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Pregnancy and baby

Antenatal checks and tests

What will happen to my body during pregnancy?

Media last reviewed: 20/03/2017

Next review due: 20/03/2020

During your pregnancy, you'll be offered a range of tests, including blood tests and ultrasound baby scans.

These are designed to:

  • help make your pregnancy safer
  • check and assess the development and wellbeing of you and your baby
  • screen for particular conditions

You don't have to have any of the tests – it's your choice. However, it's important to understand the purpose of all tests so you can make an informed decision about whether to have them. You can discuss this with your maternity team.   

Weight and height checks in pregnancy

You'll be weighed at your booking appointment, but you won't be weighed regularly during your pregnancy. Your height and weight are used to calculate your body mass index (BMI). 

Women who are overweight for their height are at increased risk of problems during pregnancy.

Find out more about being overweight when you get pregnant.

Most women put on 10 to 12.5kg (22 to 28lb) in pregnancy, largely after they are 20 weeks pregnant. Much of the extra weight is because the baby is growing, but your body also stores fat for making breast milk after birth. 

It's important to eat the right foods and do regular exercise during your pregnancy.

Antenatal urine tests

You'll be asked to give a urine sample at your antenatal appointments. Your urine is checked for several things, including protein. If this is found in your urine, it may mean you have an infection that needs to be treated. It may also be a sign of pre-eclampsia.

Pre-eclampsia affects 5% of pregnancies and can lead to a variety of problems, including fits (seizures). If left untreated, it can be life-threatening.

Pre-eclampsia can also affect the growth and health of the baby. Women with the condition usually feel perfectly well.

Blood pressure tests in pregnancy

Your blood pressure will be checked at every antenatal visit. A rise in blood pressure later in pregnancy could be a sign of pre-eclampsia.

It's very common for your blood pressure to be lower in the middle of your pregnancy than at other times. This isn't a problem, but it may make you feel lightheaded if you get up quickly. Talk to your midwife if you're concerned about it.

Find out more about high blood pressure and pregnancy.

Blood tests in pregnancy

As part of your antenatal care, you'll be offered several blood tests. Some are offered to all women while others are only offered if you might be at risk of a particular infection or condition.

All the tests are done to make your pregnancy safer or check that the baby is healthy, but you don't have to have them if you don't want to.

Talk to your midwife or doctor, and give yourself enough time to make your decision. They will also give you written information about the tests.

Screening for HIV, syphilis and hepatitis B

You'll be offered a blood test for three infectious diseases:

  • HIV
  • hepatitis B
  • syphilis

This is usually offered at an appointment with a midwife when you are around 8 to 12 weeks pregnant.

The tests are recommended to protect your health through early treatment and care, and reduce any risk of passing on an infection to your baby, partner or other family members.

Read more about screening for HIV, syphilis and hepatitis B.

Blood group and rhesus status

It's useful to know your blood group in case you need to be given blood – for example, if you have heavy bleeding (haemorrhage) during pregnancy or birth.

The test tells you whether you are blood group rhesus negative or rhesus positive. Women who are rhesus negative may need extra care to reduce the risk of rhesus disease.

Rhesus disease can happen if a pregnant woman who is rhesus negative develops antibodies that attack the baby's blood cells. This can lead to anaemia and jaundice in the baby.

If you're rhesus negative, you may be offered injections during pregnancy to prevent you from producing these antibodies. This is safe for both mother and baby.

Find out more about rhesus disease.   

Anaemia

Anaemia makes you tired and less able to cope with loss of blood when you give birth. You should be offered screening for anaemia at your booking appointment and at 28 weeks.

If tests show you're anaemic, you'll probably be offered iron and folic acid. 

Gestational diabetes

You may be at higher risk of developing diabetes in pregnancy (gestational diabetes) if you:

  • are overweight
  • have had diabetes in pregnancy before
  • have had a baby weighing 4.5kg (9.9lb) or more before
  • have a close relative with diabetes
  • are of southeast Asian, black Caribbean or Middle Eastern origin

If you're considered to be at high risk for gestational diabetes, you may be offered a test called the OGTT (oral glucose tolerance test). This involves drinking a sugary drink and having blood tests. 

The OGTT is done when you're between 24 and 28 weeks pregnant. If you've had gestational diabetes before, you'll be offered:

  • early self-monitoring of blood glucose levels, or
  • an OGTT earlier in pregnancy, soon after your booking visit, and another at 24 to 28 weeks if the first test is normal

Find out more about gestational diabetes.

Page last reviewed: 07/11/2017

Next review due: 07/11/2020

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