How and why the maternal body makes adaptations and allowances for another 'foreign body' to thrive and survive inside it is not fully understood. If any other tissue had to grow at the rate a foetus does, it would be attacked and destroyed immediately. It is truly a wonder of nature. Think about what is going on under your very nose, and thank your body for the miracle it is performing. Not only does it provide shelter for this little being, but food and warmth as well.

Oxygen is actually food that filters through to the baby. With every breath inhaled, you are nourishing your own body as well as that of your baby. But as the uterus grows, it places pressure on the diaphragm (the muscle above the abdomen). This changes the way the lungs function so that when you breathe in, the diaphragm cannot be drawn down as far. This is why many women feel as though they cannot inhale deeply enough.

But your body compensates for this crowding by allowing the rib cage to flare out and supply adequate room for the lungs. As a result, 30 to 40% more air can be inhaled in a single breath and, between weeks 16 and 40, oxygen onsumption increases by another 15 to 20%.

When performing vigorous activities, however, a pregnant woman has a smaller oxygen reserve and will become breathless more quickly. But this is only temporary. When you relax again, your body will fight to repay the oxygen debt. For 20 minutes the foetal heart rate is faster as it catches up.

During pregnancy, blood flow increases to keep pace with the extra workload on your internal organs and to satisfy your baby's demand for oxygen and nutrients. In fact, your blood volume almost doubles.

Normally this would cause soaring blood pressure, but the body makes remarkable adjustments. A miracle hormone called progesterone is produced. It softens all the muscles of the body during pregnancy, allowing the veins and arteries to stretch and accommodate the increased blood volume. The heart increases in size and its walls thicken as it works harder to handle the increased blood volume. The blood also becomes thinner.

High blood pressure during pregnancy has to be avoided as it can impair circulation to the foetus through the placenta. Oxygen and nutrients are passed through to the baby via the placenta and the umbilical cord, but at no time do the mother's and baby's blood mix.

Eating for two is unnecessary. Digestion slows down dramatically during pregnancy and food sits in the intestine for longer. There is a very good reason for this. It allows the placenta more time to 'milk' the nutrients from the consumed food.

Again, this is made possible by progesterone. All the smooth muscle tissues in the body soften, including the stomach and intestines. Unfortunately, this also explains those all too familiar niggles ? heartburn, constipation and nausea.

The kidneys now have to get rid of waste for two. They work much harder to filter the blood and maintain a balance of water, salt and other elements. To cope with this additional workload, the kidneys increase slightly in size and more urine is produced. But this is no excuse to drink less water, as dehydration brings problems of its own.

The bladder is also affected by progesterone and bladder infections are more common during pregnancy.

The metabolic activity of the cells of the body increases during pregnancy, causing more heat to be produced. This is why any pregnant woman will tell you she's always hot, even when it's cool. The body compensates for the increased temperature by stepping up perspiration. So don't be alarmed if you perspire profusely during pregnancy. It's the body's way of cooling down.

But research suggests that overheating can be fatal to the woman and the foetus. Exposure of the foetus to high temperatures, because of an infection in the mother, may be responsible for neural tube defects. This would affect the development of the central nervous system, especially during the first trimester when the neural tube is being formed.

So it is advisable not to take very hot baths, steam baths or saunas during pregnancy. Vigorous exercise increases our body temperature slightly but poses no threat to the foetus and good hydration is essential to help the foetus cool down and replace lost fluids, so drink plenty of water.

Although your body gets on with the job of supplying all your baby's needs, it needs conscious support from you. Take care of your body and your body will take care of the rest.