Two weeks early... but that’s not unusual

As an older mother, Samantha Cameron is not unusual in giving birth early.

The risks do increase with women over the age of 35 but improvements in medical care mean any long-term impacts for the baby are minimal.

Triggers for women giving birth early include medical conditions such as high blood pressure, a lack of space in the womb and premature births running in the family. By this time in the pregnancy, the baby is usually about 19 inches long, and weighs about six pounds.

The baby is becoming chubby as fat layers build, has a fully developed pair of kidneys, its liver has begun processing some waste products and the only organs still to mature are the lungs.

The baby can also recognise its mother's voice and is able to react to any loud noises.