Elsevier

The Lancet

Volume 353, Issue 9167, 29 May 1999, Pages 1829-1833
The Lancet

Articles
Mother-to-child transmission of toxoplasmosis: risk estimates for clinical counselling

https://doi.org/10.1016/S0140-6736(98)08220-8Get rights and content

Summary

Background

Women who acquire toxoplasmosis infection during pregnancy (in most cases detected through serological screening) require counselling about the risk of congenital infection and its clinical sequelae. Reliable estimates of risk are not currently available. We undertook an analysis of data from women referred to the toxoplasmosis reference laboratory, Lyon, France, between 1987 and 1995.

Methods

Information was collected from clinical notes kept at the laboratory and, where necessary, from the relevant obstetrician or paediatrician via telephone. Methods were developed to derive estimates of the risk of congenital toxoplasmosis by exact duration of gestation at maternal seroconversion.

Findings

We analysed obstetric and paediatric data on 603 confirmed maternal toxoplasmosis infections. At least 564 women received antiparasitic drugs according to a standard protocol. Congenital infection status was ascertained in 554 cases, and infected children were followed-up for a median of 54 months. The overall maternal-fetal transmission rate was 29% (95% CI 25–33), which masked a sharp increase in risk with duration of gestation from 6% at 13 weeks to 72% at 36 weeks. However, fetuses infected in early pregnancy were much more likely to show clinical signs of infection. These effects counterbalance, and women who seroconverted at 24–30 weeks of gestation carried the highest risk (10%) of having a congenitally infected child with early clinical signs who was thus at risk of long-term complications.

Interpretation

This information will assist the clinical counselling of pregnant women diagnosed with acute toxoplasmosis and may guide individual decisions on investigative and therapeutic options. Further studies are required to determine the long-term risks of clinical symptoms and disability due to congenital toxoplasmosis.

Section snippets

Inroduction

Toxoplasma gondii infection acquired during pregnancy can cross the placenta and cause congenital toxoplasmosis.1 Prenatal serological screening to detect maternal infection is used in many European countries,2 although the benefits and costs have not been adequately assessed.3 After detection of maternal infection, patients are faced with decisions about invasive investigations for fetal diagnosis and drug regimens with potential adverse side-effects, and the possibility of a therapeutic

Patients

We collected data on women referred to the laboratory between August, 1987, and October, 1995, during which time standard protocols were used. The analysis is limited to women in whom infection occuring during pregnancy was confirmed. In an attempt to eliminate major sources of bias we excluded women if there was any doubt that the referral had been prompted by suspicion of infection in the fetus or infant (eg, positive amniocentesis or clinical symptoms); excluded women if specific IgG

Results

The analysis is based on 603 confirmed maternal infections. Three women gave birth to twins, all born with concordant infection status. Data are reported on the first-born twin only. No woman was known to be HIV infected or to have any other disorder that might compromise her immune response. Clinical symptoms associated with maternal infection were reported by only 36 (5%) women. The mean age at referral was 24 years (range 16–44).

Antiparasitic treatment was prescribed for 564 women (at least

Discussion

Our study provides important information about the risks of congenital toxoplasmosis and the clinical sequelae for infants of women who seroconvert during pregnancy. Further studies are needed to quantify the risks to the fetus in women who are found to be IgM seropositive at the first test in pregnancy, although these will be substantially smaller. Previous estimates were based mainly on referrals for prenatal diagnosis of infection, which do not cover late maternal infections since

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