The hepatitis C virus (HCV) is an RNA virus.
Acquisition of the virus occurs predominantly through infected blood products and injection of drugs. It can also occur with tattooing and body piercing. Mother-to-child transmission can occur due to contact with infected maternal blood around the time of delivery, and the risk is higher in those coinfected with HIV.
Sexual transmission is extremely rare.
Prevalence
In the UK the overall antenatal prevalence has been estimated to be around 1 per cent, with regional variation. The risk of mother-to-child transmission is estimated to lie between 3 and 5 per cent and it is estimated that 70 births each year are infected with HCV as a result of mother-to-child transmission in the UK. The risk of mother-to-child transmission of HCV increases with increasing maternal viral load.
for HIV antibodies. For this reason, direct viral amplifi cation by PCR is used for the diagnosis of infant infections. Typically, tests are carried out at birth, then at 3 weeks, 6 weeks and six months.
Hepatitis B Infective organism
The hepatitis B virus (HBV) is a DNA virus that is transmitted mainly in blood, but also in other body fl uids such as saliva, semen and vaginal fl uid. Drug users who share needles are at high risk. In some areas in the world, e.g. China, chronic hepatitis B is prevalent and vertical transmission is very common.
Prevalence
Two billion people worldwide are infected with HBV. More than 350 million have chronic (lifelong) infections.
In the UK, approximately one in 1000 people are thought to have the virus. The prevalence of hepatitis B surface antigen (HBsAg) in pregnant women in the UK has been found to range from 0.5 to 1 per cent.
There is wide variation in prevalence among different ethnic groups, and oriental women in particular appear to have a higher prevalence of HBsAg.
Screening
Serological screening for HBV should be offered to pregnant women so that effective post-natal intervention can be offered to infected women to decrease the risk of mother-to-child transmission.
As many as 85 per cent of babies born to mothers who are positive for the hepatitis e antigen (eAg) will become HBsAg carriers and subsequently become chronic carriers, compared with 31 per cent of babies who are born to mothers who are eAg negative.
It has been estimated that chronic carriers of HBsAg are 22 times more likely to die from hepatocellular carcinoma or cirrhosis than non-carriers.
Mother-to-child transmission of the HBV is approximately 95 per cent preventable through administration of vaccine and immunoglobulin to the baby at birth. To prevent mother-to-child transmission, all pregnant women who are carriers of HBV need to be identifi ed. Because of the high proportion of cases of mother-to-child transmission that can be prevented through vaccination and immunization, the UK National Screening Committee
183 Perinatal infections causing long-term disease
C A S E H I S T O R Y
New developments
• In recent years a non-invasive method has been developed to diagnose and monitor fetal anaemia. This is done by using Doppler ultrasound to measure the velocity of blood fl ow in the fetal middle cerebral artery. Faster fl ow is indicative of fetal anaemia. This has improved the diagnosis and management of fetuses infected with parvovirus, as the main effect of this infection is anaemia.
• Antiretroviral HIV therapies have been developed and research has focused on which therapies are more appropriate for different groups of women.
• Hepatitis B vaccination programmes are being extended worldwide. In some countries such as Taiwan, this has already resulted in lower transmission rates and a reduction in childhood hepatocellular carcinoma.
• Further research is needed into the treatment of hepatitis C in pregnancy with antiviral agents, and into the most appropriate mode of delivery in women with hepatitis C.
The development of a hepatitis C vaccination would confer long-term health benefi ts.
Screening
Current recommendations are that pregnant women should not be offered routine screening for HCV. This is because there is a lack of evidence-based effective interventions for the treatment of HCV in pregnancy, and a lack of evidence about which interventions reduce vertical transmission of HCV from mother to child.
Clinical features
HCV is a major public health concern due to its long-term consequences on health. It is one of the major causes of liver cirrhosis, hepatocellular carcinoma and liver failure. Following initial infection, only 20 per cent of women will have hepatic symptoms, 80 per cent being asymptomatic. The majority of pregnant women with hepatitis C will not have reached the phase of having the chronic disease, and may well be unaware that they are infected.
Management
Testing for HCV in the UK involves detection of anti-HCV antibodies in serum with subsequent confi rmatory testing by PCR for the virus, if a positive result is obtained. Upon confi rmation of a positive test, a woman should be offered post-test counselling and referral to a hepatologist for management and treatment of her infection.
In non-pregnant adults, interferon and ribavirin can be used to treat hepatitis C infection, but these are contraindicated in pregnancy.
There is no strong evidence regarding mode of delivery in women with hepatitis C. Consensus groups therefore do not recommend elective Caesarean section for all women with hepatitis C, although it is recommended if the woman is also HIV positive.
Ms B is a 30-year-old shop assistant. This is her fi rst pregnancy and she attends for a routine anomaly scan at 20 weeks gestation. She has no family history or past medical history of note and has been well throughout her pregnancy.
On the ultrasound scan the fetus is seen to be small, approximately 18 weeks size. The ventricles in the brain measure 12 mm (the upper limit of normal is 10 mm).
There is a small amount of fetal ascites and some fetal skin oedema.
What are the possible causes?
These ultrasound fi ndings could be due to congenital infection, chromosomal abnormality in the fetus or genetic disorders. Various infections could cause these ultrasound abnormalities including syphilis, rubella, CMV and toxoplasmosis.
continued
Key points
• Infectious diseases contracted during pregnancy can have a serious impact on both the mother and the fetus.
• Infections can cause congenital abnormalities in the fetus (rubella, syphilis, toxoplasmosis, cytomegalovirus, chickenpox).
Some infections can be transmitted from mother to baby during pregnancy and affect the fetus in utero (parvovirus, syphilis).
• Some infections can be transmitted to the fetus around the time of delivery, and appropriate obstetric management can reduce the risk of transmission (HIV, hepatitis B, hepatitis C, herpes, group B streptococcus).
• For some infections screening programmes and effective interventions can improve the outcome for the mother and baby.
184 Perinatal infections
C A S E H I S T O R Y continued
Results
The initial booking blood sample did not have any antibodies for CMV. The sample sent on the day of her anomaly scan had CMV IgM, suggesting a recent infection. The PCR on the amniotic fl uid showed that it contained CMV.
These results together with the ultrasound fi ndings confi rm a diagnosis of congenital CMV infection.
What would you do next?
The results should be explained to Ms B. The likelihood of a very poor prognosis for the baby should be explained and termination of pregnancy offered. Throughout this she would need support and compassion. It should also be explained to her that since she would now be immune to CMV this would not happen again in a future pregnancy.
What would you do next?
The fi rst steps would be to take a careful history for symptoms suggestive of a viral illness or contact with illness.
The results of her routine screening blood tests taken at the booking visit should be checked. (These showed that she was immune to rubella and tested negative for syphilis.)
The virology lab should be asked whether they had retained the original sample and this should be checked for toxoplasmosis and cytomegalovirus antibodies. (She did not have any antibodies to these on her initial sample.) A further sample should be taken to be tested for toxoplasmosis and cytomegalovirus antibodies to see whether antibodies had developed. This would suggest recent infection.
She should be offered an amniocentesis to exclude chromosomal abnormalities. The amniotic fl uid should also be tested for toxoplasma and CMV.
Introduction ... 185
Fetal and maternal anatomy relevant to labour ... 186
The process of labour ... 191
Understanding the physiology of labour ... 194
Place of birth ... 195
Management of normal labour ... 196
Pain relief in labour ... 203
Abnormal labour ... 208
Labour in special circumstances ... 217
Induction of labour ... 219
Clinical risk management ... 223
O V E R V I E W
Labour can be defi ned as the process by which regular painful contractions bring about effacement and dilatation of the cervix and descent of the presenting part, ultimately leading to expulsion of the fetus and the placenta from the mother.
This gross oversimplifi cation hides a multitude of medical, social, cultural and ethical variables which combine together in a complex interplay and mean that labour and delivery can often have a long-lasting physical and emotional impact, which may be positive or negative. A doctor or midwife who manages labour must be aware of the normal anatomy and physiology of the mother and fetus, what distinguishes an abnormal from a normal labour, and when it is appropriate to intervene.
Alec McEwan
Introduction
Approximately 600 000 women give birth in the United Kingdom each year. Labour and delivery are both a physical and emotional challenge for the mother and represent a potentially hazardous journey for the fetus. There is a complex interaction between the ‘powers’ of the uterus (the contractions), the
‘passages’ of the birth canal (the bony pelvis and the soft tissues of the pelvic fl oor and perineum) and the ‘passenger’ (the fetus) which means that no two labours are ever quite the same. Contractions are necessary to promote dilatation of the uterine cervix and descent of the fetus, however during each one, the placenta is temporarily deprived of blood fl ow, and consequently the fetus of its oxygen supply.
Labour brings great joy and happiness to the majority of families, but maternal and fetal outcomes are not always good, and are frequently suboptimal.
Maternal death is rare in the Western world, but remains frequent in many countries that have less developed healthcare systems. Complications of labour account for a signifi cant proportion of maternal deaths in these countries, where childbirth is often unattended. This must not be confused with
‘natural childbirth’, a term used to describe a form
of care in labour that utilizes minimal technology and natural methods of pain relief. Women have widely different expectations of labour and delivery, influenced by previous experiences, friends and family, social, religious and cultural factors, the media and healthcare professionals. In the Western world, the expectation is usually that the outcome will be ‘normal’ and this is one reason why rates of litigation are so high following supposed intrapartum mismanagement. Maternal choice remains a high priority for policymakers, and also most midwives and obstetricians. Where a woman should give birth, who should care for her in labour, how she might deliver and with what kind of pain relief, are all key issues that are decided by a multitude of factors, including maternal choice. Natural childbirth may be sought by women who perceive that birth in the Western world has been ‘hijacked’ by modern medicine and modern doctors. Conversely, there is now a small but signifi cant minority of women who have the opposite philosophy: they have opted to avoid labour altogether and to elect for planned Caesarean section. Although this remains a contentious issue, many women have an increasing expectation that mode of delivery should be a matter of choice. The average Caesarean section rate in the UK is approximately 21 per cent,