Neonatal lupus is a rare complication associated with the presence of certain autoantibodies in the mother: anti-SSA (also called anti-Ro) or SSB (or anti-La) that can affect the foetus or newborn. The mother sometimes has lupus or Sjögren syndrome.

These antibodies are able to cross the natural barrier of the placenta, between mother and foetus, and can interact with certain organs of the child. They then cause:

A rash in the newborn, which resembles cutaneous lupus (hence the name neonatal lupus)

A slowing of the electrical conduction of the foetal heart, called congenital heart block (CHB), occurring without a birth defect

More rarely, liver disease or neurological disorders

The neonatal rash regresses spontaneously, as the mother's anti-SSA antibodies are gradually eliminated.

On the other hand, the slowing of the electrical conduction of the heart persists most often and may justify fitting the child's heart with a pacemaker in the 1st week after delivery.

It is very important to specify that the risk of slowing down the electrical conduction of the heart is low: 1% of children of mothers carrying anti-SSA antibodies are at risk. This risk increases to 15-20% when the mother has already had a child with this dysfunction.

In a lupus patient, the presence of anti-SSA antibodies may justify monitoring the child's heart by ultrasound, especially in early and mid-pregnancy.

The development of neonatal lupus does not presuppose the development of lupus in childhood or adulthood.