IT’s baby-on-board time for ELLEN DeGENERES and PORTIA de ROSSI but WHO’s providing the swimmers?! 

After four years of marriage, Portia has persuaded talk-show host Ellen, 54, to start a family – and friends say they hope to have a bundle of joy at home within a year!

“Portia put the baby issue on the back burner for years knowing Ellen wasn’t altogeth­er receptive,” the friend says.

“I think Ellen has had mis­givings about chasing after a young one when she’ll be into her 60s. But Portia turns 40 in January, and in the end, Ellen loves Portia with all her heart. If a baby is that important to Portia, Ellen can’t say no to her.”

The couple considered in vitro fertilization, with “Arrested Development” star Portia carrying their child, but ultimately decided to go with a surrogate with Portia’s eggs being used, sources say.

“Now the biggest question is who the male donor will be,” said the friend. “But once they clear all the hurdles, next year is going to be the year for them.”

With Ellen juggling her talk show, her duties as a pitch­woman for JCPenney and COVERGIRL, plus running her own record label and pet food company, Portia will be a stay-at-home mom, sources say.

“Portia has assured Ellen she doesn’t need to slow down one bit,” the friend says. “Portia loves her acting career, but it’s a small part of her life. What she wants most is happiness with Ellen and sharing their love with a child.”