AFTER a romantic birthday trip to Italy, head-over-heels-in-love KIM KARDASHIAN is determined to marry rapper KANYE WEST ASAP – and give birth to twins!

The reality TV star has ditched plans to have a baby by a surrogate mom, sources say, and she’ll spend the $200,000 she’d budgeted for that on cutting-edge fertility treatments.

“Kim originally planned to use a surrogate to preserve what she calls her ‘money-maker,’ that being her curvaceous shape,” a source close to her told The ENQUIRER. “But after their trip to Italy, she said, ‘All I want now is to be Kanye’s wife and the mother of his babies. I don’t care WHAT it does to my figure!’”

The “Keeping Up with the Kar­dashians” beauty is already said to be researching high-tech fertility treatments.

“Kim wants to make sure her first delivery will be twins,” con­fided the source. “But before that happens, Kim and Kanye plan to tie the knot in a lavish $20 million wedding as soon as her divorce from Kris Humphries is final.”

The couple has been dating for more than six months, and during their Italian getaway, 35-year-old Kanye treated his sweetheart to gour­met meals at the finest restaurants and swanky suites at the ritziest hotels.

Kim, who just turned 32, tweeted from Rome: “Italy is so beautiful! Best birthday ever!”

In a stunningly romantic gesture, Kanye presented Kim with a red rose when she donned a white lace wed­ding gown-inspired dress.

“Kanye has want­ed to marry Kim for years, and that pretty much sealed the deal,” continued the source.

But before their vacation, in­siders say Kim had been unsure of her commitment to Kanye.

“Kim and Kanye were having problems,” divulged the source. “He was resisting pressure from Kim’s mom Kris to play a bigger role in the family’s reality TV show, and they’d been fighting.

“But seeing pictures of a voluptuous-looking Kim on the beach in Miami had Kanye salivating. Some people may think she looks heavy in the front and rear, but Kanye loves her that way. Kim has always been his perfect woman. And while they were in Italy, Kanye showed Kim that he’s everything she’s ever dreamed of in a man.”

While Kanye told friends that he planned to pop the question during the lovebirds’ getaway in Rome, “they decided to wait,” another source told The ENQUIRER.

“They’re afraid that an engagement wouldn’t look good with Kim’s divorce from Kris still un­settled. But Kim is telling friends there’s nothing she wants more than to marry Kanye and have his children.

“Still, Kim’s a Kardashian at heart, and that means when she does marry Kanye, it will be one of the biggest, most extravagant weddings Hol­lywood has ever seen!”