The influence of lactation and its duration on bone mineral density in pregnancy and postpartum: A systematic review with meta-analysis.

Abstract

There is a plethora of research on the association of parity and duration of lactation with bone mineral density (BMD) during and after pregnancy. However, there are no consensus conclusions on the impact of the duration of lactation on BMD. The aim of this study was to examine the effect of pregnancy, and the duration of lactation on BMD during pregnancy, postpartum phase and 12 months post-delivery. The search terms 'parity' 'lactation' 'BMD' were searched for using PubMed, CINAHL, SCOPUS and EMBASE databases in English language. Two independent reviewers assessed the quality of the included studies using Critical Appraisal Skills Program (CASP) appraisal tool and extracted data on BMD (g/cm2) in Excel. A meta-analysis was conducted with a random effect model using Cochrane Review Manager (Rev 5.4) to analyse the outcome. Heterogeneity was assessed with Chi Squared and I2 test. The duration of lactation was grouped into short lactation duration (SLD), ≤4 months and longer lactation duration (LLD)>6 months. Twenty-one studies were included in this review with four studies included in the meta-analysis. BMD reduced during pregnancy and lactation. Recovery and net gains in BMD followed weaning. However, at 12 months postpartum, women in the LLD group had significant losses at the lumbar spine while those in the SLD recovered BMD. Between the SLD and LLD groups, the change in BMD was not significant 0.48g/cm2 (95% CI -0.14, 1.10, p=0.13). BMD losses were greater in primiparous women than multiparous women. Women who breastfed for >6 months had significantly reduced BMD. However, compared to women that breastfed for a ≤4 months there was no significant change in BMD. Further investigation is needed to clarify the association between lactation and BMD in a postpartum population in those women extending breastfeeding beyond one year.