Table 1 Toxoplasmosis, listeriosis and CMV infections

Toxoplasmosis

Toxoplasmosis is caused by the protozoa Toxoplasma gondii[11] which can be transmitted by the pregnant woman to the foetus. Infection can occur through ingestion of viable tissue cysts in undercooked meat or through contact with oöcysts excreted by cats in the environment [12]. The incidence rate of congenital toxoplasmosis in the Netherlands is two infected children per 1000 live births. This is ten times higher than in Denmark [13], for example, and twenty times higher than in Ireland [14]. Primary infection with Toxoplasma gondii in pregnancy can lead to severe illness in the foetus and infant, including chorioretinitis, deafness, microcephaly, developmental delay and even stillbirth [15, 16]. Transmission is rare in early pregnancy and increases with duration of pregnancy. Transmission frequency is approximately 15% in the first trimester, 30% in the second trimester and 60% in the third trimester of pregnancy [15]. Exposure to infection acquired in the first trimester causes more severe congenital illness and foetuses exposed in the third trimester are more likely to be asymptomatic at birth [15].

Listeriosis

Listeriosis, a food-borne infection caused by the bacteria Listeria monocytogenes is 17 times more likely to occur in pregnant women than in the general population [11, 17]. Outbreaks of listeriosis occur mainly by consuming unpasteurized dairy products, smoked fish and ready-to-eat foods [17]. In the Netherlands, the estimated incidence rate of pregnancy-related listeriosis is between 1.3 and 2.4 cases per 100,000 pregnancies over 24 weeks of gestation [18, 19]. Even though listeriosis is a rare disease, it can have serious consequences. Twenty percent of pregnancies complicated by listeriosis end in spontaneous abortion or stillbirth, and two-thirds of surviving infants develop clinical neonatal listeriosis. Moreover, listeriosis has a high case-fatality rate: 20–30 neonatal deaths per 100 cases of illness [11, 17].

Cytomegalovirus

A cytomegalovirus (CMV) infection is the most common viral infection during pregnancy and the most common cause of congenital defects in newborns [11], with an estimated worldwide prevalence of 6.4 cases per 1,000 births [20]. Transmission occurs through contact with infected body fluids [21]. The incidence rate of congenital CMV in pregnant women in the Netherlands is 5.4 cases per 1000 [22]. In 30 to 40% of the pregnant women with a primary infection and in less than one percent of recurrent infections the foetus will be infected [23]. Ten to 15 percents of the infected foetuses have symptoms of the disease at birth (e.g. hepatosplenomegaly, intracranial calcification, chorioretinitis). Another 15–20 percent of the infected foetuses will develop symptoms during their first years of life (e.g. physical and mental retardation or hearing loss) [23]. A common way to require a CMV infection is through close contact with young children, who can secrete the virus in their saliva and urine for many months after their first infection. Women who are working in a child day care setting and women who have young children run a higher risk of infection [3].