Pregnancy Complications

Authored by Dr Mary Harding, 30 Oct 2017

Patient is a certified member of
The Information Standard

Reviewed by:
Dr Jacqueline Payne, 30 Oct 2017

Pregnancy is a normal human event and happily most pregnancies are very straightforward. In some pregnancies, however, problems and complications can occur. This leaflet briefly lists some of the problems which can complicate pregnancy, and links to other leaflets where you can get more information.

Most pregnancies proceed perfectly normally, but possible problems include:

  • Infections which develop in pregnancy, or which you come into contact with whilst pregnant.
  • Medical conditions you already have which might need managing differently because you are pregnant.
  • Complications of the normal process of pregnancy.

It is impossible to list everything which could possibly cause problems in pregnancy, but the more common of these issues are discussed briefly below.


Pregnant women are more susceptible to some infections and more susceptible to complications of some infections. Also there is the effect on the developing baby to take into account. The following are some of the infections which might be encountered in pregnancy.

If you are pregnant you are more likely to get infections of the urinary tract. If you get an infection of the urinary tract whilst pregnant, you are more likely to develop complications. In pregnancy, urinary tract infections are treated a little differently than if you were not pregnant. Read more about urinary tract infections in pregnancy.

Chickenpox is such a common illness that there is a reasonable chance you might be in contact with someone who has chickenpox whilst you are pregnant. As long as you have had it yourself at some point, this is unlikely to be a problem. Read all about the problems chickenpox causes in pregnancy, and what you should do if you are in contact with chickenpox in pregnancy.

If you are pregnant, you are more prone to complications if you develop a tummy infection from food you have eaten (food poisoning). So, you should have a lower threshold than you might otherwise do for seeing a doctor. Some infections can directly harm your baby, in particular a germ called listeria. However, in most cases, a bout of food poisoning will be unpleasant but not harm you or your baby. See a doctor if:

  • You feel very unwell in yourself.
  • You have a high temperature (fever).
  • Diarrhoea persists for more than three days.
  • You are vomiting and can't keep fluids down.
  • You have blood in your poo (stool).
  • You have recently been travelling abroad.
  • You have severe tummy pain.
  • You have any bleeding from your vagina.
  • You have any concerns about yourself or your developing baby.

Toxoplasmosis is an infection with a parasite. It can be present in cat poo, so you can catch the infection from cleaning out cat litter trays. It can also be caught from handling contaminated soil, or eating contaminated food. In pregnancy, it is a particular concern because the infection can be passed to the developing baby and can harm the baby. See the separate leaflet called Toxoplasmosis to read more about how to avoid infection, the harm it can cause and how the infection is treated.

The Zika virus can be caught by being bitten by an infected mosquito. It usually causes a very mild illness, but if caught in pregnancy it may cause damage to the developing baby. You could be at risk if you travel to a country where Zika is currently a problem, or by having sex with somebody who has recently had the Zika virus. See the separate leaflet called Zika Virus to read more about this infection and the problems it may cause in pregnancy.

Parvovirus B19 is a common virus, which usually affects children, causing the mild illness known as slapped cheek disease. If you catch this infection in pregnancy, there is a risk in some cases of passing it on to your baby. It may cause you to have a miscarriage or it may cause harm to your baby, particularly if you get the illness in the first half of pregnancy. If you develop an illness with a temperature and a rash whilst pregnant, always see your doctor. You can be tested for this virus. If it turns out that you do have it, in some cases harm can be prevented by monitoring your developing baby. Fortunately, because this infection is so common, most adult women are already immune to it. So in fact, this is rarely a problem in pregnancy.

See the separate leaflet called Slapped Cheek Disease for more information.

Rubella (German measles) is usually a mild illness. However, if you are pregnant and catch rubella, it can cause serious damage to your unborn child. Before your first pregnancy you should have a blood test to check if you are immune to rubella. If you are not immune, you can be immunised before becoming pregnant, although you cannot be immunised once you are already pregnant. Read more about rubella and pregnancy.

Influenza, or "flu", is a common illness caused by a virus. Pregnant women are advised in the UK to have the flu vaccine to try to prevent catching flu whilst pregnant. This is because flu tends to cause more complications in pregnant women. See your doctor if you are pregnant and unwell with flu-like symptoms. See the separate leaflets called Influenza Immunisation and Influenza and Flu-like Illness for more information.

Human immunodeficiency virus (HIV) is a virus which attacks the body's immune system. If you have HIV, it is vital to discuss pregnancy with your specialist before becoming pregnant. The virus can be passed to your baby whilst you are pregnant, so you will need to think about this, and make plans with your specialist to reduce the risks of this occurring. This will include taking medication, and considering a caesarean section rather than a vaginal delivery. You and your baby would be carefully monitored throughout your pregnancy.

Pregnant women are tested for HIV as part of routine antenatal screening in the UK.

Read more about HIV in pregnancy.

Always see your doctor urgently if you are pregnant and develop an illness with a rash. Certain viruses which cause rashes can cause problems either for the mother, or for the developing baby or both. In addition to those discussed above, some viruses which might be encountered in pregnancy include:

  • Measles - can cause more complications when it occurs in pregnant women. If you catch measles in pregnancy you are more prone to miscarriage, stillbirth and early (premature) labour.
  • Cytomegalovirus (CMV) - can cause damage to the developing baby.
  • The Epstein-Barr virus (EBV) - causes glandular fever (infectious mononucleosis). It does not appear to cause harm to the baby if contracted during pregnancy.
  • The virus which causes hand, foot and mouth disease - it is not known to damage a developing baby.

The following are medical conditions which might need managing during pregnancy. You may already have one of these conditions, or it might develop for the first time whilst you are pregnant.

Pregnancy causes blood sugar (glucose) to go up. Women with diabetes need more treatment and more frequent checks during the pregnancy. Sometimes women who are not known to have diabetes need treatment for diabetes during the pregnancy. This is called gestational diabetes.

Diabetes in pregnancy can cause many problems for the mother and the baby. However, good treatment and regular checks can help you stay well and have a healthy baby.

Ideally is very important to see your doctor for advice before becoming pregnant if you have diabetes and want to have children. Making sure your diabetes is very well controlled before pregnancy helps you have a healthy baby.

Read more about diabetes and pregnancy.

If you have epilepsy, it is extremely important to discuss your medication with your specialist before becoming pregnant. If this has not been possible, do so as soon as possible after you discover you are pregnant. Some medicines for epilepsy can harm your baby when you are pregnant, so it may be that you need to change your medication. Equally, having fits whilst pregnant could harm the baby, so it is important for your condition to be stable on the right medication. You will also be advised to take a higher dose of folic acid (5 mg) than most women, before conceiving and until you are 12 weeks pregnant.

Read about epilepsy and planning pregnancy.

If you are pregnant you should have regular blood pressure checks. Most women will not develop any problems with their blood pressure during pregnancy. However, in some women, high blood pressure (hypertension) can develop. It is often mild and not serious. But in some cases, high blood pressure can become severe and can be harmful to both the mother and the baby. Some women with high blood pressure during pregnancy develop pre-eclampsia which is a more serious condition. Read more about high blood pressure in pregnancy.

If you have an underactive thyroid gland (hypothyroidism) and become pregnant, you may need different doses of your medication (levothyroxine). You would normally be under the care of a specialist who will monitor your blood tests regularly and adjust accordingly. Levothyroxine is safe to take in pregnancy.

If you have an overactive thyroid gland (hyperthyroidism) it is wise to discuss your medication before becoming pregnant ideally. The choice of treatment used may be different if you become pregnant, and the dose may be different. Again, close monitoring of your thyroid blood tests will be needed.

Generally speaking, if your condition is well controlled, it will not cause any problems for you or your baby.


The following are some of the possible complications which can occur in pregnancy.

The "afterbirth", or placenta, sits on the wall of your womb during pregnancy, and is linked through the umbilical cord to your growing baby. If it lies low down over the opening (neck) of the womb (the cervix), it is known as placenta praevia and can cause problems. If the placenta is over the cervix as it opens for labour, there would be heavy bleeding. If it does lie over the cervix, you would have to have a planned caesarean section in advance to avoid this happening. Mostly, low lying placentas move up to be free of the cervix as the womb expands, and a caesarean section is not needed.

The position of the placenta is noted on your routine ultrasound scan at around 20 weeks of pregnancy. If it is over the cervix, it will be checked later in pregnancy to make sure it has moved. In the unlikely event that it has not, you would be given further advice and you and your baby would be monitored by ultrasound scan.

Placental abruption is the name for the placenta coming away from the wall of the womb before delivery. This causes bleeding, which may be within the womb, or which you may see from the vagina. You would experience pain in your tummy, or bleeding from your vagina, or both. This is an emergency and you should contact the labour ward immediately to be seen.

Antepartum haemorrhage is bleeding from the vagina after the 24th week of pregnancy. (Bleeding before this time is referred to as threatened miscarriage.) The most common causes are placenta praevia and placental abruption as discussed above. There are a number of less common causes, including trauma. Always contact your doctor or labour ward immediately if you have bleeding from the vagina after 24 weeks of pregnancy.

If you start going into labour before 37 weeks, this is called premature labour. See the separate leaflet called Premature Labour.

Your blood group is determined by the genes you inherit from your parents. As well as being blood group A, B, AB or O, you are also either rhesus (Rh) positive or negative. If you are pregnant, and your blood group is Rh negative, and your baby is Rh positive, this can cause problems. In this situation, your immune system recognises the baby's blood cells as different and makes proteins called antibodies to attack them. This means some of the baby's blood cells are destroyed, causing anaemia. Immune systems must first be sensitised to recognise the different Rh positive cells, so this only happens if you are Rh negative and have previously been sensitised - for example, in a previous pregnancy. If not treated this causes rhesus disease of the newborn baby (haemolytic disease of the fetus and newborn).

Fortunately this is usually picked up well in advance. Your blood group is checked at your first antenatal appointment. If you are Rh negative, you will be offered injections of anti-D immunoglobulin. These injections help to stop your immune system making the antibodies which can attack your baby's blood cells. You have them at times when your body might produce antibodies - for example, if you have any bleeding. You would also have them in other pregnancy circumstances where antibodies might be produced, such as after an ectopic pregnancy or a termination of pregnancy. Once the antibodies have been produced, the anti-D injections can't help. If you are Rh negative, you will also have a test to check for Rh antibodies. If this is positive, your baby will be carefully monitored. Treatment may be needed for the baby either after delivery, or whilst you are still pregnant.

Pre-eclampsia is a serious condition that can occur in pregnancy, usually after 20 weeks. It is a combination of high blood pressure (hypertension), with protein "leak" from your kidneys into your urine. Other symptoms, including swelling, are common. Pre-eclampsia can also affect your baby's growth in the womb (uterus).

HELLP syndrome is a severe form of pre-eclampsia, in which your blood cells and liver are affected and further symptoms develop. Severe cases of pre-eclampsia and HELLP syndrome can progress to eclampsia, which causes fits (convulsions) in addition to the symptoms of pre-eclampsia or HELLP syndrome.

Read about pre-eclampsia, eclampsia and HELLP syndrome.

Obstetric cholestasis, also called intrahepatic cholestasis of pregnancy, is one cause of itching in pregnancy. It is caused by a liver problem in pregnancy where the bile does not flow as normal from the liver to the guts. Read about obstetric cholestasis.

Further reading and references

Listen