As during her first pregnancy, Catherine
continues to suffer from hyperemesis gravidarum, the palace said. The condition
involves nausea and vomiting more severe than the typical morning sickness many
women suffer during early pregnancy.
Catherine's condition meant she was forced
to cancel some public engagements and led to the couple announcing her
pregnancy September 8 before the usual 12-week milestone. The palace said
Monday that her condition had improved.
William and Catherine's first child, Prince George,
was born in July 2013.
The second child will become fourth in line
to the British throne, regardless of gender.