Biochemical osteomalacia during pregnancy or lactation: an observational study in Sweden.

BACKGROUND: Studies of osteomalacia during pregnancy and lactation are scarce. This is likely due to the hazards of performing X-ray in pregnancy, the inconvenience of the gold standard diagnostic procedure of bone marrow biopsy with histomorphometry and the lack of these resources in maternity health care. Another important reason is the lack of international consensus on how to diagnose osteomalacia clinically. Osteomalacia needs attention due to the limited number of modern studies on its prevalence and globalization, especially in some populations where migration to high latitudes with poor light conditions, as in Scandinavia, can heighten its prevalence. The aim of this study was to determine the prevalence of biochemical osteomalacia during pregnancy or lactation among Somali and Swedish women living in Sweden. METHODS: This was an observational cohort study of 71 Swedish and 52 Somali pregnant or lactating women. Blood samples, self-report questionnaires and physical examination data were collected in late spring. The diagnostic criteria for biochemical osteomalacia were serum levels of a 25-hydroxy vitamin D3 (25(OH)D) concentration < 30 nmol/L, a parathyroid hormone (PTH) concentration > 6.9 pmol/L and an alkaline phosphatase (ALP) concentration > 1.8 ukat/L. The presence of clinical symptoms (grip weakness, leg weakness, a positive Trendelenburg test, fatigue, and pain) was used to reaffirm the diagnosis. RESULTS: The diagnostic criteria for biochemical osteomalacia were met by one Swedish woman 1/71 (1.4%) and 18/52 (34.6%) of all Somali women, of whom 1/71 (1.4%) and 16/52 (30.8%), respectively, had signs or symptoms reaffirming the diagnosis. CONCLUSIONS: Women of Somali origin living at high altitudes are at high risk for vitamin D deficiency osteomalacia, but Swedish women may also suffer from this disease. These findings call for further studies on the prevalence of vitamin D deficiency, especially among groups at risk of vitamin D deficiency, because of the hidden disease burden. Establishing internationally accepted criteria for a noninvasive clinical diagnostic procedure for osteomalacia is imperative. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02922803. Date of registration: September 28, 2016.