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Extracted from Survival Guide to Midwifery, 2nd Edition (2012) Diane M. Fraser and Margaret A. Cooper, Oxford; Churchill Livingstone: 2012. Courtesy Elsevier, and Myles Textbook for Midwives 15th Edition. Diane M. Fraser, Margaret A. Cooper (Eds). London; Churchill Livingstone: 2009. Courtesy Elsevier.
Newborns can acquire infections via a number of routes - from the placenta (transplacental infection), from amniotic fluid, from their passage through the birth canal, and from carers' hands, contaminated objects or droplet infection after birth.
Newborns are immunodeficient and prone to a higher incidence of infection. Preterm babies are even more vulnerable, as they have less well-developed defence mechanisms at birth (transfer of IgG occurs after 32 weeks' gestation. They are also more likely to experience invasive procedures.
At birth the baby has some immune protection from the mother, from maternal antibodies developed in response to exposure to antigens. (For this reason, it is recommended that women have a pertussis immunisation booster ideally at 20 weeks but by 32 weeks' gestation).
Breastfeeding increases the baby's immune protection through the transmission of IgA in breast milk. During the early weeks of life the baby also has deficiencies in both the quantity and quality of neutrophils.
Individual risk factors for infection
The overall aim of management of neonatal infections is to provide prompt and effective treatment that reduces the risk of sepsis. Good management includes:
Some specific neonatal infections are described below:
Group B streptococcus
The leading cause of serious neonatal infection in the UK is Group B streptococcus (GBS). Early onset (when symptoms develop within the first 5 days of life) suggests that the infection started in utero. In the USA, pregnant women are screened in the third trimester for GBS and are treated prophylactically with intrapartum penicillin.
WHO figures estimate that maternal syphilis affects 1 million pregnancies each year, with 460,000 resulting in abortion or perinatal death. In the UK, antenatal screening for syphilis is routine and the incidence of infectious syphilis is low. Vertical transmission may occur at any time during pregnancy in untreated early syphilis and the rate of vertical transmission in untreated women is 70-100 per cent for primary syphilis, but the risk of transmission diminishes as maternal syphilis advances. The UK prevalence of congenital syphilis is very low, but is associated with serious neurological, developmental and musculoskeletal sequelae; the prognosis is considered poor if symptoms present in the first few weeks of life. Signs in symptomatic infants may be subtle and non-specific, but characteristically include prematurity, low birthweight, hepatomegaly with or without splenomegaly, and failure to thrive. Treatment is usually with penicillin.
Herpes simplex virus (HSV)
Neonatal herpes is a severe systemic viral infection with high morbidity and mortality. The incidence in the UK is about 1.65 in 100,000 births and can be caused by either HSV-1 or HSV-2. Women who have had herpes prior to pregnancy will have developed antibodies to the virus, and the fetus will have passive immunity. The greatest risk to the fetus is therefore if the woman acquires a primary infection in late pregnancy. Congenital HSV infection can cause severe congenital abnormalities. About 70 per cent of cases of neonatal HSV are caused by HSV-2 and result from contact with maternal genital secretions during delivery; or from an ascending infection following rupture of the membranes.
Human immunodeficiency virus (HIV)
As the incidence of HIV infection in women increases, so does the problem of vertical transmission. Worldwide, millions of children are infected, primarily through mother-to-child transmission during pregnancy or breastfeeding. HIV-positive women should be offered an elective caesarean section as this is an effective way of reducing vertical transmission among women not taking antiretroviral drugs. In a woman with a low viral load, it is unclear whether caesarean section is more or less effective than vaginal birth. Breastfeeding contributes significantly to vertical transmission of HIV and should be avoided.
See also HIV, Ophthalmia neonatorum, Rubella, Toxoplasmosis, and Varicella Zoster
NICE (2014) Quality standard 75. Neonatal infection. https://www.nice.org.uk/guidance/qs75
NICE (2012). Clinical guideline 149. Neonatal infection: antibiotics for prevention and treatment. https://www.nice.org.uk/guidance/cg149