Comparison of Bone Mineral Density in the Third Trimester Between Women in Singleton and Twin Pregnancies Using Questionnaires and REMS Densitometric Examination

INCLUSION CRITERIA 1. Signed informed consent 2. Willingness to participate in the study and ability to complete the study questionnaires 3. Women between 35 and 41 weeks of gestational age at the time of study inclusion 4. Singleton or twin pregnancy (dichorionic or monochorionic) 5. Age between 30 and 45 years at the time of study recruitment 6. No history of recent or previous bone fractures or traumatic fractures, and no motor disabilities (in the mother). 7. Absence of a diagnosis of osteopenia or osteoporosis according to the criteria of the Italian Society for Osteoporosis, Mineral Metabolism and Bone Diseases (SIOMMMS). 8. No intake of vitamin D or other medications during pregnancy. 9. Absence of current or previous conditions that could potentially interfere with bone metabolism (e.g., thyroid, kidney, or liver disease). 10. Women of normal weight or with class I obesity (BMI between 18.5 and 34). EXCLUSION CRITERIA Patients will not be included in the study if at least one of the following exclusion criteria is met: 1. Failure to sign the informed consent form 2. Poor compliance and/or inability to complete the study questionnaires 3. Women with previous or newly diagnosed comorbidities during pregnancy 4. Age \<30 and \>45 years 5. Previous diagnosis of osteopenia or osteoporosis according to the criteria of the Italian Society for Osteoporosis, Mineral Metabolism and Bone Diseases (SIOMMMS) 6. BMI \<18.5 or \>34