The influence of lactation on BMD measurements and TBS: a 12-month follow-up study.

Although lactation is associated with transient bone loss and body weight changes, the unchanged TBS could highlight a limited effectiveness in detecting dynamic bone properties in the first year postpartum.

PURPOSE: To evaluate trabecular bone score (TBS) and bone mineral density (BMD) in postpartum women.

METHODS: This was a 12-month prospective cohort study with 40 lactating postpartum women and 44 non-pregnant women. The inclusion criteria were as follows: aged between 18 and 35 years old, an uncomplicated term (≥37 weeks) pregnancy with a single fetus, and no intention of becoming pregnant within 12 months. BMD measurements, including spine, hip, forearm and whole body, were performed by DXA at four different time points after delivery: (1) 1st month, (2) 3rd-4th month, (3) 6th-9th month, and (4) ≥ 12th month postpartum.

RESULTS: BMD measurements showed a statistically significant decrease at spine (1.134 vs. 1.088 g/cm2 , p < 0.01), femoral neck (0.988 vs. 0.946 g/cm2 , p < 0.01), total femur (0.971 vs. 0.933 g/cm2 , p < 0.01), and whole body (1.132 vs. 1.119 g/cm2 , p = 0.03) at the 2nd assessment (peak of lactation). There was early spinal recovery after the 3rd assessment with complete recovery in all skeletal sites. Although it has had significant weight loss (67.3 vs. 63.2 kg, p < 0.01) and body mass index reduction (25.2 vs. 23.4, p < 0.01), there was significant increment of spine BMD (1.134 vs. 1.165 g/cm2 , p < 0.01) after 12-month follow-up. The TBS did not change over time.

CONCLUSIONS: Although lactation is associated with transient bone loss and body weight changes, the unchanged TBS could highlight a limited effectiveness in detecting dynamic bone properties in the first year postpartum.