Maternal pre-pregnancy BMI is associated with the duration of exclusive breastfeeding in SCAPIS – Umeå

Background and objectives: Breastfeeding is recognized as the optimal nutrition for infants and exclusive breastfeeding (EBF) for six months is recommended by the WHO. Breastfeeding is also associated with maternal health benefits, such as decreased risk of breast- and ovarian cancer and diabetes type 2. Excess weight is a common risk factor for those diseases, and higher pre-pregnancy BMI (preBMI) is negatively associated with breastfeeding related outcomes. Early adulthood weight change pre-pregnancy (preWC) has however, to our knowledge, not previously been studied. The aim was to determine the impact of maternal preBMI and preWC on EBF of the first child in a Swedish setting. Methods: Data was derived from the Umeå sub-cohort of the Swedish Cardiopulmonary Bioimage study (SCAPIS), a population-based cohort study conducted 2016–2018. Parous women aged 50–64 years, reported retrospectively via questionnaires, their duration of EBF in months. The relationship between retrospectively self-reported preBMI and preWC (from 20 years of age until pre-pregnancy), respectively, and EBF of the first child was explored with linear regression reported as β (95% Confidence Interval (CI)) and logistic regression reported as Odds Ratio (OR) (95% CI). Models were adjusted for age at first delivery (years) and education (≤12 years/>12 years). Results: In our sample, including 980 women who initiated any breastfeeding, mean (SD) age at first delivery was 26.0 (4.6) years, mean preWC was 1.1 (5.4) kg and mean preBMI was 21.6 (2.9) kg/m2. Breastfeeding was initiated by 92%. Mean duration of EBF was 4.8 (2.8) months. PreBMI was significantly inversely associated with duration of EBF (β = –0.076 (–0.145; –0.008)). Among those reporting any EBF, the OR of EBF > two months were 0.92 (0.86; 0.98) per increase in preBMI unit. PreWC was not associated with EBF. Age consistently showed a significant positive association with EBF, while the association with education was positive but not consistently significant. Discussion: In line with previous research preBMI was inversely related to EBF duration, while the novel exposure preWC was not related. Still, to increase the duration of EBF, support should be focused on mothers with higher preBMI and younger mothers.