WHO 1999a.

Methods	Prospective longitudinal study
Participants	4118 breastfeeding, literate women in China, India, Australia, Nigeria, Chile, and Sweden. 3422 completed the study
Interventions	Non‐LAM, infant feeding practices, menstrual status and pregnancy recorded. Participants kept a daily record
Outcomes	Censored CPR 0.9 ‐ 1.2 (2831 ‐ 2969 WMAC) depending on which definition of menstruation was used
Notes	4 different definitions of menstruation used; 696 women left the study (150 had only 1 unconfirmed bleeding, 546 had no bleeding)
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	D ‐ Not used

CMR: cumulative menstruation rate at 6 months according to life tables
 CPR: cumulative pregnancy rate at 6 months according to life tables
 EC: emergency contraception
 IUD: intrauterine device
 LAM: lactational amenorrhoea method
 RCT: randomised controlled trial
 WMAC: woman months accumulated