An unusual pregnancy

A 17-YEAR-OLD girl presents with her mother. She is 26 weeks pregnant with her first child and has just moved to the city. She has a “slow pulse”, for which she has been seeing a paediatric cardiologist annually since birth. She has no symptoms, does not exercise, takes no medication except iron/folate tablets, and has no other past medical history. She is a non-smoker and does not consume alcohol or recreational drugs. Her mother has a history of SLE with a photosensitive rash requiring Plaquenil therapy. Her father and two brothers are fit and well.

Examination reveals a