Royal baby: The three-month secrecy rule
Pregnancy - especially the uncertain, early months - is a very private time for most women, writes psychologist Donna Dawson. This is not an option for the Duchess of Cambridge.
Before the 12-week mark, a woman's body is getting used to the dramatic change in hormones and the accompanying changes in body shape, mood, energy and overall physical well-being. There's not much to see, and sometimes not even much to feel, and there is always uncertainty about how the pregnancy will develop.
Deciding just when to tell the world about the impending birth is very much the pregnant woman's prerogative.
Most people would like to keep their pregnancy quiet until 12 weeks. That simply wasn't an option for me.
I couldn't work, I was housebound. I am normally a very active, social person - suddenly I vanished from sight. With my second and third pregnancies, we needed the support of family and friends.
That also then meant that I had a public miscarriage, which isn't much fun for anyone - but what could I do?
I would so love to have enjoyed pregnancy - I was so excited when we started trying to start a family - and it was the worst time of my life.
Post-traumatic stress disorder is very common with this condition. You are throwing up constantly for months - that's like a torture they could use on people.
The countdown to the birth for me was excitement about not being sick any more.
For me the births were the easy bit - I would rather give birth naturally without any medication once a month, for nine months, than have hyperemesis gravidarum.
And after the baby arrives - the sleep deprivation, the intensity of it - is just not a problem. I am on cloud nine, I feel so well. Everything afterwards is easy compared with being pregnant.
The three-month secrecy rule is usually abided by, however, so that if anything goes wrong in the early stages, the expectant mother doesn't have to face taking back what she's already announced.
And baby gifts are normally not accepted until after the baby is born, as if to do so is to tempt fate.
To watch people's faces, hear their reactions and receive their congratulations as you give them your very special news is one of the exclusive perks of falling pregnant. When that moment is snatched away, as has just happened to the Duchess of Cambridge, it can feel very much like an anti-climax.
It is a reminder that in pregnancy, very little is under a woman's conscious control.
For most women, losing control of the timing of such a big announcement is very disappointing. For the duchess, it must feel like a double blow - not only will she be feeling sad that the announcement did not come initially from her and Prince William, but she will be feeling more stressed as the full glare of the media spotlight and public attention turn on her at a time when she is feeling at her weakest and most vulnerable.
It is embarrassing enough to talk about being sick - pregnant or not - but how much more so when the whole world is in on your secret?
It must feel like people are hovering over the sick bowl with you, as if you are living in a glass house where every mishap is on display. And in the future, it may feel as if she is giving birth in a goldfish bowl.
Embarrassed, vulnerable and invaded are all feelings the royal couple may be experiencing at the moment.
Pregnancy sickness symptoms are a very positive sign for the pregnancy, a sign that the pregnancy is working well.
Moderate symptoms are more of a nuisance, while women who have no pregnancy sickness symptoms actually find it more difficult to accept that they are pregnant.
But if you are getting pregnancy sickness symptoms at the very severe end, such that a hospital admission is required, it can be utterly overwhelming. You are not thinking of anything else - plans about telling people and celebrating pale into complete insignificance because the woman feels so, so appalling.
Women are only thinking about getting through the next 24 hours without vomiting their hearts up. Dads can feel very helpless, seeing their wives or partners feeling so awful with so little that they can do.
The condition used to be potentially fatal, before we had intravenous fluid therapy. The last recorded death was in the 1930s in the UK.
But it can still be fatal to developing foetuses in very rare circumstances. We do have women contacting the charity who say they had such severe symptoms, they had to terminate the pregnancy.
This can be an appalling condition.
What would not be ideal is if the duchess felt more stressed because the news of her pregnancy and illness are out.
Negative stress is not a good thing at the best of times, but particularly so in pregnancy. And when a pregnancy begins on a traumatic note, stress could cause a woman to stay in a negative frame of mind for longer, making her feel harassed, irritable and moody and putting extra strain on her pregnancy.
What would be helpful for the royal couple - now that the stable door is open and the horse has bolted - is to try to view any perceived negative as a hidden positive.
With the news out, it may help the duchess to think about and identify with the upside of such public interest. Everyone, especially women will be sympathising and rooting for her - even if she has to endure more well-meaning, homely suggestions such as "eat more ginger".
More attention will be given to extreme sickness in early pregnancy, and women with this condition will be taken more seriously - which can only be a good thing.
The nation will become more touchy-feely and baby-minded with the news of an impending heir. Magazines and newspapers will be full of articles on all aspects of pregnancy, and there will be an upsurge in young women attempting to become pregnant.
The people closest to the duchess will be able to show extra kindness and consideration.
However, she must brace herself for a deluge of home-made romper suits and gifts in the future, and the sharper scrutiny of an interested public. If she and her husband can go with this flow, it will put them both back in control of what is still, first and foremost, their pregnancy. And we, the public, will be waiting with bated breath for every announcement to come.