Complex sentence: On 3 December 2012, St James'Palace announced that the Duchess is pregnant with her first child and had been admitted to the private King Edward VII's Hospital Sister Agnes in London, where she remained for three days, suffering from hyperemesis gravidarum.
Split into simpler sentences: On 3 December 2012, St James's Palace announced that the Duchess was pregnant with her first child. She had been admited to the private King Edward VII's Hospital Sister Agnes in London, where she remained for three days, suffering from hyperemesis gravidarum.