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Microbial Infections That Cause Stillbirths (Part I)

By Tayo Fasuan

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Stillbirth is defined as no sign of life in a neonate at delivery, and it is one of the most terrifying outcomes of any pregnancy. According to some researches carried out in 2006, the annual rate of stillbirths in the world is above 3.2 million, with 98% of this figure occurring in low-income and middle-income countries. Also, 50% of all stillbirths have been found out to be due to infections, which are bacterial, viral, fungal and protozoan in origin.

Most often, the reasons for infection-related stillbirths are not clear due to the fact that medical records during pregnancies usually do not contain histories of infections. Even when infections are discovered, there is usually still no evidence to link the infections directly to the death of the foetuses. However, it is known that infection can initiate a chain of events leading to stillbirth without being discovered.

According to a review done by Robert Goldenberg and his colleague in 2010, various mechanisms can be employed by infectious organisms in causing stillbirths. For instance, maternal infection might lead to systemic illness with the mother becoming severely ill and the foetus might die because of high maternal fever, respiratory distress, or other systemic reactions, without the organisms transmitted to the placenta or foetus.

Also, the placenta might be directly infected, resulting in reduced blood flow to the foetus, or the foetus might be directly infected with damage to a vital organ. An infection in the early stage of pregnancy might later result into the death of the foetus at a later date, while a maternal infection of the genital tract or elsewhere might precipitate preterm labour that the foetus is unable to tolerate.

About 40 organisms, including bacteria, fungi, viruses and parasites have been identified as causative agents of stillbirths in women with concrete evidences, with many of them being animal-borne (zoonoses) or vector-borne. Some of the most common and important ones present in Africa, especially Nigeria, being populated with low-income and middle-income individuals, are discussed here.

Bacteria

Over 130 different bacteria can cause intrauterine infections, and many of these have been associated with stillbirth. The percentage of pregnancies affected by bacterial infection is much higher in countries of low and middle income than in those of high income. Bacterial infections leading to stillbirth can be divided into those that reach the foetal compartment through the placenta, and those that ascend from the vagina through the cervix. While syphilis is the most prevalent cause, there are other microorganisms which can cause stillbirths too.

  • Syphilis:

Syphilis is the most prevalent cause of all infectious causes of stillbirths in the world. The disease stands out because the disease causes a large number of stillbirths though it is highly preventable. Syphilis is caused by Treponema pallidum, a microbe belonging to a group of bacteria called spirochaetes, with the ability to cross the placenta and infect the foetus. The risk of foetal infection related to the stage of maternal syphilis.

If the mother is infected but untreated, about 40% of foetuses will die in the uterus and another 30–40% will be born alive but will have congenital syphilis. The most common cause of foetal death has been suggested to be placental infection with decreasing blood flow to the foetus, although direct foetal infection has also been indicated. In some areas of sub-Saharan Africa, 25–50% of all stillbirths are associated with syphilis.

Despite this alarming rate, stillbirth due to syphilis is totally preventable. Within a functioning health system, screening of pregnant women for syphilis is feasible, and once disease is diagnosed, treatment is easy and inexpensive. The reasons for the present failure to eliminate congenital syphilis, especially in sub-Saharan Africa, include poor access to prenatal care or use of such services, and failure to provide appropriate treatment for syphilis because of lack of resources, poorly functioning supply systems, and other priorities such as HIV screening and treatment. Due to this, it has been suggested that point-of-care rapid testing and treatment could be the most cost-effective method to reduce adverse pregnancy outcomes associated with syphilis. Based on many reports and data about these preventable occurrences of stillbirths due to syphilis, WHO has launched a programme to eliminate congenital syphilis worldwide.

  • Other Bacterial Infections

A stillbirth-associated infection caused by another spirochaete is Lyme disease, caused by Borrelia burgdorferi. There have been reports of small series of stillbirths associated with maternal Lyme disease with most foetal deaths occurring in the mid-trimester. This spirochaete and others have been found in the liver, spleen, kidney, and brain of foetuses. However, few stillbirths are associated with Lyme disease except in highly endemic areas. Another spirochaetal disease associated with adverse pregnancy outcomes, mainly in sub-Saharan Africa, is tick-borne relapsing fever, caused by Borrelia duttonii, whose contribution to stillbirths is relatively unknown. Other non-spirochaete causative organisms include Listeria monocytogenes, which is acquired when pregnant mothers eat contaminated food such as unpasteurised soft cheese or undercooked meat. If and when the organism is disseminated into the blood (bacteremia), the organisms are transmitted to the placenta and can cause necrosis and microabscesses. The organisms can be transmitted to the foetus, and occurrence of stillbirth is attributed to both placental dysfunction and foetal infection. Other infections and microbes capable of causing transplancetal infections include maternal tularaemia, clostridia, anthrax, typhoid fever, brucellosis, Haemophilus influenzae, Pseudomonas pyocyanea, the plant bacterium Agrobacterium radiobacter, and Mycobacterium tuberculosis.

To be continued…

Updated: July 27, 2014 — 3:07 pm

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