Prenatal Tests and Scans: What Happens, and When

TL;DR: Antenatal care follows a rough map: booking bloods early on, a dating scan around 11 to 14 weeks, screening tests, an anomaly scan around 20 weeks, a glucose test if you have risk factors, and growth checks later if needed. Each test has a clear purpose, and knowing what is coming makes appointments feel less like a blur. This is general education, not medical advice, and exact schedules vary by country and provider.

Pregnancy comes with a long list of appointments, tests, and scans, and it is easy to arrive at each one without quite knowing why you are there. Someone takes your blood, someone runs a wand over your belly, and you nod along. Understanding the map ahead of time changes that. It lets you show up ready, ask better questions, and know what a test is actually looking for.

This is a plain walkthrough of the tests and scans that usually come up across a pregnancy. We use the UK NHS schedule as a reference point because it is clear and public, but the timing and exact offer differ from country to country and clinic to clinic. Treat this as a guide to what to expect, not a checklist you must complete. Your midwife or doctor sets the plan that fits you.

The Booking Appointment and First Blood Tests

The first proper appointment is usually called the booking appointment, and the NHS suggests having it before you are 10 weeks pregnant where possible. It is longer than a normal visit, often around an hour, because this is where your history is taken and the routine blood tests start, according to the NHS guide to antenatal care and appointments.

Early blood tests typically check your blood group and rhesus status, look for anaemia, and screen for infections including HIV, hepatitis B, and syphilis. The NHS explains that these are offered early so that anything found can be managed in good time. You do not have to accept every test, and it is fair to ask what each one is for. If you are planning your very first visit and want to feel ready, our note on what to expect at a first gynaecologist appointment covers the general rhythm of these conversations.

The Dating Scan

The first ultrasound usually happens between 11 and 14 weeks and is often called the dating scan. Its main job is to confirm how many weeks along you are and give an estimated due date, based on the baby's measurements. The NHS notes that it also checks whether you are carrying more than one baby.

This scan can feel like the first real moment of seeing what is happening inside. It is also the point where screening for certain chromosomal conditions can begin, if you choose it, because part of that screening uses a measurement taken during this scan.

Screening Tests in the First Trimester

Around the same window, roughly 11 to 14 weeks, you may be offered the combined screening test. This brings together the dating scan measurement and a blood test to estimate the chance of certain chromosomal conditions, as the NHS screening guide describes.

It helps to be clear about what this is. Screening estimates a chance, it does not give a yes or no answer. A higher-chance result is not a diagnosis, and it usually leads to a conversation about further tests you can choose to have or decline. This is entirely your decision, and there is no wrong choice. If you would find it useful to walk into these appointments with your questions ready, our companion piece on genetic screening in pregnancy explained goes deeper, and our list of questions to ask at antenatal appointments can travel with you.

The 20-Week Anomaly Scan

The second routine ultrasound usually happens between 18 and 21 weeks and is often called the anomaly scan or mid-pregnancy scan. It is a detailed look at how the baby is developing, checking the growth and the way the body is forming. The NHS describes it as looking for a specific set of physical conditions, and it also checks the position of the placenta.

It is worth knowing ahead of time that no scan can find everything, and that is not a failure of the scan. Most of the time this appointment is reassuring. Occasionally it raises something that needs a closer look, and if that happens, you will be guided through what comes next rather than left to work it out alone.

Later Tests: Glucose and Growth

In the second half of pregnancy, the focus shifts to keeping an eye on you and the baby over time.

If you have certain risk factors, you may be offered a glucose tolerance test, usually between 24 and 28 weeks, to check for gestational diabetes. The NHS explains that this involves a fasting blood test, a sugary drink, and a second blood test a couple of hours later. Some of the risk factors, including a family history of diabetes and certain African, South Asian, and Middle Eastern backgrounds, mean this test is offered to many African women, so it is a good one to expect and understand. Gestational diabetes is common and manageable, and catching it is the whole point of the test.

Later on, some pregnancies also have extra growth scans if the midwife or doctor wants to keep a closer watch on how the baby is growing. These are not routine for everyone, and being offered one is not a cause for alarm on its own. Steady nutrition supports all of this, and our pregnancy nutrition guide covers the everyday basics.

A Word on Group B Strep

Group B streptococcus, usually shortened to GBS, is a common bacterium that many people carry without any symptoms. It matters in pregnancy because, in a small number of cases, it can pass to the baby around birth. The UK does not routinely screen every pregnant woman for it, and the NHS notes that it is often picked up by chance through another test. Practice varies widely between countries, with some offering routine swabs late in pregnancy. This is a reasonable thing to ask your provider about directly, so you know what your local approach is.

Knowing the Map Helps You Ask

None of these tests are things done to you. They are offered, and you get to understand and choose. Timing shifts from place to place, the exact tests differ, and your own plan may look different for good reasons. What stays the same is that you are allowed to ask why a test is happening, what it looks for, and what the options are afterwards.

Inside the Asele app, Amara can answer questions like these in Yoruba, Hausa, Igbo, Swahili, French, and English, so you can check something between appointments in the language you think in. For a warm and honest conversation about staying ahead of your care, the Blush and Bloom episode on proactive pregnancy care is a good listen, and our women's health screening checklist keeps the wider picture in view. If you want the app itself, it lives at Asele.

References

1. NHS. "Your antenatal care and appointments." nhs.uk
2. NHS. "Screening tests in pregnancy." nhs.uk
3. NHS. "Ultrasound scans in pregnancy." nhs.uk
4. NHS. "20-week screening scan." nhs.uk
5. NHS. "Gestational diabetes." nhs.uk
6. NHS. "Group B strep." nhs.uk
7. World Health Organization. "New guidelines on antenatal care for a positive pregnancy experience." who.int