Screening for infectious disease in pregnancy

Key messages from UK National Screening Committee about the NHS Infectious Diseases in Pregnancy Screening (IDPS) Programme:

• as part of this programme, all pregnant women in England should be routinely offered screening for hepatitis B, HIV, syphilis and susceptibility to rubella, early in pregnancy
• the programme aims to identify women with hepatitis B, HIV and syphilis in pregnancy, and ensure that strategies are put in place to prevent mother-to-child transmission, as well as safeguard the woman's own health. The programme also aims to identify women for whom MMR vaccination could protect future pregnancies
• all women who have positive screen results for HIV, hepatitis B, syphilis should be referred to a relevant specialist for clinical assessment and appropriate management and care. Women who are susceptible to rubella infection should be offered postnatal MMR, ideally prior to discharge from hospital.
• babies born to mothers with hepatitis B are at risk of acquiring the infection and should be offered postnatal immunisation to reduce the risk of transmission.

Screening for Infectious Diseases in Pregnancy

• screening for Infectious Diseases in Pregnancy
  • the offer
    • screening for the four infections should be offered to all pregnant women early in pregnancy
    • screening should be re-offered to those women who decline the initial offer and screening should be available on request during the pregnancy should a woman consider herself to be at risk
    • screening can be offered to those women who present unbooked in labour, or postnatally
  • the diseases and potential benefit of screening
• if the offer is accepted blood samples should be ideally taken at the earliest opportunity:
  
  
  • i) Human Immunodeficiency Virus (HIV)
    • HIV is a retrovirus that infects and damages T-lymphocytes, resulting in immune suppression that may lead to acquired immune deficiency syndrome (AIDS)
    • HIV is transmitted through: sexual contact contact with contaminated blood products mother to child transmission during pregnancy or delivery or breast feeding
    • screening for HIV in pregnancy identifies HIV-positive women so that they can be offered appropriate interventions to reduce the risk of mother-to-child transmission of infection, as well as to safeguard their own health
    • Mother-to-child transmission can be reduced to less than 1% with optimal management, which includes antiretroviral therapy, appropriate management of delivery and avoidance of breastfeeding
    • the objectives of the screening programme are to: identify all HIV positive women and those with positive test results and ensure the rapid referral of all HIV positive women for assessment and management within a multi-disciplinary team.
    • DH states;
      • All women to be offered and recommended an HIV test as part of antenatal care
      • The uptake of antenatal HIV testing should be 90% or higher with 80% of HIV infected pregnant women being identified and offered advice and treatment during antenatal care
        
        
  • ii) Hepatitis B Virus (HBV)
    • Hepatitis B Virus (HBV) is an infectious disease that affects the liver and which can result in both acute and persistent infection. Chronic infection may result in cirrhosis of the liver or liver cancer
    • HBV is transmitted through: sexual contact contaminated blood e.g. needle sharing mother to child transmission
    • Babies born to mothers with hepatitis B are at risk of acquiring the infection and should be offered postnatal immunisation, within 24 hours of delivery, and at 1, 2 and 12 months, to reduce this risk. A full course of vaccination in the first year of life is effective in reducing the risk of transmission to the baby
    • In babies born to women with a higher risk of transmission, the addition of Hepatitis B Specific Immune Globulin (HBIG) can reduce the risk further
    • The objectives of the screening programme are to ensure:
      • that all hepatitis B positive women are identified;
      • all hepatitis B positive women are referred for assessment and management by an appropriate specialist (eg a hepatologist / gastroenterologist / infectious diseases specialist) within 6 weeks of the screening test result being received by maternity services; and that the infant vaccination schedule is offered for their babies, the first dose is administered within 24 hours of delivery and arrangements for completion of the schedule are initiated
        
        
  • iii) Syphilis
    • syphilis is an infectious disease caused by the Treponema pallidum bacterium. Syphilis is transmitted through: sexual contact; and mother to child transmission
    • maternal syphilis infection can result in a range of adverse pregnancy and neonatal outcomes, including miscarriage, stillbirth, hydrops and low birth weight. If left untreated, congenital syphilis can result in physical and neurological impairments
    • acquired and congenital syphilis infection is staged according to the time from acquisition of the primary infection. The risk of transmission from mother to baby declines as maternal syphilis infection progresses
    • screening for syphilis in pregnancy is to identify women with active syphilis and offer treatment for their own infection and to reduce the risks of the baby developing congenital syphilis
    • the objectives of the screening programme are to: identify all women with positive syphilis screening test results early in pregnancy; and ensure their rapid assessment by an appropriate specialist, eg a Genitourinary Medicine (GUM) within a multi-disciplinary environment
    • screening in pregnancy aims to identify women with an infection and offer treatment which will reduce the risks of the baby developing congenital syphilis. If the pregnant woman has an untreated syphilis infection, the fetal loss rate is approximately 50%. Babies that survive suffer considerable morbidity including: naso-facial hypoplasia, blindness, deafness, bone abnormalities etc. Congenital syphilis is transmitted via the placenta.
    • the screening tests have an accuracy of over 99%. Positive or equivocal results require urgent referral to genitourinary medicine for antibiotic treatment and discussion regarding the risks to the baby
      
      
  • iv) Rubella susceptibility
    • Rubella is a mild infection caused by the rubella virus. It is often asymptomatic, but may present with a rash
    • if a woman is infected in the first trimester it can have serious consequences for the baby's health for example congenital abnormalities such as heart defects, cataracts, intrauterine growth restriction, central nervous system defects and deafness
    • screening does not detect rubella infection in pregnancy and any woman presenting with a rash or who is exposed to others with a rash-like illness should be investigated in accordance with Health Protection Agency Guidelines for Managing Rash Illness in Pregnancy
    • the purpose is to reduce the risk of infection in a subsequent pregnancy. Screening for rubella susceptibility should be offered to all pregnant women to identify those who are eligible for the two dose post partum MMR vaccination schedule which will reduce the risk of infection in future pregnancies
    • the objectives of the screening programme are to ensure that:
      • all women with tests indicating susceptibility to rubella infection (<10 IU/ml) are identified
      • postnatal MMR vaccination is offered to susceptible women,
      • MMR is administered prior to discharge from maternity services to those who accept and that the GP is contacted regarding a second dose of MMR
      • Women should be advised not to conceive within one month of vaccination. MMR and Anti D can be given at the same time but in opposite arms. Anti D should be given in the arm (i.e. deltoid muscle) as opposed to the buttock (gluteal muscle) for better absorption.
    • screening in pregnancy is to identify women who require vaccination postpartum in order to prevent congenital rubella in subsequent pregnancies. Congenital rubella can cause multiple problems including deafness, heart and eye defects. In the first 8 - 10 weeks of pregnancy infection results in severe fetal damage in up to 90% of cases. After this period, the risk of damage is lower and likely to involve hearing impairment. Rubella defects are rare after 16 weeks gestation. An antibody level of less than 10iu/ml is IgG negative (non immune).
    • The Health Protection Agency (HPA) and Royal College of Obstetricians and Gynaecologists (RCOG) recommend that all rashes in pregnancy should be investigated

Further Information, standards and training resources are available on the following web link: http://infectiousdiseases.screening.nhs.uk/

The UK NSC's advice on the following infections, not currently recommended, is listed below:

• Cytomegalovirus
  • the UK NSC does not recommend screening for CMV in pregnancy because:
    • most babies with CMV develop normally and available tests are unable to distinguish between pregnancies which would seriously affect the infant and those which would not
    • the diagnostic pathway in pregnancy is complicated and unlikely to be effective
    • no interventions are currently available to reduce the risk of mother to child transmission or to reduce the risk of adverse outcomes in congenitally infected infants
      
      
• Hepatitis C virus
  • The UK NSC does not recommend screening for hepatitis C in pregnancy because:
    • the mother-to-child transmission rate is low (approximately 3 - 5%)
    • the natural history of vertically acquired hepatitis C is not well understood o current tests would result in a large number of women who are not infected being recalled for a confirmatory test
    • there are no interventions to reduce the risk of mother-to-child transmission e.g. anti-viral treatment, caesarean section
      
      
• Toxoplasmosis
  • The UK NSC does not recommend screening for toxoplasmosis in pregnancy because:
    • for sero-negative women undergoing repeated serological testing, the screen false positive rate would be high and the effect of congenital toxoplasmosis on developmental and visual impairment in later childhood is unknown
    • there is no clear evidence that prenatal treatment reduces the risk of mother to child transmission of toxoplasmosis or the clinical manifestations in infected children
    • a policy of primary prevention is recommended in the UK
    • pregnant women should be informed of primary prevention measures to avoid toxoplasmosis infection, such as:
      • washing hands before handling food
      • thoroughly washing all fruit and vegetables, including ready-prepared salads, before eating
      • thoroughly cooking raw meats and ready-prepared chilled meals
      • wearing gloves and thoroughly washing hands after handling soil and gardening
      • avoiding cat faeces in cat litter or in soil
• Group B streptococcus
  • The UK NSC does not recommend screening for GBS because
    • the advantages of screening and treating with intravenous antibiotics during labour have not been demonstrated in the UK
    • the Royal College of Obstetricians and Gynaecologists (RCOG) has published a guideline for professionals and information for the public http://www.rcog.org.uk/womens-health/clinical-guidance/preventing-group-b-streptococcus-gbs-infection-newborn-babies
  • NICE state that pregnant women should not be offered routine antenatal screening for group B streptococcus because evidence of its clinical and cost effectiveness remains uncertain

Further information on the UK NSC's policy positions can be viewed here:

• http://infectiousdiseases.screening.nhs.uk/

References:

1. NICE. Antenatal care for uncomplicated pregnancies. Clinical guideline CG62. Published: 26 March 2008 Last updated: 04 February 2019
2. http://infectiousdiseases.screening.nhs.uk/