**Background:** Anaemia, defined by low red blood cell count, affects over half a billion women of reproductive age globally, with the highest burden in low- and middle-income countries (LMICs). Lactating women are considered particularly vulnerable due to physiological iron demands and nutritional challenges. While previous studies have examined anaemia in specific countries, few have compared prevalence and determinants between lactating and non-lactating women across multiple LMICs. This study aimed to fill that gap using nationally representative data from 46 countries.
**Methods:** The study used the most recent Demographic and Health Surveys (DHS) from 46 LMICs conducted between 2010 and 2020. A total of 185,330 lactating and 827,501 non-lactating women of reproductive age (both non-pregnant) who had given birth in the preceding 5 years were included. Anaemia was defined as altitude-adjusted haemoglobin <12 g/dL. Multilevel multivariable logistic regression was used to identify factors associated with anaemia, accounting for the hierarchical structure of DHS data (individuals nested within communities). Adjusted odds ratios (AOR) with 95% confidence intervals (CI) and p<0.05 were reported.
**Key Results:** The overall prevalence of anaemia was 50.95% (95% CI 50.72–51.17) among lactating women and 49.33% (95% CI 49.23–49.44) among non-lactating women. In the combined model, lactating women had 1.11 times higher odds of anaemia compared to non-lactating women (AOR=1.11, 95% CI 1.10–1.13). Country-level prevalence varied widely: among lactating women, from 11.71% in Rwanda to 60.49% in India; among non-lactating women, from 13.02% in Guatemala to 63.43% in Maldives.
Factors significantly associated with higher odds of anaemia in both groups included: lower education (e.g., no education vs. higher: AOR=1.42 [1.36–1.48] for lactating, 1.25 [1.23–1.28] for non-lactating), poorest wealth index (vs. richest: AOR=1.76 [1.70–1.83] for lactating, 1.66 [1.64–1.69] for non-lactating), larger family size (>10 vs. ≤5: AOR=1.23 [1.18–1.28] for lactating, 1.45 [1.42–1.48] for non-lactating), unimproved drinking water (AOR=1.97 [1.94–1.99] for lactating, 1.45 [1.43–1.46] for non-lactating), history of terminated pregnancy (AOR=1.05 [1.02–1.09] for lactating, 1.07 [1.05–1.08] for non-lactating), and not using contraceptives (AOR=1.25 [1.22–1.28] for lactating, 1.14 [1.13–1.15] for non-lactating). Media exposure was protective (AOR=0.95 [0.93–0.98] for lactating, 0.94 [0.93–0.96] for non-lactating).
Factors significant only in lactating women included: unimproved toilet facility (AOR=1.97 [1.94–1.99]), fewer than 4 ANC visits (AOR=1.08 [1.06–1.11]), no PNC (AOR=1.08 [1.06–1.11]), home delivery (AOR=1.05 [1.02–1.08]), and no iron supplementation (AOR=0.08 [0.05–0.12] for yes vs. no). Smoking was significantly associated with anaemia only in non-lactating women (AOR=1.89 [1.83–1.94]).
**Clinical Implications:** The study confirms that anaemia remains a severe public health problem in LMICs, affecting nearly half of all reproductive-age women, with lactating women at slightly higher risk. The strong associations with poverty, low education, poor water/sanitation, and limited healthcare access highlight the need for multi-sectoral interventions. Improving access to clean water and sanitation, promoting family planning, ensuring adequate ANC/PNC and iron supplementation, and targeting disadvantaged communities are critical strategies. The findings support the WHO Global Nutrition Target to reduce anaemia by half by 2030, but underscore that progress must address both individual and community-level determinants.