Prenatal Infection Prevention

Prenatal infections include bacterial or viral illnesses that can be passed from a mother to her baby during pregnancy or during the delivery process.

Mother to baby transmission of infection can occur in utero (congenital), at and around the time of delivery (perinatal) or subsequently (postnatal) as illustrated by transmission of organisms by breastfeeding.

Maternal infections spread to the embryo and foetus by: * Ascending infection from the upper vagina via the uterine cervix to the amniotic fluid or by * Hematogenous spread as a result of maternal viremia, bacteremia or parasitemia.

When infections are acquired by ascending route, microorganisms, more commonly can cause inflammatory changes (chorioamnionitis) in the amnion and chorion (membranes which make up the gestational sac) and may lead to premature rupture of these membranes and preterm delivery. Often, fetal pneumonia will occur as a result of the entrance of the infected amniotic fluid into the lungs.

When infections are acquired by ascending route, microorganisms, more commonly can cause inflammatory changes (chorioamnionitis) in the amnion and chorion (membranes which make up the gestational sac) and may lead to premature rupture of these membranes and preterm delivery. Often, fetal pneumonia will occur as a result of the entrance of the infected amniotic fluid into the lungs.

If infections spread hematogenously (by blood), more commonly viral infections, the placenta is often infected resulting in deciduitis and villitis (inflammation of the two important parts of the placenta vital to foetal survival).

Infections during pregnancy are one of the major causes of foetal and neonatal morbidity and mortality.

Although congenital anomalies are rare, in utero infections may lead to embryonic or foetal death. Asymptomatic infections at birth may have late clinical manifestations that become evident only later in life, but mostly in the first years of childhood..

The foetus may be affected not only by the direct transmission of the agent, but also indirectly by the consequences of maternal infection, such as preterm birth or foetal growth restriction (FGR). In utero transmission occurs variably depending on the infectious agent, gestational age at the time of transmission, and the immune status of the mother. In general, primary infections during pregnancy are substantially more damaging than re-infections or reactivations of infection. Likewise, infections acquired at an earlier gestational age tend to lead to more serious infections.

Examples of Prenatal Infections

Some examples of prenatal infections include:

  • Treponema pallidum (Syphilis)
    • Syphilis is a disease caused by the bacterium Treponema pallidum, which is transmitted sexually during vaginal, anal or oral sex. Syphilis is easy to treat with antibiotics in the early stages of the disease
    • Congenital syphilis can be acquired from an infected mother via transplacental transmission of T. pallidum at any time during pregnancy or at delivery.
    • Transmission to the fetus can occur at any stage of disease. The rate is highest (60% to 100%) during primary and secondary syphilis decreasing to approximately 40% during early latent infection and 8% during late latent infection
  • Human immunodeficiency virus (AIDS)
    • Human Immunodeficiency virus (HIV) is a retrovirus that infects helper T cells of the immune system, causing a progressive reduction in their number, and eventually Acquired Immunodeficiency Syndrome (AIDS).
    • There are several factors associated with the risk of vertical transmission. These factors can be divided into those associated with maternal, obstetric or postnatal
    • Maternal
      • advanced maternal HIV disease,
      • Maternal antenatal CD4 counts less than 200 cells/mm3 and
      • high maternal plasma viral loads
    • Obstetric risk
      • vaginal delivery
      • duration of membrane rupture
      • chorioamnionitis and Preterm delivery.
    • Postnatal
      • Breastfeeding is associated with a two-fold increase in the rate of HIV transmission
  • Rubella virus
    • Rubella virus is the first virus documented to be a teratogen, causing severe congenital anomalies.
    • It is a contagious disease transmitted via the respiratory system secretions from the nose or throat. Viremia occurs 5-7 days after the contact period during which the virus may be transmitted from the mother to the fetus by hematogenous trans-placental spread
    • CONGENITAL RUBELLA SYNDROME (CRS) - CRS is characterized by:
      • Cardiac defects
      • Cataracts
      • Hearing impairment
      • Developmental delay
      • “blueberry muffin” skin lesions
      • Pneumonitis
      • Myocarditis
      • Disturbances of bone growth
      • Microcephaly
    • The incidence of these congenital anomalies depends on the gestational age at which infection occurred:
      • 90% during the first 8 weeks,
      • 50% from 9-12 weeks and
      • 15% between 13 and 16 weeks.
      • Risk of fetal damage falls steeply after the first trimester and is negligible after 16 weeks.
    • CONGENITAL DEFECTS ACCORDING TO THE TIME OF INFECTION
Gestational Period Congential Anomaly Risk (%)        
First trimester Ocular, cardiovascular, CNS, Hearing impariment, IUGR, 38-100        
Second trimester Hearing impariment, retinopathy, microcephaly, mental retardation 4 - 60   Third trimester IUGR 0-18
  • The affected infants continue shedding virus for 6-12 months after birth
  • Plasmodium falciparum (Malaria)
    • Plasmodia species are the parasites responsible for Malaria.
    • The parasite is transmitted by Anopheles mosquitoes. Warm climates with high humidity and abundant rain create favorable conditions for the growth and development of mosquitoes
    • Malaria infection during pregnancy results in a wide range of adverse consequences for the pregnant woman, the developing fetus and the newborn infant. HIV infection can further reduce immunity to malaria during pregnancy
  • Hepatitis B virus
    • Hepatitis B virus (HBV) is a blood borne virus that is transmitted by percutaneous or mucosal exposure to blood or body fluids.
    • For infants and children, the primary source of HBV infection is transmission from infected mothers. After birth the risk of infection continues by transmission from infected household contacts.
    • The major sources of transmission among adults are sexual contacts and percutaneous exposures to blood.
    • Transmission from mother to the neonate most often occurs at the time of delivery.
    • In utero infection occurs rarely. Breast milk is known to contain the virus, but breastfeeding has not been shown to increase the risk of acquiring HBV.
  • Trypanosoma cruzi (Chagas disease)
    • Chagas disease is caused by the protozoan parasite Trypanosoma cruzi. It is a zoonotic disease that can be transmitted to humans when infected feces from blood-sucking triatomine insects are inoculated into the bite wound or into mucous membranes such as the conjunctivae
    • Congenital infection occurs in up to 15% of pregnancies in infected women.
    • Congenital infection may be asymptomatic or symptomatic in the newborn; when symptomatic it can cause fever, petechiae, enlarged liver, enlarged spleen and/or anemia, and microcephaly
  • Group B streptococci
    • Group B Streptococcus (GBS), also known as S agalactiae, is an encapsulated gram-positive bacterium that is a common inhabitant of the human gastrointestinal and genitourinary tracts.
    • Intrauterine infection of the fetus results from ascending spread of GBS from the vagina or during passage through the birth canal, of a colonized woman who is typically asymptomatic. However, transmission of GBS from mother to child primarily occurs after the onset of labor or membrane rupture. Infants can become ill after passage through a colonized birth canal, via aspiration of contaminated amniotic fluid, via ascending infection through ruptured membranes, or very rarely when GBS is transmitted via the maternal bloodstream
  • Varicella zoster virus (Chickenpox)
    • Varicella (also known as Chickenpox), is a highly contagious disease of childhood caused by Varicella Zoster Virus (VZV). After an average incubation period of 14 to 16 days (range 10-20 days) following primary infection, lesions develop in three or more successive waves for 3 to 7 days.
    • Lesions progress through macular, papular, Vesicular, and pustular stages. Eventually scabs form, which usually heal without scarring unless secondary bacterial infection occurs.
    • Skin lesions appear on trunk, face, scalp and extremities, with greatest concentration on trunk. Virus is spread by the airborne route from the skin lesions and oropharynx of infected individuals.
    • When primary infection with VZV occurs during pregnancy, the consequences for both the mother and the fetus must be considered. Chickenpox in pregnancy may be associated with severe maternal disease, fetal death and rarely, (during the first two trimesters), with congenital varicella syndrome. Maternal infection around term carries the risk of serious neonatal disease
  • Herpes simplex virus
    • HSV-1 : Herpes simplex virus type 1 is very common, in fact it is more common than HSV-2 infection
    • HSV-2 : The majority of cases of genital herpes are caused by HSV-2 and nearly all are sexually acquired. Recurrent lesions are common. Most infections are asymptomatic.
    • However, sexual transmission of HSV-1 is becoming increasingly common, especially through oral-genital contact.
    • In some populations, up to 50% of first-episode cases of genital herpes may be caused by HSV-1 Recurrences and subclinical viral shedding are much less frequent for HSV-1 than HSV-2, therefore HSV-2 is a much more common cause of recurrent genital herpes
  • Neisseria gonorrhoeae (Gonorhea)
    • Neisseria gonorrhoeae is a bacterium that infects humans only, and is transmitted by intimate sexual contact.
    • Newborns infants can also acquire gonococcal infections in their eyes if they are delivered vaginally while their mothers have a cervical gonococcal infection
  • Chlamydia trachomatis
    • Chlamydia trachomatis, is a bacterium that can live and reproduce inside human cells without actually damaging them, and can cause prolonged infections with minimal or no symptoms. 90% of infected women and about 80% of infected men have no symptoms. *
  • Toxoplasma gondii
    • Toxoplasma gondii is an intracellular protozoan parasite that infects up to a third of the world’s population.
    • Infection is acquired primarily by ingestion or handling of undercooked or raw meat (especially pork, lamb and wild game meat) containing tissue cysts or by ingestion of food or water contaminated with oocysts excreted in the faeces of infected cats.
    • Primary infection is usually asymptomatic or has mild, non-specific, symptoms. Some individuals develop cervical lymphadenopathy or ocular disease
  • Cytomegalovirus
    • Human CMV is a DNA virus of the herpes virus group that infects cells and causes them to become enlarged. CMV spreads through human contact, by the infected person’s saliva, blood, urine, semen, cervical/vaginal secretions or breast milk. CMV survives on fomites, including diapers, toys, and the hands
  • Parvovirus
    • Parvovirus B19, (also known as erythrovirus B19) is a small that causes erythema infectiosum (fifth diseases) among children, arthropathy in normal adults and transient aplastic anemias in patients with increased erythropoiesis, such as a child with sickle cell anemia
  • Hepatitis C virus
    • The hepatitis C virus (HCV) is an RNA virus with at least six different genotypes. HCV is primarily parenterally transmitted; in health care settings via needle- sticks, among intravenous drug users through the sharing of needles, or via blood transfusion where blood is not adequately screened. . Chronic infections may persist for up to 20 years before the onset of sequellae, including cirrohosis or hepatocellular carcinoma
  • Listeria monocytogenes
    • Listeriosis is caused by ingesting food contaminated with the gram-positive motile
    • This bacterium is unusual in that it grows between 4oC and 37oC.
    • Because of this property, it can grow on foods that are stored in refrigerators, and unless these foods have been thoroughly cooked, the consumer may be exposed to a large dose of the bacterium
  • ZIKA
    • Zika virus disease is caused by a virus transmitted primarily by Aedes mosquitoes, which bite during the day.
    • Symptoms are generally mild and include fever, rash, conjunctivitis, muscle and joint pain, malaise or headache. Symptoms typically last for 2–7 days. Most people with Zika virus infection do not develop symptoms.
    • Zika virus infection during pregnancy can cause infants to be born with microcephaly and other congenital malformations, known as congenital Zika syndrome. Infection with Zika virus is also associated with other complications of pregnancy including preterm birth and miscarriage.

Prevention

Systematic Screening Maternal infections that could affect the fetus can be diagnosed when resources are available. Because in many circumstances, even when first acquired, infections are asymptomatic, diagnosis depends on effective screening methods. For some infections, the cost benefit value of routine screening during pregnancy is lacking. In many areas, the most specific and sensitive tests are not readily available. If maternal infection is confirmed, transmission in utero is often difficult to confirm. When available, pre-conceptional and antenatal screenings of the mother, and neonatal screening of the infant, play a major role in early diagnosis and timely treatment.

Education Prevention of maternal primary infection by modifying habits that may increase contact with agents of communicable diseases is a relevant medical intervention. (See table of General Preventive Measures that women should follow to avoid infection during pregnancy). Additionally, educating mothers about pre-conceptional and antenatal screenings and prevention strategies in the case of maternal infection is critical to ensuring that missed opportunities for prevention do not occur. Maternal immunity is transmitted passively to the fetus for those agents for whom she has developed antibodies. Vaccines should be administered in the pre-conceptional period. If vaccines are administered during childhood, protection is conferred through the childbearing years against:

  • Poliomyelitis
  • Hepatitis B
  • Measles
  • Tetanus
  • Mumps
  • Rubella
  • Varicella zoster (not yet confirmed)

During pregnancy women should receive a vaccine only when: * It is unlikely to cause harm, * The risk of exposure is high, and * The infection would pose a significant risk to the mother or * fetus/neonate or both, such as:

  • Influenza
  • Diphtheria
  • Tetanus and
  • Hepatitis B

VIDEOS

How to prevent infectino during pregnancy
Infections that can affect Pregnancy and how to avoid them
Prenatal Infection Tips From A-Z

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