Infections In Pregnancy and Neonates
Infections In Pregnancy and Neonates
Infections in pregnancy
Women of child-bearing age, whether pregnant or not, are susceptible to a wide range of infections. However, physiological changes associated with the pregnant state may alter both disease susceptibility and the clinical manifestations of infection in a pregnant woman. In addition, infectious agents may gain access to the developing foetus, or if maternal infection is acquired towards the end of pregnancy, to the neonate, with potentially devastating consequences. Recommendations for treatment of infection in a pregnant woman may differ, owing to unacceptable toxicities for the developing foetus.
Varicella (chickenpox) is often more severe in adults than in children. Data suggest that pregnant women with chickenpox are more likely to develop varicella pneumonia (the most common life-threatening complication) than if they were not pregnant. Pregnant women with chickenpox should therefore be carefully assessed for evidence of lung involvement and consideration given the need for intravenous aciclovir therapy.
Urinary tract infections are more common during pregnancy and can be asymptomatic. Urine screening for asymptomatic bacteria is therefore important, especially in early pregnancy, as severe kidney infection (pyelonephritis) may occur untreated.
Infection management in a pregnant woman must take into account the fact that certain agents are known to be potentially harmful to the developing foetus and should therefore be avoided. Almost all antiviral agents are not licenced for use in pregnancy, for obvious reasons—most of them interfere with DNA synthesis. There are however, two important exceptions. One would not hesitate to use aciclovir in a pregnant woman who has life-threatening varicella pneumonia. Antiretrovirals are also used in HIV-infected pregnant women to reduce the risk of transmission of infection from mother to baby.
A number of antibacterial drugs may be potentially toxic to developing foetuses and should be restricted during pregnancy (especially in the first trimester). These include trimethoprim, tetracycline, metronidazole, fluoroquinolones and aminoglycosides.
Maternal chronic virus infections
Mothers who are carriers of a bloodborne virus—i.e. HIV, hepatitis B or C virus (HBV, HCV)—may transmit the infection to their offspring. Such vertical transmission (i.e., mother-to-baby) may occur antenatally through the transplacental passage of the virus, perinatally, when the child is exposed to an infected birth canal and also to maternal or postnatal blood through breast milk. The rate of vertical transmission of HIV is around 20% and most infections occur perinatally. This can be reduced to <1 per cent with appropriate management—HIV carrier mothers should be given antiretroviral therapy during pregnancy, their infants should be given elective Cesarean section, and they should be advised not to breastfeed. The risk of transmission of HBV from mother to baby is >90% for HBeAg-positive mothers and 30% for anti-HBe-positive mothers.
Transmission may be interrupted by giving the baby adequate prophylaxis at birth—combined active (HBV) and passive (hepatitis B) immunizations for high-risk infants, active immunisation alone for low-risk infants. Vertical transmission of HCV is unusual-approximately 4 percent of infants of carrier mothers are infected. There is currently no proven form of prophylaxis to reduce this risk. Note that correct management of HIV-and HBV-infected mothers requires knowledge of who they are. Universal antennatal screening for evidence of maternal HIV and HBV infection is therefore an essential part of any policy to prevent transmission of these infections. This is now the official policy in the United Kingdom.
A particular concern for any pregnant woman with an infectious disease is whether or not this will affect her developing child. The foetus is in a protected environment within the uterus, but if the organism is present in the maternal bloodstream, it will have access to and may cross the placenta. Depending on the stage of gestation and the nature of the particular organism, this may or may not have serious consequences. It is said that a baby born infected with an organism is congenitally infected.
In addition to the specific infections listed below that may cross the placenta, there is also a general increased risk of spontaneous abortion (especially in early stages of pregnancy) with a range of infections (mainly viral) that cause fever and inflammatory reactions (e.g. influenza, measles).
Congenital cytomegalovirus (CMV) infection is the most common congenital infection occurring in 1 in 300 live births. Fortunately, the vast majority (80–85%) of CMV-infected infants are not adversely affected (i.e. they are normal at birth) and develop normally. Five to 10% of infants are severely damaged, amounting to ~300 such infants per year in the United Kingdom. They have multiple developmental abnormalities, and many do not survive more than one year. The remaining 5–10% of CMV-infected infants are normal at birth, but are shown to have suffered some damage as they develop (e.g. uni-or bilateral nerve deafness). The outcome of congenital CMV infection is not dependent on either the nature of the maternal infection (i.e. primary or secondary CMV infection) or the stage of pregnancy at which the foetus is infected. There are currently no effective prevention strategies Congenital CMV infection.
In contrast to CMV, the effects of congenital rubella infection are highly dependent on maternal infection. Infection during the first 12 weeks carries a very high risk of congenital rubella syndrome (CRS), with multiple abnormalities affecting the eyes, the central nervous system and the heart. Breast infection after 18 weeks of pregnancy carries virtually no risk of foetal damage. CRS is preventable through universal childhood rubella vaccination (as part of MMR). This prevents the circulation of the virus within the community and thus eliminates the risk that a susceptible pregnant woman will come into contact with the virus. Note that maternal infection with parvovirus B19, which may be clinically very similar to maternal rubella, does not result in permanent congenital damage.
It may, however, cause hydrops fetalis and there is an increased risk of intrauterine death/spontaneous miscarriage, but if the pregnancy survives, the child will be normal. If a pregnant woman develops chickenpox in the first 20 weeks of pregnancy, there is a 1% risk that her baby will have congenital varicella, the main features of which are developmental limb bud failure and areas of severe skin scarring. Infection with maternal toxoplasmosis may cross the placenta. The risk of transplacental transmission of this organism increases during pregnancy, but the earlier this occurs, the greater the risk of serious foetal brain damage.
Maternal syphilis (due to Treponema pallidum) may also cause congenital infection. Congenital syphilis affects many parts of the body and a range of clinical features usually occur between the ages of 5 and 15 years. Routine serological screening during pregnancy and treatment with penicillin has made this a very rare condition in the developed world.
Acute infections in the neonatal period
Human immune systems are not fully mature at birth. Neonates are largely protected from infection by transplacental maternal antibodies, but in the absence of such antibodies, life-threatening neonate infections may otherwise be trivial. Bacterial infections may be severe in the early neonatal period especially in premature and/or low birth weight neonates. Septicemia and neonatal meningitis are mainly caused by Streptococci B (Streptococcus agalactiae) and Escherichia coli. These bacteria are usually acquired from the mother’s birth canal during delivery or due to premature rupture of the membrane, which is complicated by chorioamnionitis. Mothers who are known to be vaginal carriers of group B streptococci (GBS) should be given antibiotics during labor to reduce the risk of early-onset GBS infection. Some countries have developed screening programmes for GBS carriage during pregnancy.
A rare, but potentially serious, bacterial infection during pregnancy is listeriosis (Listeria monocytogenes). This is a food-borne illness that can cause either septic abortion, or a chorioamnionitis with early-onset neonatal septicemia or meningitis. Staphylococcus aureus is a common cause of minor neonatal skin infections, but can also cause more severe soft tissue infections and sepsis. Mothers with chickenpox in late pregnancy may infect their fetus/neonate without having passed on protective antibodies. Neonatal varicella is a feared disease, with a high mortality. Babies of mothers with varicella should be given varicella-zoster immunoglobulin at birth, and also prophylactic acyclovir for 14 days.
Neonatal herpes infection is also a potentially devastating disease. Infection is acquired from an infected birth canal, in mothers undergoing a primary genital herpes simplex infection late in pregnancy. The virus is disseminated through the bloodstream, and many babies die of herpes encephalitis or through involvement of other internal organs. Survivors may be left with severe brain damage. Fortunately, neonatal herpes is rare.
Ophthalmia neonatorum is an acute purulent conjunctivitis in neonates caused by Neisseria gonorrhoeae or Chlamydia trachomatis . These infections are acquired from the mother’s genital tract, during birth. C. trachomatis can also cause neonatal pneumonia.
Premature and low-birthweight neonates on neonatal units are particularly vulnerable to many other infections, particularly as their immature immune system is further compromised by thin, fragile skin, and the presence of invasive medical devices that are required to support their care. In addition to the infections already mentioned, neonatal sepsis with coagulase-negative staphylococci (related to venous catheters), coliforms, pseudomonads and Candida, are commonly seen.