During pregnancy your blood is drawn a few times, usually at the first check-up and around week 27. That blood testing looks at your blood group, your haemoglobin (Hb), your blood sugar and whether you are protected against certain infections. Together these values give a picture of how you and your baby are doing.
This is the overview article in our series on blood testing in pregnancy. I notice that many pregnant women do have blood drawn, but do not really know what is measured and why. Below you will read which tests are standard, when they happen, what the main values mean and when an extra test can be useful. For the details per topic, see the separate articles in this series.
Which blood tests are standard during pregnancy?
In the Netherlands every pregnant woman is offered a standard blood test at the start of pregnancy, the so-called PSIE screening. According to the RIVM, this determines your blood group and rhesus factor, and checks for hepatitis B, HIV and syphilis. Around week 27 many women have a second draw.
Your midwife or gynaecologist arranges this testing. It is free and voluntary, and most women take part. The table further down shows which values are looked at when and what they reveal.
Besides this standard package, there can be reasons to test more, for example with complaints, a previous pregnancy with complications or a raised risk of gestational diabetes. What is useful for you is decided together with your midwife or doctor.
When is your blood drawn during pregnancy?
Blood testing happens at fixed moments. The first time is at the intake, usually around week 8 to 10. The second time is around week 27, if your blood group is rhesus D negative or to check for anaemia and gestational diabetes.
These moments are not chosen at random. Anaemia is more common in the second and third trimester, because your blood volume rises sharply. Gestational diabetes usually develops only halfway through pregnancy, when the placenta makes many hormones that counteract insulin.
Which blood values are checked and what do they say?
Blood testing in pregnancy revolves around a handful of values. Each value says something different: about your immunity, your iron stores, your blood sugar or the blood group of you and your baby. The table below links each value to the moment it is usually checked and to what the result shows.
| Value | When | What it shows |
|---|---|---|
| Blood group and rhesus factor | First check-up | Whether you are rhesus D positive or negative, important for protecting your baby |
| Haemoglobin (Hb) | First check-up and week 27 | Whether there is anaemia |
| Ferritin | On indication | The size of your iron stores |
| Glucose | Week 24 to 28 (on indication) | Whether your blood sugar is too high (gestational diabetes) |
| TSH | On indication | Whether your thyroid works well |
| Infectious diseases (hepatitis B, HIV, syphilis) | First check-up | Whether treatment is needed to protect your baby |
Most of these values fall within the standard package from your midwife. Ferritin, glucose and TSH are often only tested on indication, for example with complaints or a raised risk. In the separate articles in this series we go deeper per topic.
Anaemia: haemoglobin and ferritin
Anaemia is common in pregnancy. Your blood volume rises by about half, which dilutes the haemoglobin level. According to the World Health Organization there is anaemia at a Hb below 110 grams per litre in the first and third trimester.
A low Hb is often caused by a shortage of iron. Your baby needs a lot of iron, especially in the third trimester. So your midwife looks at your Hb, and sometimes at your ferritin, which shows the size of your iron stores. Read more about anaemia in pregnancy and which iron values to test.
Gestational diabetes: glucose and the sugar test
Gestational diabetes means your blood sugar becomes too high during pregnancy. It usually develops after week 24, when the placenta makes hormones that reduce insulin action. With a raised risk, a sugar test (OGTT) is done between week 24 and 28.
In that test your fasting glucose is drawn, after which you get a sugar drink and are drawn again after one or two hours. This shows how your body handles sugar. What the values mean exactly you can read in our article on the gestational diabetes test and blood values.
Thyroid: why TSH can matter
Your thyroid works harder than usual during pregnancy. A thyroid that is too slow or too fast can affect the course of the pregnancy. So with complaints or a known thyroid condition, the TSH value is tested.
TSH is not tested in everyone as standard, but it is when there is a reason, for example a previous thyroid condition or matching complaints. In our article on thyroid and pregnancy we explain what the TSH value shows and which reference ranges apply.
Blood group and rhesus factor
At the first check-up your blood group and rhesus factor are determined. If you are rhesus D negative and your baby rhesus D positive, your body can make antibodies against your baby's blood. To prevent this, rhesus-negative women get an injection (anti-D) around week 27 and after birth.
This is one of the reasons the blood group test happens so early. Read more in our article on blood group and rhesus factor in pregnancy.
Folic acid and vitamins around pregnancy
Folic acid is one of the few supplements that the Voedingscentrum and the Gezondheidsraad actively advise around pregnancy. It lowers the chance of spina bifida and other neural tube defects in the baby. A Cochrane review of five studies found a clear protective effect (De-Regil et al., 2015).
The advice is to take 400 micrograms of folic acid daily from when you start trying until week 10. Vitamin D is also often recommended. These supplements are something other than the blood values your midwife checks, but they belong to the same picture of a healthy start.
Blood testing or prenatal screening: what is the difference?
Blood testing and prenatal screening are often mixed up, but they have a different aim. The standard blood testing looks at your health, such as your blood group, your Hb and whether you are protected against certain infections. Prenatal screening focuses instead on the health and development of your baby.
The NIPT (non-invasive prenatal test) is also a blood test, but with a different aim than the regular testing. It looks in your blood at genetic material from the placenta, for example for Down syndrome. The 13-week scan and the 20-week scan are not blood tests, but ultrasound examinations.
In short: not every draw or test is about the same thing. Your midwife explains which test is meant for what and what is voluntary. That way you can calmly choose what you take part in and why.
Blood testing before pregnancy: preconception
Some blood values are actually interesting before you get pregnant. Think of your iron stores (ferritin), your thyroid (TSH) and your vitamin D. A favourable starting point can be pleasant when you begin a pregnancy, although nothing is a guarantee.
The Voedingscentrum advises starting folic acid as soon as you wish to conceive, so before you are pregnant. Your lifestyle is part of that preparation too, such as stopping smoking and moderating alcohol. A blood test is an aid in this, not an obligation.
If you want to map your fertility and hormones, also read what is best to test when trying to conceive. You always discuss an abnormal result with your GP or midwife, who look at your whole situation.
How do you prepare for the blood draw?
For most blood tests in pregnancy you need to do little. You usually do not have to be fasting, except for a glucose test like the OGTT. Wear comfortable clothing with sleeves you can push up easily.
Feel free to drink some water before your appointment, because being well hydrated often makes the draw a bit easier. Bring your midwife's details if you are asked for them. If you feel tense about the draw, just let the staff member know.
After the draw you can usually just continue your day.
Testing your own blood around pregnancy
The standard blood testing runs through your midwife or gynaecologist. If you also want to map a number of values yourself, for example before you get pregnant or between check-ups, you can do so at Lunara without a referral. The Pregnancy Blood Test and the Prenatal Essentials look at values like Hb, ferritin and TSH.
Important: testing yourself does not replace the regular pregnancy check-ups. It is meant as an addition and as a starting point for a conversation with your midwife or GP. You always discuss an abnormal result with a professional. Thinking about getting pregnant? Then also read what is best to test when trying to conceive.
Frequently asked questions
How often is your blood drawn during pregnancy?
Usually twice: at the first check-up around week 8 to 10 and again around week 27. With complaints or a raised risk, blood may be drawn more often. Your midwife decides together with you what is needed.
Is blood testing in pregnancy mandatory?
No, it is voluntary. The standard blood testing is offered and free, but you may decline it. Most women take part because it protects you and your baby.
What does a pregnancy blood test cost?
The standard testing through your midwife falls under insured care and costs you nothing. An additional test you arrange yourself, for example at Lunara, you pay for yourself. The price depends on which values you test.
Can you see gestational diabetes in a regular blood test?
A single glucose value gives a first impression, but the diagnosis of gestational diabetes is made with a sugar test (OGTT), where you are drawn fasting and after a sugar drink. Discuss with your midwife whether that test is useful for you.
Does drawing blood harm my baby?
No. At the pregnancy check-ups blood is drawn from your arm, not from the baby. For you it feels like an ordinary prick, and your baby notices nothing of it. If you feel unsure, discuss it with your midwife.
Do I have to be fasting for blood testing in pregnancy?
For most standard tests you do not have to be fasting. For a glucose test (OGTT) you do, because your fasting blood sugar is measured then. Your midwife or the draw location will let you know whether fasting is needed.
References
- De-Regil LM, Peña-Rosas JP, Fernández-Gaxiola AC, Rayco-Solon P. Effects and safety of periconceptional oral folate supplementation for preventing birth defects. Cochrane Database Syst Rev. 2015;(12):CD007950. PMID: 26662928.
- RIVM. Prenatal screening for infectious diseases and erythrocyte immunisation (PSIE). National Institute for Public Health and the Environment.
- World Health Organization (WHO). Haemoglobin concentrations for the diagnosis of anaemia. WHO, 2011.
- Voedingscentrum and Gezondheidsraad. Folic acid and vitamin D around pregnancy.
- NHG and Thuisarts.nl. Pregnancy and blood testing. Dutch College of General Practitioners.
Every blood test result through Lunara includes a professional assessment by a BIG-registered doctor. Blood testing through Lunara does not replace the regular pregnancy check-ups. For treatment decisions, discuss your results with your GP or midwife.
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