Analysis methods and key findings of included studies
| First author and year of publication | Lactational amenorrhoea outcomes/indicators assessed among adolescents | Analysis method | Findings |
| Nath et al 46 1993 | Median duration of postpartum amenorrhoea in months, median duration of breast feeding in months, percentage of females resuming menses before fixed periods since birth (3, 6, 12, 18 months) | Descriptive life table analysis (disaggregated by age group), multivariate hazard models modelling return to menses | Median duration of postpartum amenorrhoea among women <20 years: In Assam 9.9 months (compared with 20–25 years: 9.0 months; 25–30 years: 10.0 months; >30 years: 12.1 months). In Uttar Pradesh 3.5 months (compared with 20–25 years: 4.9 months; 25–30 years: 8.2 months; >30 years: 12.1 months). Percentage returning to menses at 6 months: Assam <20 years: 32.2%, 20–25: 28.2%; 25–30: 30.9%; >30: 26.3%. Uttar Pradesh: <20: 63.6%; 20–25: 56.6%; 25–30: 48.6%; >30: 42.7%. Multivariate models (adjusted for sex of child, literacy, caste, income group and breastfeeding duration, but not for parity): Compared with women >30 years: In Assam, women <20 years were 34%–38% more likely to return to menses and the effect estimates were similar between age group <20 years and age groups 20–25 and 25–30 years. In Uttar Pradesh, women <20 were 55%–56% more likely to return to menses; the effect estimates for age group 20–25 was 29%–31% and for 25–30 was 12% (there was a trend) |
| Bhattacharya et al 45 1995 | Median duration of postpartum amenorrhoea in months, percentage amenorrhoeic at 3, 6, 12 to 18 months since birth | Descriptive analysis | Mediation duration of postpartum amenorrhoea among <20 years is 3.45 months, n=452. 20–25 years: 4.87 months (n=1102); 25–30: 8.24 months (n=974), ≥30: 12.11 months (n=1174). Proportion of women returning to menses since birth among <20 year olds: at 3 months 51.8%; 6 months 63.6%; 12 months 85.0%; 18 months 93.4%. These percentages were lower than in all older age categories—there appears to be a trend of lower percentage returning to menses with increasing age at all four cut-offs (statistical tests not carried out) |
| Haggerty and Rutstein52 1999 | Median duration of postpartum amenorrhoea in months | Descriptive analysis | Median duration of postpartum amenorrhoea: Sub-Saharan Africa: range in 15–19 group: 7.2 months (Kenya) to 15.9 months (Nigeria). In 14 of the 18 countries, there was a clear trend of increasing duration of amenorrhoea with each older age group (the four exceptions were Kenya, Namibia, Nigeria, Senegal—all of which have a U-shape by age group, with highest levels among women 35+). Near East/North Africa: range in 15–19 group: 2.8 months (Morocco) to 5.8 months (Egypt). In 3 of the 4 countries, there is a U-shape (longest duration among 35+), except in Jordan where there was clear trend of increasing duration of amenorrhoea with each older age group with the highest level at age 25–34 years. Asia: range from 2.2 (Pakistan) to 8.9 (Nepal). Latin America/Caribbean: range from 2.2 (Brazil) to 8.9 (Haiti). Sub-Saharan African countries have the longest durations of amenorrhoea—14 of 18 countries had medians longer than a year. The Near East/North Africa region had the shortest durations, from 4 to 6 months. The largest variability was documented in the Latin America/Caribbean region where median durations ranged from 4 or 6 months to 11 months. Across the four regions examined, the increase in duration of postpartum amenorrhoea with increasing age group was most notable in Sub-Saharan Africa |
| Rahman et al 47 2002 | Median duration of lactational amenorrhoea in weeks | Descriptive (analytical) analysis | Median duration of lactational amenorrhoea among mothers <20 years (n=23) was 19.71 weeks. Among women 21–25 years, it was 26.57 weeks (n=44), ≥25 years (n=28) 20.8 weeks. Wilcoxon statistic p value ‘not significant’ across age categories |
| Rahman et al, 2005 | Postpartum amenorrhoea as a reason for non-use of contraceptives (modern/traditional) | Descriptive analysis | Postpartum amenorrhoea as a reason for non-use of contraceptives (modern/traditional) was 13.2% (146 of 1104 adolescents who were not using contraceptives at the time of survey). Multiple reasons were allowed |
| Audu et al 50 2006 | Ever-use of lactational amenorrhoea as a family planning method | Descriptive (analytical) analysis | Percentage of women reporting ever-use of lactational amenorrhoea method for family planning was 15–19 years: 5.0%; 20–24 years: 10.0%; 25–29 years: 7.2%; 30–34 years: 23.3%; 35–39 years: 17.9%; and 40–45 years: 21.3%. P value of the differences=0.00004 |
| Türk et al 49 2010 | Percentage of females who consider themselves users of lactational amenorrhoea for family planning | Descriptive (analytical) analysis | Percentage of females who considered themselves users of lactational amenorrhoea for family planning was 70% of those ≤19 years old (n=10), compared with 33% of those 20–29 years old (n=135) and 30% of those ≥30 years old (n=43); p value 0.001. However, many of the women who considered themselves users of lactational amenorrhoea method also reported having menses (28 of 64 users, not disaggregated by age group) |
| Singh et al 51 2012 | Median duration of postpartum amenorrhoea in months | Survival analysis (adjusted Cox proportional hazards) | Median duration of postpartum amenorrhoea among girls <15 years at time of marriage: 6.4 months, 15–20 years: 5.8 months, 20–25 years: 5.1 months, 25–30 years: 4.5 months and ≥30 years: 4.3 months (log-rank test p value<0.01). In multivariate Cox regression with the outcome of duration of postpartum amenorrhoea (included variables were duration of breast feeding, age at marriage, sex of index child, survival of index child, use of contraceptives, place of residence, husbands education, family income), the relative risk for variable of ‘age (years) at marriage of wife’ was 1.011 (95% CI 0.994 to 1.029), meaning that there was no association after other factors were accounted for. However, it is unclear whether the variable age in this model was categorised (<15, 15–20, 20–25, 25–30, >30) or used continuously (in years) |
| Kaplanoglu et al48 2015 | Percentage using lactational amenorrhoea as a family planning method (not sure whether at time of survey or ever during postpartum follow-up), contraceptive failure rate (% of adolescents in the sample who had unintended pregnancies in the first year) | Descriptive analysis | Percentage using lactational amenorrhoea as a family planning method: 50.6% among those 10–19 years old compared with 33% among women 20–35 years. Lactational amenorrhoea was the most preferred method of contraception in this study (no quantitative indicators shown). Contraceptive failure among adolescents was 2.37% in the first year post partum (12 unintended pregnancies among 506 adolescents in sample), compared with 2.0% in older age group |