It’s official: Kate Middleton is pregnant

After months of rumors, it's finally official: Kate Middleton is pregnant.

In a statement issued on Monday, St. James's Palace in London confirmed Middleton, the 30-year-old Duchess of Cambridge, is expecting her first child with Prince William. The palace declined to specify how far along Middleton is in her pregnancy, only that she is in her "very early stages."

The news comes 19 months after the two were married in an extravagant royal wedding at London's Westminster Abbey—a ceremony that was almost immediately followed by rumors of an impending royal heir. For months, tabloids, both in the U.S. and overseas, have been on watch for a royal baby bump, predicting for months that an announcement could come any day.

But William and Kate, who dated on and off for nearly nine years before marrying, were silent on the rumors, which had intensified in recent weeks. But it appears the couple couldn't keep their secret any longer, in part because of Kate's health.

According to a statement issued by the palace, the princess was admitted to King Edward VII Hospital in Central London on Monday suffering from hyperemesis gravidarum. That's the medical term for very acute morning sickness, which requires additional hydration and nutrients. William was at his wife's side, according to the palace, and Middleton is expected to be hospitalized for several days, followed by a period of bed rest.

Not surprisingly, the news of a coming royal heir immediately captivated a public that has obsessed over every detail of William and Kate's relationship—from their first meeting as students at the University of St Andrews in Scotland in 2001 to their 2011 wedding, which was viewed by an estimated 300 million people around the world.

On Twitter, the hashtags "royalbaby" and "Kate" were trending worldwide—with everyone from elected officials to random celebrities weighing in on the royal offspring.

"KATE MIDDLETON'S UNBORN CHILD SHALL SAVE US FROM THE FISCAL CLIFF!!!" Damon Lindelof, the creator of "Lost," joked in a message on Twitter.

British Prime Minister David Cameron was one of the first public officials to offer his well-wishes to the couple, writing in a Twitter message that he was "delighted" by the news of Middleton's pregnancy. "They will make wonderful parents," Cameron tweeted.

At the White House, President Barack Obama and first lady Michelle Obama offered their congratulations through press secretary Jay Carney. Asked if Obama had any advice for the soon-to-be new parents, Carney said he hadn't had that conversation with the president.

But Carney said the Obamas "feel that having a child is one of the most wonderful parts of their lives" and were sure William and Kate would feel the same way.

The public scrutiny over when William and Kate would become parents seemed reminiscent of William's own arrival into the world.

His mother, the late Princess Diana, became pregnant just four months after her 1981 wedding to Prince Charles. Like Kate, Diana also reportedly suffered severe morning sickness during her pregnancy, which forced her to cancel numerous public appearances.

Until Monday, Middleton had kept up a normal routine. Last week, she was photographed playing field hockey during a visit to her old prep school.

The disclosure of the royal pregnancy comes after a challenging year for William and Kate, who have weathered public scrutiny of their first year as man and wife. The couple navigated an embarrassing public scandal last summer over topless photos published of Kate that were taken by a paparazzo during the royal couple's vacation.

William and Kate's child is expected to be a leading member of the royal family—not least because William is second in line behind his father, Prince Charles, as heir to the British throne. The new baby will be third in line, edging out William's brother, Prince Harry.

And because of a recent change implemented by the monarchy, William and Kate's first-born child will be the first royal offspring to be in line for the throne regardless of gender.

During the couple's royal tour of the Far East in September, William revealed during a meet-and-greet with students in Singapore that he and his wife hoped to have two children. Some royal watchers speculated it was during that trip that Kate became pregnant—though the palace has not said exactly when the baby is due.

Rachel Rose Hartman contributed to this report.