South Asia, East Asia, the Middle East, or Africa.
The test itself involves an overnight fast, a fasting blood glucose measurement, drinking a 75g glucose solution, and a second blood glucose measurement two hours later. It takes around two and a half hours in total. Bring a book or something to watch.
A GD diagnosis leads to specialist clinic input, dietary guidance, home blood glucose monitoring, and sometimes medication (metformin or insulin). GD almost always resolves after birth, though it does increase your lifetime risk of developing type 2 diabetes.
My GD diagnosis felt like a failure at first. Once I got into the diet and monitoring routine, it actually made me feel more in control, not less. The community on the gestational diabetes support forums is incredible — women sharing meal ideas, finger prick hacks, and exactly the right amount of dark humour.
Additional Tests and Referrals You May Be Offered
Beyond the standard schedule, a range of additional tests and referrals may be offered depending on your individual circumstances.
- Growth scans — arranged if fundal height measurements are small or large for dates, or if you have known risk factors for growth restriction or a large baby
- NIPT (non-invasive prenatal testing) — a blood test analysing cell-free DNA from the placenta to screen for chromosomal conditions with high accuracy. Available on the NHS in some areas following a high-risk combined screening result; privately from around week 10
- CVS (chorionic villus sampling) — a diagnostic test at weeks 11–14. Samples placental tissue via a fine needle. Provides chromosomal results with near-certainty. Carries approximately a 0.5–1% risk of miscarriage.
- Amniocentesis — diagnostic testing from week 15. Samples amniotic fluid. Slightly lower miscarriage risk than CVS at later gestations.
- Whooping cough vaccine — offered between weeks 16 and 32. Protects your newborn before they can be vaccinated themselves at 8 weeks. Strongly recommended.
- Cervical length scan — offered where there is a risk of preterm labour, based on history or symptoms.
Sonographers often step out to fetch a colleague for a second opinion on something they want a second set of eyes on, or because a particular structure was not clearly visible and they want guidance on positioning. Neither necessarily indicates a problem has been found. If you are concerned, ask directly: "Have you seen something worrying, or is this routine?" You are entitled to a clear explanation of what is happening at every point of your care.
In most NHS trusts, yes — but you need to ask before the scan begins. Sonographers do not volunteer sex information, as some families prefer not to know. The accuracy of sex determination at 20 weeks is around 98–99% when the baby is in a clear position. Some trusts do not offer sex determination at all — it is worth checking with your unit beforehand so you are not surprised.
Screening tests estimate your statistical risk of a condition but cannot confirm or rule it out — they produce a probability, not a yes or no answer. Diagnostic tests (CVS and amniocentesis) examine the baby's chromosomes directly and give a definitive result. Screening is offered first because it carries no procedural risk to the pregnancy. If screening identifies a high-risk result, diagnostic testing will be offered, which does carry a small risk of miscarriage. A high-risk screening result means a condition is possible — not that it is confirmed.
Group B Streptococcus is carried without symptoms by around 20–30% of people. If GBS is found in a vaginal or rectal swab, or in your urine, during pregnancy, you will be offered intravenous antibiotics during labour to protect your baby from early-onset GBS infection — which is rare but serious in newborns. Having GBS does not affect the type of birth you can have. Routine GBS testing is not currently part of standard NHS antenatal care in England, though it can be arranged privately if you prefer.