How do dogs know when you're pregnant? And what are the other behavioural signs?

A dog's senses of hearing and smell are much more powerful than those of a human. These would have been extremely important in the wild as they would have helped it to sense predators. It is because of these heightened senses that people "employ" guard dogs to protect their property, sniffer dogs to detect drugs and explosives, guide dogs for the blind, hearing dogs for the deaf, and why dogs are also ideally equipped to take part in search and rescue missions.

This increased sensitivity somehow also enables them to sense natural disasters before they happen. There are many accounts of how animals (including dogs) acted strangely before the recent tsunami in Southern Asia, as if they knew that it was about to happen.

National Geographic says the following:

"The belief that wild and domestic animals possess a sixth sense - and know in advance when the earth is going to shake - has been around for centuries.

Wildlife experts believe animals' more acute hearing and other senses might enable them to hear or feel the earth's vibration, tipping them off to approaching disaster long before humans realize what's going on."

It has also been reported that dogs are able to detect the subtle changes that occur in the body when cancer is present.

Knowing all of these things, it's hardly surprising that dogs can also detect when women are pregnant. There's no scientific evidence to explain how they know this, but there are a couple of theories about it. Firstly, it's possible that with their heightened senses, dogs can smell the changes in hormones and pheromones that occur in a woman's body during pregnancy. They may also be able to detect the emotional and behavioural changes that pregnant women go through.

And when a dog detects your pregnancy, it might start acting very differently towards you. Some dogs become much more protective of the woman, and of her bump; as if they know that there's another little person inside that they need to look after! While others may become jealous of this new rival for your affections!

Here are some very pertinent real-life examples of these amazing doggy super-senses.

Sometimes other (perceptive) humans may be able to detect that you're pregnant; - not from sniffing hormones and pheromones (unless they're unusually talented in this area!), but because of the way that you may behave when you're pregnant.

During those early weeks before the first scan most people want to keep their pregnancy a secret, but even if you're not showing during that time, you may unconsciously be giving off signals.

With the massive hormonal changes that are taking place inside your body, it's not surprising that your behaviour and your emotions might alter. Apart from perhaps turning a bit green and having to throw up a lot, you may experience some of the following behavioural changes:

• An increased sense of wellbeing and happiness (from the hormonal changes, and probably also from the excitement of being pregnant). This can change your entire personality; a normally serious and fretful person might become light-hearted and optimistic.

I know about this first change from personal experience, as my newly sunny disposition alerted my (rather observant) boss to my being pregnant!

• Hormonal changes can also cause you to become more emotional; more sensitive to sad or happy things. They can also make you feel more stressed, and cause you to become irritable in situations when you normally would not.

• From very early on in your pregnancy, you may feel much more tired than normal.

• Hormonal changes when you become pregnant can cause frequent urination, and then your uterus begins to press on your bladder from as early as 6 to 8 weeks of pregnancy.  So it's possible that you might have to pop to the toilet quite a lot!

• You might start to get incredibly hungry as if you're eating for two right from the start; - even though your baby's still the size of an apple pip!

• Cravings can also start quite early on, and some women crave some very strange things!

• Your sense of smell may become a lot more heightened, so you might react unfavourably to certain smells that you come across. (I couldn't stand the smell of coffee or garlic; previously two of my favourite smells).

• Some women suffer from headaches in early pregnancy, which can make it difficult to concentrate.

• It's also quite common to become a bit forgetful.

Of course, not every pregnant woman will experience all (or indeed any) of these things, and sometimes these changes may be so subtle that nobody would notice them. But even if somebody did suspect that you were pregnant they would be unlikely to ask you anyway, as it's difficult to be 100% sure. And it would be embarrassing to be wrong! Only dogs (and other animals) can know for sure.