Infections in pregnancy

Infections are a part of normal life. We all suffer from the odd coughs and colds, and many women have experienced troublesome thrush or cystitis. Pregnancy is a time when some infections are more common than usual, and a time when other infections can present a particular risk either to the woman or her unborn baby. This two part series will review the more common and problematic infections that might affect pregnancy.

Coughs, colds & ‘flu

Women are just as likely to get these during pregnancy. They are little threat to the pregnancy itself and all that is needed is symptom relief: lots of fluids, rest & TLC. Inhaled decongestants are safe, but cough linctus should be avoided. It is quite safe to take paracetamol up to normal maximum doses (1g, four times per day). If a cough becomes productive with green phlegm, this may mean a bacterial infection needing antibiotics. There are antibiotics that are safe during pregnancy, so be sure to tell any doctor you see that you are pregnant.

Urinary tract (water) infections

Urinary tract infections (UTI’s) are more common during pregnancy than at other times, mostly because of a slowing down of the urine flow on its way from the kidney to the bladder. Around 1 in 25 women get a UTI during pregnancy, the common symptoms being a discomfort or burning sensation on passing urine, an aching pain over the bladder or needing to pass water very frequently. This last symptom is unfortunately very common in pregnancy anyway and is not very reliable in making the diagnosis. If the infection passes up to the kidneys and into the blood stream (pyelonephritis or septicaemia) it causes loin pain, vomiting, a fever and can even start premature labour. By treating early UTI’s, kidney infections and their complications can be prevented. The infection is diagnosed by looking at the urine under a microscope and seeing if a bug can be grown from the sample. This can also confirm which antibiotic is the best to use. A mild infection is treated with a course of antibiotic tablets for at least a week, but a more severe one would need admission to hospital, intravenous antibiotics and rest. After one UTI, further infections are more common and monthly checks on the urine are suggested, to see if one is developing even before symptoms appear.


Toxoplasmosis is caused by a parasite called toxoplasma gondii. This is found in different forms in raw meat, within cats that eat raw meat and their faeces. Toxoplasmosis infection is common in both men and women outside of pregnancy, however it is infection during pregnancy that is of most concern as it can lead to infection in the unborn infant: congenital toxoplasmosis. Once you have had toxoplasma infection, the bodies immunity will prevent you catching it again. Around 30% of women will have already had a toxoplasma infection before pregnancy. It typically causes a flu-like illness with swollen glands in the neck. Most people are unaware that it was in fact toxoplasmosis. It is not known for sure how many women catch toxoplasmosis during pregnancy, but some research suggests it is of the order 2 in every 1000, which means about 1400 each year in the UK.

In only about 30-40% of women who catch toxoplasmosis during pregnancy, does the infection pass to the unborn baby. The actual risk appears to be related to the gestation at which it is acquired. It is greatest in the third trimester at 70%, whereas in early pregnancy only 15% of infants will become infected. Toxoplasmosis infection may lead to miscarriage, stillbirth, or survival with growth problems, blindness, water on the brain (hydrocephalus), brain damage, epilepsy, or deafness. If a woman is found to have acquired toxoplasmosis during pregnancy, she will be offered an ultrasound scan to look for signs of foetal infection. After 20 weeks gestation, she may be offered a definitive test – cordocentesis. This involves a scan and blood sample being taken from the umbilical cord.

Although toxoplasmosis is quite serious when it occurs, as you will see from the figures above, it is relatively rare. Women with cats do not need to get rid of them when they become pregnant; it is just necessary to take a few precautions. Be sure to only eat meat that has been cooked right through. Wash your hands, cooking utensils and food surfaces after preparing raw meat and wash all the soil from fruit and vegetables before eating. Keep raw meat and cooked foods on separate plates. If possible get someone else to clean out the dirty cat litter or use gloves and wash your hands afterwards. Always use gloves when gardening and wash your hands afterwards.

Chicken pox

It’s not uncommon for women who are pregnant to come into contact with someone who has chicken pox. This can cause great worry, but it is uncommon for there to be a problem. Firstly, if you have definitely had chicken pox before, there is no risk to the baby. In any case, even if you don’t recall having had chicken pox, it is likely you have antibodies (80% do) from a silent infection. So if there’s any doubt about it, you should see a doctor for a blood test to check for immunity. Sometimes the laboratory can use the stored blood taken at booking to speed this up.

Risks to the baby are important at the following two times, only if mum gets chicken pox:
1. Before 20 weeks – risk of chicken-pox syndrome. This is actually quite rare. Up until 14 weeks the risk is about 0.4%, whereas between 14-20 weeks it is 2%. If a woman has VZ-Ig treatment (see below) after being exposed, the risk is even lower.
2. Mum’s rash developing within a week before delivery to a month afterwards. It takes about a week for mum to pass the protective antibodies to the baby, so if born before that time, the baby is at risk of overwhelming infection after birth.

Between 20 weeks and term there is no risk to the baby.

VZ-Ig is a form of antibody treatment that can reduce the risk of chicken-pox syndrome and should be given by 10 days after the initial attack.

Vaginal infections

Pregnancy makes a woman more likely to get a thrush infection, most commonly caused by the yeast Candida albicans. This yeast is commonly found in the vagina in up to 16% of non-pregnant women and 32% during pregnancy. It does not always cause symptoms and only requires treatment if it causes troublesome itching, soreness or the typical thick, white discharge. It is more common in second and subsequent pregnancies, in the third trimester, during summer months, following a course of antibiotics and in diabetic women. Treatment with Clotrimazole (Canesten) vaginal suppositories is usually effective. The tablet treatment Fluconazole (Diflucan) is not advised during pregnancy. Thrush isn’t a sexually transmitted infection and there is no need for treatment of your partner.

Group B streptococcus (GBS) is a bacterium that around 15-20% of pregnant women carry in the vagina, usually causing no problems at all. In a small number of cases the bug is passed to the baby during delivery and it can lead to a blood-borne infection or even meningitis. This condition affects only 3 per 10,000 babies in the UK. The incidence is much higher in the US, so they have developed a comprehensive screening programme for GBS. In the UK treatment is usually only advised in one of a number of ‘high risk’ scenarios. These include: early labour (before 37 weeks), prolonged or early rupture of the membranes, if there is a temperature during labour or if a previous baby has been affected with the condition. The treatment involves antibiotics through a drip during labour – tablet treatment cannot reliably eradicate the infection.

Sexually transmitted infections

Both chlamydia and gonorrhoea infections can pass to the baby during delivery causing eye infections. Gonorrhoea is quite rare in the UK, occurring in less than 1 per 1000 women. Chlamydia is more common, affecting around 5% of pregnancies. It can also lead to chest infections in the baby or infections of the lining of the womb for the mother after delivery. Both of these infections are treatable during pregnancy but a second swab should be taken afterwards to confirm that they are cleared. It is most important to screen and treat sexual partners, otherwise they will pass the infection back again.

Genitourinary medicine clinics (previously known as STD or VD clinics) have come a long way since the 1970’s. They are really sexual health clinics and many young women use them for smear tests, contraceptive advice or any unusual vaginal itch or discharge – not necessarily sexually transmitted. They have facilities not available to GP’s, obstetrician or gynaecologists and are the best place to go for any vaginal discharge that proves troublesome to clear.

Testing for HIV infection is routine in some hospitals, but is not usual outside of high-risk areas. If you feel that you may have been at risk, any GUM or hospital clinic will be able to arrange one, often the same day if necessary. HIV infection passes to the baby in about 15% of cases, but this can be reduced to 8% with drug treatment and perhaps even lower with an elective caesarean section, so there is definitely a benefit to knowing for sure if you are concerned.

Genital herpes

Herpes infections affect about 10% of the UK population, though only in one third of cases is an actual diagnosis as such made. It usually presents initially with a flu-like illness, followed by an outbreak of vulval sores, which are very painful and swollen glands in the groin. By a week to 10 days later these have usually healed over. Sometimes the initial attack is mistaken for a thrush infection, just causing an itch or soreness, seemingly responding to cream or pessaries. Occasionally it is completely without symptoms at all. The first (primary) attack is usually the most painful. The herpes virus stays in the nerve in the spine and can reactivate causing a secondary attack. This occurs on average at 3-4 months after the first one, and recurrences return on average 2-3 times per year, but this is extremely variable.

The risk of herpes to pregnancy is greatest if the primary attack occurs after 28 weeks. The mother’s initial antibody response can take up to 12 weeks to fully develop. Secondary attacks are much less of a risk. The risk of herpes is passing the infection to the baby at the time of delivery. Primary attacks also can lead to early labour or poor growth. Because of these risks, a caesarean section is usually advised at term if a primary attack occurs during pregnancy after 28 weeks, or if there is an active secondary attack at the time of labour.

Further information on GBS, chicken pox, toxoplasmosis and parvovirus (Fifth’s disease) can be found at the Women’s Health site

Article by Dr Danny Tucker MBBS, MRCOG – a Specialist Registrar in Obstetrics & Gynaecology from Sheffield.

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