Varicella infection in preg women -Foetal harms

Ms H Begum, aged 29 yrs , primigravida , carrying 15 weeks of gestation  with normal NT scan and Double  marker reports  had an attack of a Varicella zoster on 01-07-20  is worried about foetal abnormalities  . Her husband has since gone to another country on contractual basis and can’t come home in next seven  yrs. She is worried about teratogenecity and reluctant to simply go ahead with MTP based on theoretical or should I say presumptive possibility of cong abnormalities. My Q to members can we offer any diag tests to confirm that fetus in question is really affected? If so what are those tests that I shall advise  her enabling her and myself that  there is almost certainly foetal affection?? After how many weeks of acute varicella such targeted scan can be imaged?? Additionally should we enquire about varicella  vaccine routinely to all women planning for pregancy or insist on  some Lab tests to confirm presence of antibodies in case she don’t remember details of  childhood vaccination??

When to do USG to pick up varicella induced changes??  Timing of USG?? Ans: A time lag of at least 5 weeks after the primary infection is advised because ultrasound performed at 4 weeks has failed to detect the deformities. Associated sonographic features of polyhydramnios fetal hydrops may add to specific findings in aiding diagnosis.

What about foetal MRI??   Fetal  magnetic resonance imaging can be useful to look for morphological abnormalities . Yet , ultrasound remains the best diagnostic modality to follow serially fetuses suspected or known to have varicella infection.

What to look for??  There is no definitive method but targeted ultrasound for 1)  limb deformity 2)  microcephaly  3 ) hydrocephalus  4)  gastrointestinal and 5)  genitourinary abnormalities ,6)  cortical atrophy 7)  soft tissue  calcification and 8)   intrauterine growth restriction  may be a method to assess the severity of infection.

Long term ill health: - This syndrome is manifest by : Dermatomal scarring , Limb hypoplasia, ocular abnormalities , Low birth weight , cortical atrophy and mental retardation , early infant death .

What is role of  amniocentesis  in this case ? Ans: VZV DNA can be detected by polymerase chain or culture in amniotic fluid.   VZV DNA has a high sensitivity but a low specificity for the development of CVS(cong varicella syndrome)

Why don’t usually don’t embark on amniocentesis so liberally? Ans: Stratification of risk in this case is very relevant.  Amniocentesis is not routinely advised because the risk of CVS(cong varicella syndrome)  is low even in the presence of positive VZV DNA in the amniotic fluid. If amniotic fluid is PCR positive for VZV and the ultrasound is normal at 17-21 weeks the risk of CVS is low. Serial follow up ultrasound are therefore advised and if repeat ultrasound is normal at 23-24 weeks the risk of CVS is remote. The risk of CVS(cong varicella syndrome)  is very high if the ultrasound shows features compatible with CVS and the amniotic fluid is positive. A negative result in amniotic fluid and a normal ultrasound from 23 weeks onwards suggest a low risk of intrauterine infection.

What about Cordocentesis in this case ??  Fetal bold sampling for varicella specific IgM antibody is not useful. While total IgM concentration may be elevated in setting of acute viral infection the detection of antibody  in the fetal compartment does not indicate the severity of fetal infection.

Prevalence of foetal infection: - The incidence of CVS has been previously reported to be as high as 2% when maternal infection occurs between 13 and 20 weeks gestation. A more recent pooled estimate from cohort studies suggests a rate of 1.4% in the second trimester and 0.55% in the first trimester . Virtually all cases occur in the first 20 weeks of gestation with the overall rate in this period being 0.91% .