How a number goes wrong on its way to you
Three real examples, from good sources, of a figure that changed meaning between the original study and the place most people read it.
Every number in this stage passed through at least one pair of hands before it reached you. Here is what can happen on the way. None of these is a scandal. All of them are ordinary, and all of them would change what you believed.
Example one: a subgroup becomes the whole group. A well-known systematic review of women's expectations of pain relief describes a 1998 study of 324 women as showing that 36% anticipated suffering extreme pain, and then gives a much higher figure for how many actually experienced it.
Go back to the original. It reports that 45% of first-time mothers and 36% of women who had given birth before anticipated extreme pain. The review took the second-baby figure and presented it as though it described the whole sample. The higher figure it quotes for what women actually experienced does not appear in the original study at all, so this guide does not publish that number in any form.
The difference is not trivial. If you are expecting your first baby, the figure that describes women like you is 45%, not 36%, and the review would have told you the wrong one.
The same review also attributes a set of figures about pain expectations to a paper that was actually about stereotypes of pregnant women. Those numbers are not published here either.
To be fair to that review, its central conclusion is sound and this guide relies on it: Women may have ideal hopes of what they would like to happen with respect to pain relief, control and engagement in decision-making, but experience is often very different from expectations. Antenatal educators need to ensure that pregnant women are appropriately prepared for what might actually happen to limit this expectation-experience gap and potentially support greater satisfaction with labour.
A paper can be right about the big thing and wrong about a small number. Both are true at once.
Example two: the text and the table disagree. A systematic review of labor durations gives one 95th centile in its running text for first-time mothers starting from 6 cm, and a slightly lower one in its own table a few pages away. This guide publishes the table value, 9.3 hours, and would rather say about 9 hours than pretend to a precision the paper does not have.
Example three: the document is no longer the document. The 2014 American consensus statement on preventing the first cesarean is quoted in articles, classes and hospital policies to this day. ACOG has withdrawn it. Its page reads Withdrawn Clinical Document
, and it was replaced in January 2024. If someone quotes a labor guideline to you, the date is part of the quotation.
What to do with this. Not distrust everything. The fix is small and it works: when a number matters to your decision, ask where it comes from, and ask whether it describes women like you. Those 46 women in the focus-group study asked for exactly this, presented kindly and with real frequencies. They were right to.
"Was that figure for first babies or for later ones?"
"What year is that guideline, and is it still current?"
"How many women were in that study?"