It's a girl: Ryan Phillippe by ex girlfriend's side as she gives birth

Ryan Phillippe's ex girlfriend has given birth to a girl. 

Aspiring actress Alexis Knapp, 26, welcomed a 8lb baby named Kai on July 1, America's In Touch magazine reports. 

The Cruel Intentions star, 36, is said to have been by her side in the delivery room at Cedars-Sinai Medical Centre, despite questions surrounding the paternity of the child.

Baby news: Ryan Phillippe's ex girlfriend Alexis Knapp has given birth to a girl 

'It was a smooth delivery,' an insider tells the publication.  

The actor, who has two children Ava, 11, and Deacon, 7, with his ex wife Reese Witherspoon, has been involved in the pregnancy. 

Brief romance: Ryan with Alexis Knapp last year

'Ryan took Alexis to her last doctor's appointments and was there in the hospital when she gave birth,' the source added.

'He's waiting for the DNA test to see of he's the father, but he's acting like he is.'

Knapp dated Phillippe last summer, before splitting in October.

That same month he struck up a romance with Red Riding Hood star Amanda Seyfriend at a Halloween party hosted by Kate Hudson. 

Phillippe was in a relationship with Seyfriend when news of his ex girlfriend's pregnancy broke in March. The pair have since split.

The Lincoln Lawyer actor told a friends at the time that he wasn't sure that he is the father, but a source added: 'If it's his, he'll take responsibility.'

Not yet an established star, Knapp has only appeared in small roles in comedy movies Couple's Retreat and Percy Jackson & The Lightning Thief.

She is set to make an appearance in the upcoming Miley Cyrus film, So Undercover.

Phillippe divorced Witherspoon in 2006 amid reports alleging he had began an extramarital relationship with Abbie Cornish, who was his co-star in the war film Stop Loss.

Dad duty: Ryan with his son Deacon and daughter Ava