Greta Gerwig and Noah Baumbach have welcomed their first child together.

Greta Gerwig

Greta Gerwig

The 35-year-old actress and her director boyfriend - who has a son Rohmer, nine, from his previous marriage to Jennifer Jason Leigh - have become parents, her rep has confirmed to PEOPLE magazine.

The happy news comes just days after they were spotted pushing a pram around Manhattan on Tuesday (19.03.19).

An eyewitness told E!: "Noah was pushing and Greta was right next to him. They were chatting and enjoying some fresh air.

"They were bundled up in the chilly weather and they had a grey and white striped blanket draped over the stroller.

"It seemed like the baby was sleeping because they were busy talking and didn't have to tend to the baby.

"They walked around their neighbourhood for several blocks before heading home."

The couple's news comes nine years after they first met when Noah cast Greta for his 2010 movie 'Greenberg', which also starred Ben Stiller.

The pair have since gone on to co-write movies 'Mistress America' and 'Frances Ha'.

Greta wrote and directed 2017 comedy-drama movie 'Lady Bird', for which she was nominated for Academy Awards for Best Director and Best Original Screenplay, and a Golden Globe for Best Screenplay.

While they have a mainly private relationship, Noah supported her at both ceremonies.

Greta worked alongside Saoirse Ronan in 'Lady Bird', in which the star portrayed the lead character Christine "Lady Bird" McPherson, and the 24-year-old actress admitted the filmmaker has been "very supportive" since she finished filming the motion picture.

She said: "I was a huge fan of Greta Gerwig before I worked with her on 'Lady Bird'.

"Meeting Greta and knowing that she knew who I was and wanted to talk to me about the script was so exciting. We Skyped before we met and we were so giggly, like two kids in high school. She's been very supportive since."