INFECTIONS IN PREGNANCY – CHICKEN POX

 DEFINITION:

Primary infection caused by the varicella zoster virus (VZV). VZV causes chickenpox, which is also called varicella, and shingles, which is also called herpes zoster.

ASSOCIATIONS/RISK FACTORS:

No prior immunity, immigrant population from tropical or subtropical areas (note: can be transmitted via patients with shingles).

EPIDEMIOLOGY:

Complicates 3 per 1000 pregnancies, about 90% of pregnant women do have immunity.

HISTORY:

Fever, malaise, pruritic rash (becomes vesicular then crusts over). The clusters of blisters typically appear one to five days after the rash develops. The affected area may feel itchy, numb, and very sensitive.

EXAMINATION:

Vesicular rash. Dewdrop on rose petal pattern of Vesicle.

PATHOLOGY/PATHOGENESIS:

Herpesviridae, Enveloped, Icosahedral DNA virus (herpes family), highly infectious. The virus itself remains dormant in the body. If the virus is reactivated, it can emerge as herpes zoster.

Spread: Aerosol route, direct contact with vesicular fluid, indirectly via fomites.

Incubation period: 1–3 weeks, infectious from 48 hours prior to the rash forming until                                                 vesicles crust over.

Dormant period: Following primary infection the virus lies dormant in sensory nerve root                                              ganglia and may reactivate as shingles.

INVESTIGATIONS

Bloods: Varicella zoster IgM (active infection) or IgG (immunity).

USS: Fetal anomaly scan (fetal varicella syndrome).

MANAGEMENT

Non-immune mother: Give VZIG.

Established chicken pox:  

    Aciclovir (800 mg PO q4hr while awake (5 times daily) for 7-10 days, works better if started within 24 h of onset of rash (with caution prior to 20 weeks). Dose adjustment to be made based on renal clearance, frequency to be reduced to q6hr or q8hr or q12hr.

LABOUR: Avoid elective delivery for 5–7 days after rash appears

(allows placental transfer of maternal antibodies).

Neonate: Requires VZIG if delivered within 7 days before or after onset of maternal rash.

BREASTFEEDING: With appropriate hepatitis B immunoprophylaxis, breast-feeding does not appear to  pose additional risk for transmission from infected hepatitis B virus carriers to their infants.

COMPLICATIONS

Maternal: Pneumonia (10%), Secondary infection, Septicaemia, hepatitis, encephalitis,             myocarditis, death (rare). Very rarely Thrombocytopenia and purpura.

Fetal: Fetal varicella syndrome (if maternal infection before 28/40): skin scarring, eye defects, limb deformities, neurological abnormalities.

Neonatal: Varicella infection of the newborn (if maternal infection 1–4 weeks prior to delivery to 1 week postpartum).

PROGNOSIS:

If exposed earlier, VZIG reduces risk of maternal infection to 50% in the non-immune. No increased risk of miscarriage.