Bulletin of the World Health Organization

The worldwide incidence of preterm birth: a systematic review of maternal mortality and morbidity

Stacy Beck, Daniel Wojdyla, Lale Say, Ana Pilar Betran, Mario Merialdi, Jennifer Harris Requejo, Craig Rubens, Ramkumar Menon & Paul FA Van Look

Volume 88, Number 1, January 2010, 31-38

Table 2. Characteristics of the estimates and reports used in a systematic review to estimate the worldwide incidence of preterm birth, by region/country grouping

Variable Africa Asia Latin America and Caribbean Developed countriesa Total
Total 22 22 13 35 92
Study design
Cross-sectional 10 13 4 29 56
Cohort/controlled trial 3 5 2 1 11
Survey 9 4 7 5 25
Type of estimate
Population-based: national 0 6 3 23 32
Population-based: subnational 1 5 2 5 13
Facility-based 21 11 8 7 47
Estimate based on
Adolescents 1 1 0 0 2
Mixed ethnic group 0 1 0 0 1
Tribal group 0 2 0 0 2
Lower socioeconomic class 1 1 2 1 5
Not specific (general population) 18 15 11 29 73
Unspecified 2 2 0 5 9
Preterm birth definition
Less than 37 weeks gestation 17 16 11 31 75
Other 1 1 1 0 3
No definition reported 4 5 1 4 14
Diagnostic procedure
Ultrasound 2 1 0 2 5
Last menstrual period 2 4 0 6 12
Best obstetric estimate 6 0 6 0 12
Other 0 0 0 2 2
No method reported 11 18 7 25 61
Denominator used
Live births 3 8 2 16 29
Pregnancies 1 3 4 8 16
Deliveries 18 12 7 10 47


a Europe, North America (excluding Mexico), Australia and New Zealand comprise the developed countries category.

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