Blood groups and red cell antibodies in pregnancy

Routine checks and tests

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

These tests are designed to help make your pregnancy safer, check and assess the development and wellbeing of you and your baby, and screen for particular conditions.

You don't have to have any of the tests. However, it's important to understand the purpose of all tests so that you can make an informed decision about whether to have them. Discuss this with your maternity team. You'll be given written information about the screening tests offered (this is also available online at the UK National Screening Committee website).   

Weight and height

You will asked to be weighed at your booking appointment. Your height and weight are used to calculate your BMI (body mass index). Women who are overweight for their height are at increased risk of problems during pregnancy. 

Most women put on 10-12.5kg (22-28lb) in pregnancy, most of it after they are 20 weeks pregnant. Much of the extra weight is due to the baby growing, but your body also stores fat for making breast milk after the birth. During your pregnancy, it's important to eat the right foods and exercise regularly.

You will not be asked to be weighed regularly during your pregnancy, unless you have diabetes or a high BMI.

Urine

You'll be asked to give a urine sample at your antenatal appointments. Your urine is checked for several things, including protein or albumin. If this is found in your urine, it may mean that 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 seizures (fits). 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, so it is important you have this test.

Blood pressure

Your blood pressure will be taken at every antenatal visit. A rise in blood pressure later in pregnancy could be a sign of pregnancy-induced hypertension. 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.

Blood tests

As part of your antenatal care you'll be offered several blood tests. Some are offered to all women, and some are only offered if you might be at risk of a particular infection or inherited condition. All the tests are done to make your pregnancy safer or to 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.  

Blood group

It is 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

People who are rhesus positive have a substance known as D antigen on the surface of their red blood cells. Rhesus negative people do not. A rhesus negative woman can carry a baby who is rhesus positive if the baby's father is rhesus positive. If a small amount of the baby's blood enters the mother's bloodstream during pregnancy or birth, the mother can produce antibodies against the rhesus positive cells (known as anti-D antibodies).

This usually doesn't affect the current pregnancy, but if the woman has another pregnancy with a rhesus positive baby, her immune response will be greater and she may produce a lot more antibodies. These antibodies can cross the placenta and destroy the baby's blood cells, leading to a condition called rhesus disease, or haemolytic disease of the newborn. This can lead to anaemia and jaundice in the baby. 

Anti-D injections can prevent rhesus negative women from producing antibodies against the baby. Rhesus negative mothers who haven't developed antibodies are therefore offered anti-D injections at 28 weeks of pregnancy, as well as after the birth of their baby. This is safe for both the mother and the baby.  

Anaemia

Anaemia makes you feel tired and less able to cope with loss of blood when you give birth. If tests show that you're anaemic, you'll probably be given iron and folic acid. 

 

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