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Centre for Evidence-
Based Medicine

Example NNTs - Obstetrics-Gynecology

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates % NNT (95% CI)
CER EER
Excessive uterine bleeding1 Levonorgestrel intrauterine system vs. control group Number of women canceling their decision to have a hysterectomy 6 months 14 64 2 (1 to 4)
First-stage labor pain2 Intracutaneous injections of sterile water vs. placebo Labor pain was measured with a 10-cm visual analog scale (0 cm = no pain; 10 cm = worst conceivable pain) 90 minutes 25 59 3 (2 to 13)
Subcutaneous injections of sterile water vs. placebo 25 52 4 (3 to 82)
Breech presentation3 Planned cesarean section vs. planned vaginal birth (control) Perinatal or neonatal mortality or serious neonatal morbidity 6 weeks 5.0 1.6 30 (20 to 54)
Perinatal or neonatal mortality 1.3 0.3 104 (54 to 416)
Serious neonatal morbidity 3.8 1.4 41 (26 to 90)

References

  1. BMJ 1998 Jul 25;317(7153):235-40
  2. Br J Obstet Gynaecol. Jul 1999; 106: 633-7
  3. Lancet. Oct 21, 2000; 356: 1375-83