A woman told her baby is measuring large has already had her birth changed, whatever you decide next. So the words matter, and three of them help.
First, give the error honestly: a third-trimester estimate is commonly out by 10% or more in either direction, so an estimate above the 90th centile frequently belongs to a baby who is not. Second, separate the estimate from the decision — an estimated weight is one input into a conversation about mode of birth, not an instruction. Third, name what actually predicts shoulder dystocia, because that is what she is frightened of: diabetes, previous shoulder dystocia and instrumental delivery carry more weight than an ultrasound number alone.
And document the conversation, including the estimated weight, the uncertainty you conveyed, and the plan she agreed. If the birth is later reviewed, what was said about the scan will matter as much as what the scan said.
- State the margin of error out loud — an estimate near the 90th centile is frequently wrong in both directions
- Frame the estimate as one input into a shared decision, not as a finding that dictates delivery mode
- Name the stronger predictors of shoulder dystocia: diabetes, previous dystocia, instrumental delivery
- Avoid the word macrosomia with a patient unless the birthweight is known; it frightens more than it informs
- Record the estimated weight, the uncertainty conveyed and the agreed plan in the notes
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for obstetrics & gynaecology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free