Design: Multicentre, double-blind, randomised, placebo-controlled trial
Population: 370 nulliparous women aged 18–31 having a smaller-diameter IUD placed, Sweden
Primary outcome: Pain during IUD placement, 100-mm visual analogue scale
Effect: 43.8 vs 58.6 mm; difference 14.8 mm (95% CI 10.0–19.6)

A multicentre double-blind placebo-controlled trial in 11 Swedish outpatient clinics randomised 370 nulliparous women aged 18–31 having a smaller-diameter levonorgestrel or copper IUD fitted. Each received 10 mL of mepivacaine 20 mg/mL or saline instilled into the uterus through a hydrosonography catheter, 2 minutes before placement.

Mean pain during placement was 43.8 mm with mepivacaine and 58.6 mm with saline on a 100-mm scale, a difference of 14.8 mm (95% CI 10.0–19.6). Tolerable pain was reported by 98.3% against 91.4% (RR 1.08), a number needed to treat of 15.

This is a simple, cheap step tested in the group that finds placement hardest. Pain still averaged above 40 mm, so it reduces rather than removes discomfort, and the result applies to nulliparous women and narrower insertion tubes. Fear of pain is a common reason women decline an IUD, so this is worth discussing at counselling where local anaesthetic and a catheter are available.

Consider intrauterine local anaesthetic instillation for nulliparous women having an IUD fitted.
The tested regimen was 10 mL of mepivacaine 20 mg/mL via a hydrosonography catheter, 2 minutes before placement.
Tell women it reduces pain but does not abolish it: mean scores stayed above 40 out of 100.
Check for local anaesthetic allergy before instillation, as the trial excluded it.

Why it matters

Pain is a common reason women turn down the most effective reversible contraception.

The statistics, in plain English

A 15-mm drop on a 100-mm scale is around the size many patients notice as a real difference, and the interval (10 to 20 mm) stays clear of zero. A number needed to treat of 15 means about one extra woman in 15 found placement tolerable because of the anaesthetic.