Who is the last first lady to give birth in 10 Downing Street?

The last first lady to give birth in 10 Downing Street was Mary Elizabeth Wilson, popularly known as "Bessie" Wilson. She gave birth to her daughter, Sarah, in 1939 while her husband, Harold Wilson, served as Prime Minister of the United Kingdom. This event marked the last time a baby was born at the official residence of the British Prime Minister.