• Petteri Oura, Markus Paananen, Juha Auvinen, Jaakko Niinimäki, Maarit Niinimäki, Jaro Karppinen, and Juho-Antti Junno.
• Center for Life Course Health Research, Faculty of Medicine, University of Oulu Research Unit of Medical Imaging, Physics and Technology, Faculty of Medicine, University of Oulu.
• Spine. 2018 Sep 15; 43 (18): E1102-E1108.

Study DesignA population-based birth cohort study.ObjectiveTo investigate the association between gravidity, parity, and vertebral geometry among middle-aged women.Summary Of Background DataVertebral size is a recognized determinant of vertebral fracture risk. Yet, only a few lifestyle factors that influence vertebral size are known. Pregnancy is a labile period that may affect the maternal vertebral size or shape. The lumbar lordosis angle is permanently deepened by pregnancy, but it remains unclear whether vertebral shape or size contribute to this deepened angle.MethodsWe aimed to investigate whether gravidity and parity were associated with vertebral cross-sectional area (CSA) and height ratio (anterior height to posterior height) among 705 middle-aged women from the Northern Finland Birth Cohort 1966. We measured the corpus of their fourth lumbar vertebra using magnetic resonance imaging of the lumbar spine at the age of 46. Gravidity and parity were elicited using a questionnaire also at the age of 46. Linear regression analysis was used with adjustments for body mass index, vertebral CSA (height ratio models), and vertebral height (CSA models). We also ran a subgroup analysis that did not include nulliparous women, and we compared nulliparous women with grand multiparous women.ResultsThe models found no statistically significant associations between the predictors and outcomes. Crude and adjusted results were highly similar, and the subgroup analyses provided analogous results.ConclusionPregnancy, or even multiple pregnancies, do not seem to have long-term effects on vertebral geometry. In order to enhance the prevention of vertebral fractures, future studies should aim to reveal more lifestyle determinants of vertebral size.Level Of Evidence3.

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