Background <p>Most mothers in the UK are not meeting the breastfeeding recommendations set by the World Health Organisation (WHO, Breastfeeding - Recommendations. <a href="https://www.who.int/health-topics/breastfeeding#tab=tab_2">https://www.who.int/health-topics/breastfeeding#tab=tab_2</a>, 2023). Maternal obesity has variably been associated with lower initiation and shorter duration of breastfeeding, but few studies have examined the impact of maternal adiposity estimated from skinfold thicknesses.</p> Aim <p>To investigate the relationship between maternal adiposity and breastfeeding initiation and duration.</p> Methods <p>Data from 2,873 mother-offspring pairs in the Southampton Women’s Survey (SWS) mother-offspring cohort study were used to assess the relationship between a mother’s adiposity and breastfeeding initiation and duration. The exposure variables were body mass index (BMI) and body fat percentage, calculated from 4-site skinfold thickness measurements measured prior to conception. The outcome variables were breastfeeding initiation and duration. All analyses were adjusted for confounders identified using a Directed Acyclic Graph.</p> Results <p>After adjustment for confounders, no associations were found between maternal BMI (RR 0.99 per 5&#xa0;kg/m², 95% CI 0.97, 1.01) or body fat percentage (RR 0.99 per 5%, 95% CI 0.97, 1.00) and initiation of breastfeeding. After adjustment for confounders, amongst women who initiated breastfeeding, higher maternal BMI (β −0.09 SDs per 5&#xa0;kg/m², 95% CI −0.13, −0.04) and body fat percentage (β −0.10 SDs per 5%, 95% CI −0.16, −0.04) were associated with shorter breastfeeding duration.</p> Conclusions <p>In this study maternal adiposity had little impact on breastfeeding initiation but higher maternal adiposity was associated with shorter breastfeeding duration. This study suggests that more support should be given to mothers with overweight and obesity to promote longer duration of breastfeeding.</p>