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

In a double-blind trial at 11 Swedish clinics, 370 nulliparous women aged 18 to 31 were randomised to 10 mL of intrauterine mepivacaine 20 mg/mL or saline, instilled through a hydrosonography catheter two minutes before placement of a smaller-diameter IUD.

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

Fear of pain puts many young women off IUDs. This is a simple, cheap step that makes the procedure more tolerable, relevant to any clinician who fits or refers for IUDs.

Intrauterine instillation of mepivacaine, a local anaesthetic, reduced placement pain by about 15 points on a 100-point scale.
The trial used 10 mL of mepivacaine 20 mg/mL; it does not show whether lidocaine instillation works or at what dose.
Discuss pain relief openly when counselling nulliparous women about IUDs.
Pain was reduced, not abolished; the average score remained moderate.

Why it matters

Pain is a common reason young women decline the most effective reversible contraception.

The statistics, in plain English

A 15 mm difference on a 100 mm pain scale is generally above the threshold patients notice. The NNT of 15 means about one in 15 women moved from intolerable to tolerable pain; its 95% CI is 9 to 43.