First-trimester blood and urine tests: what each one is for

Being handed a long list of tests at your first visit can feel like a lot. Take a breath: most of these tests are routine, and the point is less about looking for trouble than about catching anything early so that you and your baby are protected.

Blood group and Rh factor

Your blood group and Rh status are determined. If you are Rh negative and your partner is Rh positive, your blood and your baby's blood may not match, and knowing this means follow-up and precautions can be planned ahead. For Rh-negative women an antibody screen (indirect Coombs test) is done; according to the guideline it is repeated at week 28 if the result is negative. If it is needed, a protective injection is planned by your doctor.

Blood count

Haemoglobin and haematocrit are measured to screen for anaemia. Because your blood volume rises in pregnancy, your iron needs go up too. If your values are low, your doctor will suggest a suitable plan. The blood count is repeated at later visits.

Urine test

The urine is checked for bacteria and protein. Some urinary infections cause no symptoms, yet treating them in pregnancy matters. If your doctor wishes, a urine culture can also be done early on. Checking protein helps pick up blood-pressure-related problems later in pregnancy.

Infection screening

Infections that can pass from mother to baby, such as hepatitis B (HBsAg), HIV and syphilis, are screened with a blood test, and immunity to rubella is checked. A negative result is by far the most common outcome. If an infection is found early, effective steps to protect the baby can often be taken, and that is exactly the purpose. The full list of tests may differ a little between clinics and doctors.

Thyroid and urine culture

The thyroid test (TSH) and a urine culture appear among the first-visit tests in the ministry guideline, but in practice they can vary between clinics and doctors. Your doctor will order them in particular if you have a thyroid history, symptoms or another risk factor. If they were not requested for you, you can simply ask why.

Reading the results

Lab sheets show reference ranges, but some values behave differently in pregnancy than outside it. That is why it is wiser to go over the results with your doctor than to interpret them alone. A single value outside the range often just leads to a repeat test and is not a final answer.

What you can do

• Ask whether you need to fast for the blood draw; not every test requires it.
• Keep your result sheets and bring them to later visits.
• Ask about any term you do not understand.
• Show earlier records of blood group, vaccinations or illnesses if you have them.
• While you wait, try not to brace for results; most come back routine and unremarkable.

When to contact your doctor

Do not wait for results if you notice:

• Fever, chills or burning when you pass urine
• Vaginal bleeding or severe abdominal pain
• Marked tiredness, a racing heart, shortness of breath or dizziness
• Yellowing of the skin or eyes
• A rash, or contact with someone who may have rubella

In a serious situation, call 112. This article is for information only; your doctor decides which tests are right for you.