Quantitative ultrasonometry during pregnancy and lactation: a longitudinal study

This study describes bone mass changes during pregnancy and lactation measured by a special ultrasound method. Pregnant women showed a decrease of bone mass followed by a stable bone mass while breast-feeding afterwards. Later in life, there is a recovery of bone mass loss.

The aim of this study was to evaluate bone changes during pregnancy using the radiation-free method of quantitative ultrasonometry (QUS).

One hundred twenty-five pregnant women who underwent prenatal care were included in this study. Ultrasound measurement of the calcaneus was performed in each trimester and then 6 weeks, 3 months, and 1 year postpartum. The calcaneal QUS measurements were carried out using the Achilles plus device (GE/Lunar Corporation, Madison, WI). Three ultrasound variables were measured: speed of sound (SOS, m/s), broadband ultrasound attenuation (BUA, dB/MHz), and the "stiffness index" (expressed as the percentage of the mean value in young adults). SOS and BUA raw data result in the t-score and z-score.

A complete panel of six measurements was acquired over the time period in 101 patients (80.8%). Forty-two percent of the included patients were primipara, while 58% had given birth to at least one child (47%) previously. There was a statistically significant change of the t-score (tv = 2.14, p = 0.035) and the stiffness index (tv = 2.46, p = 0.016) from the second to the third trimester, followed by a plateau during lactation. Interestingly, the t-score remained stable during lactation, regardless of the duration of lactation (<3 months, 3-6 months, and >6 months).

Young primiparas who had a sedentary adolescence were at the highest risk of bone loss during pregnancy. Bone loss that occurred during pregnancy was typically recovered later on, based on unknown molecular and biochemical mechanisms that must be elucidated with further studies.