Prenatal Tests and Scans, Week by Week

Fetal development at week 12 — the week of the first routine scan

Pregnancy comes with a schedule nobody hands you in one piece. You get a date for a booking appointment, then a letter about a scan, then a form about blood tests, and somewhere around 24 weeks a drink of glucose you were not expecting. Each piece arrives on its own, which makes the whole thing feel more improvised than it is.

It is not improvised. The antenatal timetable is a sequence of checks, each placed at the week it works best, and most of them are looking for something specific and treatable. This page lays the whole sequence out in order — which week, which test, what it is actually looking for, and which results mean another appointment rather than bad news.

The short answer: a routine pregnancy in the UK includes at least 10 antenatal appointments for a first baby (7 if you have given birth before) and two ultrasound scans — one between 11 and 14 weeks and the anomaly scan between 18 and 21 weeks. Blood tests are taken at booking, around 28 weeks, and at any point a symptom calls for them. A glucose tolerance test is offered between 24 and 28 weeks to anyone with a risk factor for gestational diabetes. Every appointment, without exception, includes a blood pressure reading and a urine test.

The whole schedule on one page

Week ranges below follow the NHS antenatal pathway, which is the most explicitly published of the national schedules. Your own dates will shift by a week or two around them, and a country with a different programme will differ more; the sequence and the reasoning behind it are the same nearly everywhere.

For the international floor rather than one country's version, the WHO's 2016 model recommends a minimum of eight antenatal contacts — the first within the first 12 weeks, then at 20, 26, 30, 34, 36, 38 and 40 weeks. That replaced a four-visit minimum, and the change was made because eight contacts reduce perinatal deaths by up to 8 per 1,000 births compared with four.

WeekAppointmentWhat happens
8–12 Booking appointment The long one, around an hour. History, height and weight, blood pressure, urine, and the first round of blood tests. Screening is explained and you decide what to accept.
Before 10 Sickle cell and thalassaemia screening A blood test, ideally done before 10 weeks so there is time to test the baby's father if yours is positive.
11–14 First scan + combined screening Dates the pregnancy, counts the babies, checks the heartbeat. With a blood sample it becomes the combined test for Down's, Edwards' and Patau's syndromes.
14–20 Quadruple test Only offered if the combined test could not be done in time — a blood test that screens for Down's syndrome alone.
16 Midwife appointment Blood pressure, urine, and the results of the booking bloods and first-trimester screening are discussed.
16–32 Whooping cough vaccine Usually given at 20 weeks, available from 16. Antibodies cross the placenta and protect the baby for the first weeks of life.
18–21 Anomaly scan The detailed one. The baby's brain, heart, spine, kidneys, limbs and abdomen are examined, and the placenta's position is checked.
24 Fundal height measured from here Your bump is measured with a tape from the pubic bone and plotted on a growth chart at every subsequent visit.
24–28 Glucose tolerance test Offered if you have a risk factor for gestational diabetes. Fasting blood sample, a glucose drink, a second sample two hours later.
25 Midwife appointment First baby only. Blood pressure, urine, fundal height.
28 Second round of bloods + anti-D Full blood count for anaemia and antibody screening. If you are RhD negative, anti-D immunoglobulin is offered from 28 weeks.
31 Midwife appointment First baby only. The usual checks plus results from the 28-week bloods.
34 Midwife appointment The usual checks, plus the conversation about labour, pain relief and your birth preferences.
36 Position check The baby's position is felt for. If the baby is breech, a scan confirms it and turning the baby is discussed.
38, 40, 41 Late appointments The usual checks. At 41 weeks, induction is discussed and a membrane sweep is usually offered.

If you want the version with what to ask at each one, our guide to the antenatal appointment schedule goes visit by visit. To see where you are in the sequence right now, the due date calculator converts a date into a gestational week, and the week-by-week guide covers what is happening at each of them.

Screening or diagnosis? The distinction that matters most

Almost every test offered routinely in pregnancy is a screening test, and screening does something narrower than most people expect. It estimates a probability. It sorts pregnancies into a higher-chance group and a lower-chance group, and it is wrong in both directions a predictable proportion of the time.

A diagnostic test answers the question outright, because it samples the pregnancy itself — placental tissue in a chorionic villus sampling, amniotic fluid in an amniocentesis. That certainty costs something: both are invasive procedures carrying a small risk of miscarriage, so neither is offered out of curiosity.

"Higher chance" is not a diagnosis. A screening result of 1 in 150 means 149 out of 150 pregnancies with that result do not have the condition. It is a reason to be offered a further test, and it is the point at which you should be given time, written information and a conversation with someone who does this every day — not a decision to make in the corridor.

What happens at every single appointment

Underneath the tests that vary by week, three checks repeat at every visit, and they exist to catch the complications that develop quietly.

🩺 The three constants

From around 24 weeks you will also be asked about your baby's movements at every appointment. That question is not small talk — a change in the pattern is one of the few warnings a baby can give, and our guide to kick counts and baby movements covers what to watch for between visits.

The blood tests, and what they are looking for

The booking bloods look like a lot of vials for one appointment. They are testing for several unrelated things at once, all of which are easier to manage the earlier they are found.

Read the one that applies to you

Each of these goes deeper than a row in a table can: what the test measures, what the numbers on the report mean, and what happens if a result comes back outside the expected range.

Weeks 8–41 The antenatal appointment schedule Every visit in order, what happens at each one, and what to ask. Weeks 6–10 Early pregnancy ultrasound What an early scan can and cannot show, and when one is offered. Weeks 11–14 First trimester screening The nuchal translucency scan and blood test, and how the risk figure is worked out. From week 10 NIPT and cell-free DNA testing What NIPT screens for, how accurate it really is, and when a diagnostic test follows. Weeks 18–21 The 20-week anomaly scan The eleven conditions it looks for, and what a soft marker means. Any scan Ultrasound results explained BPD, HC, AC, FL, EFW and AFI — every abbreviation on the report. Weeks 14–40 Fetal growth percentiles What P5, P50 and P95 mean, and when a small measurement is a concern. Weeks 8–28 Blood tests in pregnancy Every blood test by trimester, what it screens for and what the result means. Weeks 24–28 The glucose tolerance test How the OGTT works, the diagnostic thresholds, and how to prepare for it. Every visit Blood pressure and pre-eclampsia Normal ranges, what counts as high, and the pre-eclampsia warning signs.

Getting more out of an appointment

Antenatal appointments are short, and the useful ones are usually the ones you arrived at prepared for. Three things make a measurable difference:

Write the questions down before you go. Every midwife has had the conversation where the important question surfaces as the patient is putting their coat on. A note on your phone costs nothing and changes what gets covered.

Bring your own numbers. If you have been taking your blood pressure at home, or tracking symptoms, or you have a scan report from a private clinic, bring the record rather than the recollection. A series of readings tells a midwife something a single measurement cannot.

Ask what a result means for the next appointment. "Is this being rechecked, and when?" turns an ambiguous number into a plan. Most borderline results in pregnancy are managed by repeating the test, and knowing that in advance removes most of the worry attached to the word "borderline".

When not to wait for the next appointment

Call your midwife or maternity unit the same day if: you have vaginal bleeding, a gush or steady trickle of fluid, severe or one-sided abdominal pain, a severe headache with visual disturbance or sudden swelling of the face and hands, a fever, or — after 24 weeks — if your baby's movements have slowed or changed. Do not wait for a scheduled appointment and do not wait until morning.

The schedule on this page is designed for a pregnancy that is going normally. It has deliberate gaps — four weeks between appointments in the second trimester — and those gaps assume you will ring if something changes. Maternity units are staffed around the clock precisely for this, and nobody there considers a call that turns out to be nothing a waste of their time.

Frequently Asked Questions

How many scans do you get during pregnancy?

In the UK, two are offered routinely: a scan between 11 and 14 weeks and the anomaly scan between 18 and 21 weeks. More are arranged when there is a reason — twins, a low-lying placenta, bleeding, a growth concern, or a previous complication. Private clinics sell additional scans, but extra images do not improve outcomes in an uncomplicated pregnancy and are not part of any national programme.

How many antenatal appointments will I have?

The NHS offers at least 10 appointments if this is your first baby and at least 7 if you have given birth before. The traditional US schedule runs to 12–14 visits, though ACOG's 2025 clinical consensus moved away from a fixed number and towards a schedule matched to each pregnancy. Either way, appointments cluster towards the end: fortnightly from 28 weeks, weekly from 36.

What is the difference between a screening test and a diagnostic test?

A screening test estimates a probability. It sorts pregnancies into higher and lower chance and can be wrong in both directions, so a "higher chance" result is not a diagnosis. A diagnostic test — CVS or amniocentesis — samples the pregnancy itself and gives a definite answer, at the cost of a small procedure-related miscarriage risk. Almost everything offered routinely is screening.

Which prenatal tests are compulsory?

None of them. Every antenatal test is offered, not imposed, and you can accept some and decline others — most people accept the infection screening and the scans while thinking harder about chromosomal screening. Declining a test is recorded and does not affect the rest of your care. What is worth avoiding is deciding by default: a test you did not think about is harder to interpret when the result arrives.

What happens at every antenatal appointment?

Blood pressure and a urine dip at all of them, because together they are the main screen for pre-eclampsia. From 24 weeks your bump is measured from the pubic bone to the top of the uterus and plotted on a growth chart. From around 24 weeks you will be asked about the baby's movements at each visit, and later in pregnancy the baby's position is checked by hand.

When is the glucose tolerance test done?

Between 24 and 28 weeks, which is when placental hormones peak and gestational diabetes becomes detectable. If you have had gestational diabetes before, testing is usually offered much earlier — often soon after booking — and repeated at 24–28 weeks if the first result was normal.

Can I bring someone to my scans?

Usually yes, though hospitals set their own limits on how many people and whether children can come. The anomaly scan is a detailed clinical examination and the sonographer will go quiet while concentrating, which is normal and not a signal that something is wrong. If you would rather not have company for that one, that is also a reasonable choice.

What should I take to an antenatal appointment?

Your maternity notes or app, a urine sample if your clinic asks for one, a list of your current medicines and supplements, and the questions you thought of at 3am and will otherwise forget. If you monitor your blood pressure at home, bring the readings — a record over several weeks is far more useful to a midwife than one number taken in a waiting room.

Prenatal tests and scans — at a glance

A routine pregnancy involves around ten appointments, two scans and three or four rounds of blood tests, spread across nine months and clustered towards the end. The first scan between 11 and 14 weeks confirms dates and, with a blood sample, becomes the combined screening test. The anomaly scan between 18 and 21 weeks examines the baby's anatomy in detail. Booking bloods cover blood group, anaemia and three infections that are treatable in pregnancy, and they are repeated at 28 weeks. A glucose tolerance test at 24–28 weeks looks for gestational diabetes. Underneath all of it, blood pressure and urine are checked at every visit, because pre-eclampsia gives almost no warning of its own. Everything is offered rather than required, and almost everything is screening rather than diagnosis.

Inside Baby Novum: the calendar marks ultrasound appointments, doctor's visits and lab tests with push reminders, the ultrasound log stores each scan's measurements and a photo of the report and plots them against WHO and INTERGROWTH-21st percentile bands, and the blood pressure and lab result journals keep the series a midwife actually wants to see. Everything stays on your phone — there is no account and no server.

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Keep every scan and result in one place

Baby Novum logs each ultrasound with its date, gestational week, measurements and a photo of the report, plots growth against WHO percentile bands, stores lab results and blood pressure readings, and reminds you before the next appointment.

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