The star of US comedy New Girl and producer Jacob met on the set of film Rock The Kasbah last summer which Jacob had been producing.
They made their red carpet debut at the 2014 Emmy Awards, confirming speculation that the pair were dating just weeks after she split from screenwriter Jamie Linden. It was her first serious relationship following her 2011 divorce from Death Cab For Cutie frontman Ben Gibbons.
Speaking of their pregnancy, the pair admitted: "Jacob and I are over the moon. We are so excited to meet our little one."