**Core Concept**
The question is testing the association between congenital heart disease in newborns and various maternal conditions. Maternal infections, autoimmune diseases, and certain metabolic conditions during pregnancy can increase the risk of congenital heart defects in the fetus.

**Why the Correct Answer is Right**
Rheumatoid arthritis is an autoimmune disease, but it is not directly linked to an increased risk of congenital heart disease in the fetus. In contrast, systemic lupus erythematosus (SLE), diabetes in pregnancy, and congenital heart disease of the mother are all known to increase the risk of congenital heart defects. SLE can cause a hypercoagulable state and vasculitis, which may affect fetal development. Diabetes in pregnancy is associated with an increased risk of congenital heart defects, particularly hypoplastic left heart syndrome. Maternal congenital heart disease can also increase the risk of congenital heart defects in the fetus due to shared genetic and environmental factors.

**Why Each Wrong Option is Incorrect**
**Option A:** Systemic lupus erythematosus is associated with an increased risk of congenital heart defects, so it is not the correct answer.
**Option C:** Diabetes in pregnancy is also associated with an increased risk of congenital heart defects, so it is not the correct answer.
**Option D:** Congenital heart disease of the mother is a known risk factor for congenital heart defects in the fetus, so it is not the correct answer.

**Clinical Pearl / High-Yield Fact**
It is essential to identify and manage maternal conditions that increase the risk of congenital heart defects, such as SLE and diabetes in pregnancy. Regular prenatal care, including fetal echocardiography, can help detect congenital heart defects early in pregnancy.

**✓ Correct Answer: B. Rheumatoid arthritis**