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By Vincent T. Brandeis, M.D.
Added 04/30/2010
Infectious diseases exert a broad spectrum of effects on reproduction. Acute infections may not manifest as reproductive consequences until after months or years. Human reproduction itself provides unique opportunities for the spread of infectious agents, as in the mechanics alone of sexual intercourse, pregnancy, delivery and breastfeeding, which breech physical barriers that normally protect against transmission of infections.
The most serious damage is on fertility, embryogenesis and fetal development. Infections can also be a major factor in preterm delivery, and may be contribute more subtly to miscarriage risk and impaired fetal growth.
Understanding the impact of infectious diseases on reproductive outcomes enables the physician to better evaluate and counsel patients. It also underscores the need for greater vigilance about pre-conception infectious disease screening.
Infections can interrupt reproduction at virtually any stage, starting with the development of egg cells and sperm, to the viability and ultimate survival of the newborn.
- The male and female reproductive tracts, egg cells and sperm, and the developing fetus are all particularly susceptible to infections.
- The reproductive organs themselves can be damaged directly by sexually transmitted diseases or by organisms transmitted through other routes.
- Reproductive tissues are particularly susceptible to obstruction or destruction by inflammation that results even from mild infection.
- The physiology of pregnancy induces a state of immune compromise that amplifies the pregnant woman’s vulnerability to infection.
Infections can be bacterial, viral, fungal or parasitic – and they can all affect reproductive health. An easy approach is to consider the stage of reproduction at which a particular infection exerts its effect.
The most common infections are Chlamydia, gonorrhea, group-B Strep, and genital TV (bacterial); mumps, TORCH viruses, hepatitis-B, human papilloma virus, herpes, and HIV (viral); and toxoplasmosis and trichomonas (parasitic).
Bacterial infections
Chlamydia trachomatis – This affects the male and female reproductive organs, pregnant women and fetuses. It is the
most common cause of tubal disease. It causes inflammation and damage to the inner lining of the fallopian tubes, often
leading to blockage. Even subclinical (asymptomatic) chlamydial infection can damage fertility and markedly increases the
risk for ectopic pregnancy. It accounts for half of all cases of tubal pregnancies worldwide. Chlamydia effect on male
infertility is so far merely an association - it can cause urethritis, and if left untreated, can cause orchitis (inflammation of the
testes); it also affects sperm count. In pregnant women, it is associated with as much as 50% increased risk for pre-term
birth due to premature rupture of infected membranes. Women who have active Chlamydia at delivery have a 50-75% risk of
transmitting the infection to the newborn, manifested as conjunctivitis or pneumonitis.
Gonorrhea - In males, it is thought to cause infertility because of resulting orchitis, which affects sperm development. In
women, it produces similar effects on the fallopian tubes as Chlamydia, leading to infertility, subfertility and ectopic
pregnancies, and as much as a 6-fold higher risk for pre-term births and substantially lower birth weight even if fetal growth
is not reduced. The mother-to-child transmission rate during delivery is 30-50%, also mostly manifested as conjunctivitis.
Bacterial vaginosis (BV) – This is a non-specific overgrowth in the vagina of microbes including Gardnerella, accompanied
by a decrease in normally prevalent Lactobacillus. In the United States 9-50% of pregnant women have BV, especially among
minority or low-income women, lwith a 2-fold increased risk for pre-term birth due to the infection of the fetal membranes
and amniotic fluid, and premature rupture of membranes.
Group-B Streptococcus (GBS) – Maternal infection is asymptomatic, but before 1990, GBS was the leading cause of
neonatal sepsis in the United States. Affected newborns develop pneumonia, meningitis, sepsis and death in 50% of babies.
In 2002, the Centers for Disease Control issued guidelines for screening and prophylactic antibiotic treatment of infected
pregnant women which dramatically reduced the incidence of early neonatal GBS sequelae.
Viral infections
Mumps caused by Paramyxovirus is a significant risk factor only in males. When contracted as an adult, it causes orchitis in
20-30% of patients, of which 10-30% will have both testes affected by inflammation (orchitis), which in half of patients will
result in testicular atrophy. A 2006 review showed that 13% of men with one affected testis were infertile compared to as
many as 30-87% if both testes are affected.
HIV decreases sperm count and increases abnormal sperm, causing progressively decreased fertility as the disease
advances. In Africa, where AIDS is endemic, HIV appears to reduce female fertility by 16-26%, manifested by longer periods
of involuntary childlessness. Advanced disease can produce hormonal dysfunction generally associated with ovarian failure.
Neonates born to HIV-positive women have a 15-25% chance of infection during delivery if the mother has not received antiretroviral
prophylaxis, so in advanced countries, the neonatal infection rate is less than 2%. There is a 15% risk of HIV
transmission in infants who are breastfed for a year. Supplemental feeding increases the risk of transmission, so in poor
countries, WHO recommends exclusive breastfeeding for six months only.
A number of viruses are associated with birth defects.
TORCH infections all have potentially devastating effects to the fetus particularly when the mother acquires them in the
third to 16th weeks of pregnancy, when the organs are developing. TORCH is the acronym for toxoplasmosis, other
(syphilis, measles virus, parvovirus B19), rubella, cytomegalovirus (CMV) and herpes (though toxoplasmosis and
syphilis are not viruses). Their common effects include restricted fetal growth, preterm delivery, neonatal jaundice,
microcephaly, mental retardation and cataracts.
Parvovirus B19 does not cause any of those but it leads to miscarriage, stillbirth and non-immune hydrops. Maternal
rubella exposes the baby to a high risk for ete, skeletal and heart defects, along with growth restriction, microcephaly, and
mental retardation. Congenital rubella syndrome may be associated in later life with diabetes mellitus, thyroid dysfunction and
even psychosis. Pre-pregnancy screening and widespread neonatal vaccination have greatly reduced neonatal morbidity in
developed nations. Congenital CMV is manifested as deafness, mental retardation, and jaundice. First infection in the mother
is associated with a 30% risk of congenital disease; recurrent CMV presents substantially lower risk to the fetus. Up to 90% of
the population has been exposed to the herpes simplex virus (HSV) , which can be transmitted through the placenta
leading to congenital herpes (skin vesicles, eye dagame, seizures and neurologic damage), and during delivery resulting in
neonatal herpes, which occurs as frequently as 1 in 3000 births and has devastating effects. 25% of babies can have
disseminated disease (of which 30% die); 30% have disorders in the central nervous system; and 45% have disease limited
to the eyes, skin or mouth.
Maternal syphilis is disastrous for the fetus since the organism crosses the placenta easily, and can affect any organ system,
most commonly the bone, brain, liver, lungs and heart. The risk is highest if the mother gets the infection during her
pregnancy or within four years before the pregnancy.
Toxoplasmosis is caused by the parasitic protozoa Toxoplasma gondii, and is most dangerous when the mother is infected
close to term. One-third of women who get a primary infection during pregnancy will have a baby with toxoplasmosis,
manifested by chorio-retinitis, hydrocephaly and intracranial calcifications.
Malaria is also caused by a parasite and is one of the most prevalent infectious agents causing pregnancy-related and
neonatal morbidity. In Africa, where it is endemic, 1 in 4 women at delivery have malarial infection. Its major effect appears
to be smaller babies because malaria-infected blood cells and inflammatory products can clog the interface between the
placenta and the fetus, decreasing its sustenance. Treatment in pregnancy improves fetal growth.
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