Celebrity News:

Cate Blanchett is pregnant. Normally this would be no one's business but hers, and possibly that of the man who got her that way, but this case is different. For Blanchett is a movie star, and the wombs of movie stars are important to us.

Celebrity pregnancies provide a fleshy tableau upon which we can heap an even greater level of body scrutiny than is usually the case with female stars. They provide sport for millions of body-watching women worldwide and, if the pregnancy weight goes to all the wrong places, they feed us dark pleasure in the form of Schadenfreude.

Blanchett is simply the latest in a merry conga-line of knocked-up celebrities. Perhaps it is all the soy milk they drink in Hollywood. Although childbirth is nothing new (by definition, it pretty much dates back to the dawn of mankind), every celebrity birth is treated by gossip mags and blogs with avid, Mrs Mangel-esque interest.

It begins with the "baby bump watch" - a sort of biddy-ish pastime whereby celebrities sporting a slight bloat, or wearing an empire-line frock, are branded pregnancy suspects.

The line between a bad photo angle and the existence of an embryo being a fine one, the only way to establish the facts is surveillance. So we are treated to a variety of possible pregnancy shots - double chins, swelling breasts and thickening ankles are all called into question, and supposedly pudgy celebrity abdomens are circled.

In some cases it turns out that the supposedly knocked-up celebrity is not nurturing the next Suri Cruise/Shiloh Jolie-Pitt/Lourdes Ciccone, but has just ingested some form of nutrition in the past 24 hours. The cause of their affliction is eating as opposed to shagging.

Nicole Kidman, who has had the audacity to reach 40 without bearing children (she has adopted two) is a constant subject of such speculation. In interviews she is consistently badgered about her childlessness, her journalistic interrogators like matronly aunts at a family barbecue, meaningfully tapping on their watches.

But Kidman is lucky, for the scrutiny only gets worse once the fact of pregnancy is established and the woman begins to show. A canny celebrity will learn how to "rock" her pregnancy - examples include the actress Halle Berry and the the pop singers Christina Aguilera and Gwen Stefani.

These stars are widely praised for their ability to appear both fecund and attractive (albeit aided by their superior genes and the pregnancy wardrobes that their fashion designer mates have customised to fit both them and their nascent celebrity spawn).