Should pregnant women routinely be offered flu jabs?

For babies born in February, the latter stage of pregnancy falls in the peak flu season

It is no revelation that babies conceived in May are more likely to be born prematurely.

The trend has been well known for some time and the assumption was that social or lifestyle factors that might be associated with race, say, or class, were the likeliest cause.

Now, however, a vast study of nearly 1.5 million children and 650,000 mothers has yielded a quite different explanation. In fact, the spike is because, with a due-date in February, the latter stage of pregnancy falls in the peak flu season – and a severe bout is enough to trigger a premature delivery.

Armed with such information, the debate now moves on to whether pregnant women should be routinely offered a flu jab. But it is worth taking a moment to acknowledge another triumph for clear-eyed, large-scale number-crunching in exposing patterns that, with assumptions alone, we would otherwise miss.