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Viral infections during pregnancy

23 December 2016, by MOTA F. & TORRES T.

1 - VARICELLA ZOSTER VIRUS (VZV)

1.1 - IN UTERO TRANSMISSION

During pregnancy, VZV can be transmitted through the placenta and be responsible for congenital varicella or neonatal varicella. A few pathological studies of infected placenta revealed granulomatous lesions associated with necrotic areas. The transmission rate was assessed in several studies: In a study of 14 fetus at risk of VZV infection between the 10th and 24th week of gestation, the research of viral DNA by PCR was performed on an association of chorionic villi samples, fetal blood and amniotic fluid. The infection rate was 20% in the first trimester and 100% in the second trimester. In a French study conducted from 1989 to 1994 on 107 women with varicella before 24 weeks of gestation, the rate of placental transfer (evaluated by cell culture, PCR on amniotic fluid and measurement of IgM in fetal blood) was 8.4% [1].

1.2 - PERINATAL TRANSMISSION

When delivery occurs during maternal incubation period, the child will not have varicella unless he/she is exposed to infection during the postnatal period. When maternal chickenpox occurs within the five days preceding the birth or two days after birth, the newborn develops a serious infection because maternal antibodies do not protect him/her. Children who are born more than five days after maternal varicella receive antibodies from their mother and therefore present with attenuated varicella.

1.3 - CLINICAL MANIFESTATIONS IN PREGNANT WOMEN

Varicella is responsible for mortality and significant morbidity in pregnant women [2]. Varicella pneumonia is the most common and serious complication, being responsible for cases of maternal death. Glomerulonephritis and myocarditis may occur, although they are very rare.

1.4 - CLINICAL MANIFESTATIONSIN THE FETUS AND IN THE NEW-BORN

• The rate of spontaneous abortion and preterm birth is 14.3% versus 5.6% during normal pregnancy.

Congenital varicella is associated with skin abnormalities (scars, anetoderma, skin atrophy, pigmentation disorders), ocular anomalies (chorioretinitis, anisocoria, microphthalmia, cataracts, optic atrophy), musculoskeletal anomalies (hypoplasia, agenesis, muscle atrophy) and neurologic abnormalities (microcephaly, encephalitis, hypotonia, mental retardation, cortical atrophy). It can cause fetal growth retardation or neonatal death. There is a risk of 2% of fetal malformation when seroconversion occurs early in the 2nd trimester (13-20 weeks). The risk is low and comparable to that observed in the general population, which supports the argument of not doing invasive procedures in case of VZV seroconversion during pregnancy, and to follow these pregnancies by periodic ultrasound [3].

• The mortality of neonatal varicella is 25% and the severity is far greater than the maternal rash that occurs in the five days before and two days after childbirth (given the delay in antibodies transmission).

Postnatal varicella begins between the 10th and 28th day of life. Transmitted maternal antibodies probably lessen the severity of the disease.

1.5 - DIAGNOSIS AND MANAGEMENT

• Exposure of pregnant women to VZV in the first two trimesters: if the exposure is recent, immediately determine the immune status of the mother by serologic testing. If it is positive, there is no risk of fetal infection. If it is negative, the risk is variable depending on the term (see above). Unfortunately, because of the transfusion risk, specific g -globulins no longer exist and the polyvalent Igs are weak. It may, however, be discussed whether to use immunoglobulins available at hospitals’ pharmacies in the event of negative serology and exposure in the last 72 hours.

Some authors advocate the definitive diagnosis by PCR of the amniotic fluid and eventually anti-VZV IgM measurement from the cord [1]. There are three problems with this attitude:

— the positivity of samples does not preview the severity of fetal damage and, in practice, the attitude to adopt towards the parents becomes very difficult in case of positivity if they want a therapeutic abortion;

— both techniques are dangerous with a risk of miscarriage on healthy child;

— there is no effective treatment.

Also we advocate ultrasound monitoring by a reference sonographer.

Exposure of pregnant women to VZV in the third trimester: when maternal varicella occurs five days before delivery, the serological diagnosis by measurement of serum antibodies must be repeated to determine the date to which delivery should be delayed, in order to allow the mother time to produce and transmit the child neutralizing antibodies, to mitigate the consequences of neonatal varicella.

In case of clinical signs suggesting the possibility of severe varicella in pregnant women (high fever, profuse and/or necrotic rash, cough, dyspnea), due to the risk of varicella pneumonia, which is often severe and sometimes fatal, it is necessary to consider hospitalization for initiation of treatment with IV acyclovir.

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