Ashlee Simpson and Pete Wentz are reportedly set to have a Halloween baby.

The couple – who are expecting their first child together later this year – were said to be thrilled when they found out they were expecting a daughter due on October 31.

A source told America’s Star magazine: “Ashlee and Pete are on cloud nine. The doctor told them they actually conceived the baby just before Valentine’s Day (02/14/08) while they were on vacation and has given them an initial due date of October 31.”

Fall Out Boy rocker Pete – who loves the spooky holiday - is reportedly especially pleased he will welcome his new baby into the world on the scary day.

The source added: “When Pete heard he might have his baby on Halloween, he went nuts. For a rocker type like Pete, that would be just too perfect!”

It was recently reported Ashlee, 23, has embarked on a strict exercise regime to avoid gaining too much weight during the pregnancy.

A source said: "She's still clinging to the hope that she can limit her total weight gain to no more than 30 to 35lbs. So she is doing low-impact exercises, such as riding the stationary bike and Pilates."