Why is there an unfinished area on the lap of Mrs. Andrews in Mr. and Mrs. Andrews?

The unfinished area on the lap of Mrs. Andrews in the oil painting Mr. and Mrs. Andrews by Thomas Gainsborough remains a subject of historical speculation.

While the exact reason for the blank space is not definitively known, a prominent theory suggests that the area was intentionally left unfinished to be filled in later with a portrait of a baby, perhaps to commemorate a future addition to the family.1

The painting, which depicts the couple on their private estate in Sudbury, is considered one of Gainsborough's early masterpieces. It is notable for blending his skills as both a portraitist and a landscape painter, a combination that defines much of his career.12