Did you know that some maternity units actually have more staff available during periods of full moon?

I've always been fascinated by the moon's effect on nature, so when a friend's wife conveyed to me what her midwife had told her during the birth of their daughter, I decided to find out more about childbirth, full moon and a possible link.

On speaking to various medical staff involved in natural childbirth, the first thing I learned was that expectant mothers often experience false signs of labor during full moon.

Contractions known as "Braxton Hicks" -- sometimes noticeable to the mother and sometimes not -- become more pronounced and many travel to the maternity unit in the belief that "it's time". Disappointed -- or perhaps relieved -- they return home, the pains having subsided and with no dilation of the cervix.

While these expectant mothers visiting the clinic with their mistaken signs of labor are part of the reason why extra staff are needed, the major difference is found in the number of women whose amniotic sac -- the water -- breaks.

Just as some women experience false labor pains, in cases where the water breaking marks the start of childbirth, full moon is the time when it's most likely to happen.

In order to discover for myself whether this could be true, I asked several female friends how their births had started. Those who responded with "the water breaking" were then asked the date of the birth. On checking this against a moon phase chart, I discovered that almost all had given birth on, or very close to, a full moon.

The theory is that the moon's gravitational pull effects the amniotic fluid in much the same way as it effects the water in the sea, rivers and even the water that's otherwise found in our bodies.

As a woman's body prepares for natural childbirth, the amniotic sac becomes distended so the point where it will easily burst if put under pressure. Under normal circumstances, the pressure of labor contractions bursts the sac. During a full moon, the pressure caused by the moon's effect on the water inside the sac can cause the same things to happen, but without the accompanying contractions.

When this happens, natural childbirth doesn't always move forward and with no other signs of labor present, the obstetrician may decide to induce the birth. During my own study of this phenomenon I found that of 8 women whose births started with the water breaking at full moon, 5 of them had no accompanying contractions.

A coincidence? Perhaps. But surely midwives wouldn't prepare themselves for an increase in natural childbirth activity if there wasn't some truth in this?

One midwife told me that when it comes to planning childbirth, full moons should always be looked for around the time of the expected delivery. If there's one within a few days either side, the chances are your baby will be born on that day.