Neonatal lupus (NL), a passively-acquired autoimmune disease associated with maternal anti-SSA antibody, presents both cardiac manifestations such as cardiac NL and non-cardiac manifestations including rashes, cytopenia, and hepatic abnormalities. Cardiac NL, occurring in 1-2% of anti-SS-A antibody-positive mothers, is a life-threatening complication with a mortality rate of 20% and a pacemaker implantation rate of 70%. In contrast, cutaneous NL, which is more common than cardiac NL, usually resolves in six months. Since half of NL cases occur in asymptomatic mothers, if an infant presents characteristic cutaneous or cardiac manifestations of NL, the mother should be tested for anti-SS-A antibody. In mothers positive for anti-SS-A antibody, the risk of having a child with cardiac NL increases ten-fold and five-fold for a previous child with cardiac NL and cutaneous NL, respectively. A joint American, British, and French retrospective study of NL registries showed that hydroxychloroquine (HCQ) reduced the cardiac NL risk in subsequent pregnancies in mothers who previously had a child with cardiac NL. A prospective open-label study to confirm this effect is being undertaken in the USA. A similar prospective multi-center study will be undertaken in Japan. Establishing a Japanese registry of children with NL and subsequent pregnancies of their mothers will help promote clinical research in NL in Japan.