According to researchers from Vienna, statistics dating as far back as 1967 show that if you're born in July you'll have 13% fewer children than if you were born in December. At least that's the case in the northern hemisphere, as when the researchers checked out the birth patterns in New Zealand - where they have summer when it's winter here and vice versa - they found the opposite was the case.
Perhaps weather conditions have something to do with it, they suggest, or it may be that the eating patterns of the mother might affect the development of the fertility of their unborn child. But interestingly, when the same researchers looked at statistics in Vietnam, they noticed - like in New Zealand - that the women born in July (during the rainy season, in other words) had more babies than those born in January.
The researchers also discovered men who have the most children are born in the spring, with those born in autumn having the least. It just goes to show that our knowledge of how the human body works is far from complete, despite the massive advances made by medical science.
Many other things can affect your fertility other than the month you were born in, some of which you have more control over - heavy drinking, for instance, can disrupt your cycle, which affects your fertility.
If you're from a large family, was your mum born in the winter?