Seasonality in twin births.
Twin births have occurred seasonally in England and Wales since 1940. The probability of a twin birth is highest in November and lowest in May. The difference between the two probabilities is of the order of seven per cent.
D001723:Birth Rate; D004739:England; D005260:Female; D006801:Humans; D011247:Pregnancy; D012621:Seasons; D014427:Twins; D014852:Wales