How long should you wait to tell others you’re expecting?

WATCH ABOVE: Prince William and the Duchess of Cambridge, Kate Middleton, are expecting their second child – but the Duchess has been suffering from severe morning sickness. Stuart Greer reports.

TORONTO – In her first pregnancy, Kate Middleton dealt with morning sickness so severe she was hospitalized. And the bouts of nausea are back – on Monday, Prince William and his wife, the Duchess of Cambridge, announced they’re expecting their second child.

This time around, Middleton is being treated at Kensington Palace. She’s suffering from hyperemesis gravidarum, which requires supplementary hydration and nutrients.

But royal watchers are speculating that Kate’s pregnancy hasn’t even passed the 12-week mark. Instead the couple was forced to announce the pregnancy to explain why Middleton was skipping out on a string of appearances.

Middleton is already missing a scheduled appearance with her husband in Oxford on Monday. It’s also unclear if she will be making her first solo trip overseas to Malta that was slated for later this month.

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READ MORE: Prince William and Kate expecting second child

But if Middleton is past the first trimester, she didn’t necessarily jump the gun in announcing the big news, Dr. Doug Hepburn says. Typically women are advised to wait until the three-month mark before telling extended relatives and colleagues that they’re expecting.

“If you tell everyone and then you miscarry, people you don’t know well will be bringing it up and you’ll have to explain it,” Hepburn said. He’s an obstetrician at Oshawa, Ont.’s Lakeridge Health, medical director of the Durham Fertility Centre and an associate professor at Queen’s University.

It’s important to wait because the first trimester can be a tumultuous time for expectant moms.  There’s a 15 to 20 per cent risk of miscarriage up to the first 12 weeks, he said.

But that doesn’t mean you shouldn’t tell others about your pregnancy: that good news should be shared with close family members and friends.

“If you don’t tell anyone and you miscarry, you have no support systems. You certainly want to tell your best friend and family,” he said.

Manavi Handa, a midwife at Toronto’s West End Midwives and Ryerson University professor, says that the three-month waiting period is the traditional route. She tells her patients that if they’re not okay with the possibility of sharing bad news, they should keep the pregnancy to themselves. But if they’re comfortable with potentially having to tell people they had a miscarriage, they can talk about expecting.

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That applies to family and friends, close or distant to you.

She told Global News that if you don’t want people to know you had a miscarriage, “don’t tell them you’re pregnant.”

In the vast majority of cases, miscarriages happen in these early stages because the pregnancy is abnormal right from the onset. It’s a matter of chromosomes dividing improperly, Hepburn explained. Initially, the cells around the egg are maintaining the pregnancy, but at the 10- to 12-week mark, the placenta takes over hormonal control of the pregnancy. That’s typically when the miscarriage will present itself, Handa said.

After the 12 weeks, though, you should be in the clear. The risk of a stillbirth is about three in 1,000.

Middleton is also coping with hyperemesis gravidarum, and Hepburn wants readers to know: it’s a severe condition and it shouldn’t be downplayed.

READ MORE: What is the severe morning sickness known as Hyperemesis Gravidarum?

It’s described as incessant vomiting and nausea – or as Hepburn describes, the expectant moms can’t keep food or water down. In turn, their potassium levels drop and doctors need to monitor hydration and electrolyte levels.

“It’s not a psychological problem. They will hear from people that it’s in their head, it’s not that bad and it’s normal,” he said.

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Only two per cent of women deal with symptoms so severe that they become dehydrated.