Pregnancy blood tests and scans, what each one checks

Why tests and scans matter

Antenatal tests are not just routine boxes to tick. They help your care team check how your pregnancy is progressing, spot problems early, and confirm important details about your baby and your own health. Some tests are used to screen for possible concerns, while others are used to diagnose a condition more clearly.

It is normal to feel a little unsure about why each test is needed. Knowing what is being checked can make appointments feel more manageable and can help you ask better questions.

The main blood tests in pregnancy

Blood tests are usually done early in pregnancy, then repeated if needed. They can check for conditions that may affect you or your baby, including anaemia, blood group issues, and certain infections.

A common early pregnancy blood panel includes:

• Full blood count, to look for anaemia or signs of infection
• Blood group and Rh factor, to see whether you are Rh negative or Rh positive
• Antibody screen, to check for antibodies that could affect the baby
• Tests for infections such as HIV, hepatitis B, syphilis, and sometimes hepatitis C, depending on local guidance
• Rubella immunity in some settings, because infection in pregnancy can be serious

If your haemoglobin is low, your care provider may recommend iron-rich foods, an iron supplement, or further testing. Anaemia is common in pregnancy, and treating it can improve energy levels and support a healthier birth.

Screening for gestational diabetes and other conditions

Depending on your risk factors and where you live, you may be offered screening for gestational diabetes between 24 and 28 weeks. This often involves a blood sugar test after a sugary drink or a fasting blood test, followed by more testing if needed.

Gestational diabetes does not always cause symptoms, which is why screening can be helpful. If it is detected, it can often be managed well with nutrition changes, physical activity, monitoring, and sometimes medication.

Your provider may also check your urine during visits for protein, sugar, or signs of infection. A urine test is a simple way to look for issues that can be missed if you only go by symptoms.

The first ultrasound, what it shows

The first ultrasound is often one of the most exciting moments in pregnancy. It is usually done in the first trimester or early second trimester, depending on local practice and the reason for the scan.

This scan may be used to:

• Confirm the pregnancy is inside the uterus
• Estimate how far along you are and set a due date
• Check how many babies you are carrying
• Look for a heartbeat
• Assess early development

If your periods are irregular or you are not sure when you conceived, an early scan can be especially useful for dating the pregnancy more accurately. That can help later with timing other tests and planning antenatal care.

The nuchal translucency and early screening tests

Some people are offered an early screening scan, often around 11 to 14 weeks, sometimes called a nuchal translucency scan. It measures a small fluid space at the back of the baby’s neck and may be combined with blood tests to estimate the chance of certain chromosomal conditions.

In some places, this has been partly replaced or complemented by non-invasive prenatal testing, or NIPT, which analyses small amounts of fetal DNA in the mother’s blood. NIPT is a screening test, not a diagnosis, but it can provide a more accurate risk estimate for certain chromosome differences.

If a screening result suggests a higher chance of a condition, your care team may discuss diagnostic tests. These can include chorionic villus sampling or amniocentesis, which give more definite answers but also carry a small procedure-related risk.

The anatomy scan, a closer look at development

The detailed anatomy scan is usually offered around 18 to 22 weeks. This is one of the most important ultrasounds in pregnancy because it looks carefully at the baby’s body structures and checks growth and placental position.

During this scan, the sonographer may assess:

• The brain, face, spine, heart, and stomach
• Arms, legs, hands, and feet
• The placenta and amniotic fluid level
• Growth and overall development
• In some cases, the cervix or uterus if there are concerns

This scan cannot detect every problem, but it can identify many structural differences. If something is not seen clearly, you may be asked to return for a repeat scan. This is common and does not always mean there is a problem.

Later pregnancy checks, growth, position, and wellbeing

As pregnancy progresses, your care team will check that the baby is growing well and is in a good position for birth. This may be done by feeling your abdomen, measuring the fundal height, or repeating ultrasounds if there are concerns.

Additional scans may be suggested if you have:

• High blood pressure
• Gestational diabetes
• Previous growth issues in pregnancy
• Concerns about baby’s movements
• A placenta that was low lying earlier in pregnancy
• A pregnancy with twins or more

In late pregnancy, a scan may look at the baby’s position, estimate size, and check the placenta and fluid levels. Some clinics also use Doppler studies to assess blood flow when growth concerns are present.

What the results can and cannot tell you

It is important to remember that screening tests estimate risk, they do not give a final answer. A low-risk result is reassuring, but it does not guarantee that everything is perfect. A higher-risk result does not mean there is definitely a problem, only that more testing or follow-up may be useful.

Ultrasounds are also limited by timing, baby’s position, maternal body shape, and the quality of the image. Sometimes a normal scan can still miss a condition, and sometimes a suspicious image turns out to be completely normal on repeat viewing.

If a result is unclear, ask what it means in practical terms. Helpful questions include:

• What exactly was checked?
• Is this a screening test or a diagnostic test?
• What is the next step, if any?
• Is there anything I should watch for at home?
• When will I get the result, and who will explain it?

How to prepare for appointments

A little preparation can make appointments less stressful. Consider bringing:

• Your pregnancy notes or app details
• A list of medications, supplements, and allergies
• Any previous scan or test results
• Questions you want to remember

If you are anxious about blood tests or scans, tell the staff. They can often explain what will happen, give you time to ask questions, and help you feel more comfortable. If you prefer, bring someone with you for support, if local rules allow.

When to seek advice sooner

Contact your maternity care provider promptly if you notice heavy bleeding, severe abdominal pain, fever, leaking fluid, painful urination, or reduced fetal movements later in pregnancy. Do not wait for the next routine appointment if something feels wrong.

Also reach out if you miss a scheduled test and are unsure whether it still needs to be done. Many screenings are time sensitive, and it is better to check than to assume you have missed the window.

A practical takeaway

Pregnancy tests and scans are most useful when you understand what each one is for. Blood tests check your health, screening tests estimate risk, and ultrasound scans help track development and wellbeing. You do not need to memorise every detail, but it helps to know that each appointment has a purpose.

If you ever feel confused by a result, ask for a plain language explanation and the next step. Clear information can reduce worry and help you feel more confident as you move through pregnancy.