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

Upon enrollment, gestational history, maternal clinical conditions, drug therapy, demographic and anthropometric parameters will be recorded, and specific questionnaires developed by the Fragility Fracture Observatory (OFF) will be administered. These questionnaires aim to assess all risk factors that could lead patients to have a fracture during pregnancy and to evaluate both dietary habits (specifying the type of food with high, medium and low calcium content with relative portions and frequencies) and adherence to the Mediterranean diet (determining, based on the total score, whether the dietary calcium intake is sufficient to support the physiological adaptation of the pregnant woman, who must provide adequate amounts of calcium for the development of the fetal skeleton and the correct growth of the newborn during breastfeeding).

The first questionnaire is divided into two sections: one specifically for "calcium intake" and the other dedicated to assessing the woman's eating habits (Predimed Questionnaire) during pregnancy, which measures portion sizes and the frequency of nutrient intake through food and beverages.

The second questionnaire, AFEF (Fracture Risk Algorithm for Women of Childbearing Age), specifically assesses fracture risk during pregnancy. It collects anthropometric information (weight and height), medical history and personal and family medical history, lifestyle (number of cigarettes smoked daily), and any therapies undertaken before and during pregnancy.

An assessment of bone health using ultrasound densitometry using REMS technology, integrated into the EchoStation device (Echolight Spa, Lecce, Italy), is performed during the third trimester checkup.

The importance of using REMS ultrasound lies in its complete absence of ionizing radiation, ease of use, and rapid scanning. Thanks to an innovative parameter called Fragility Score (FS), intrinsically correlated with bone quality and independent of BMD, REMS allows for the assessment of bone fragility and its resulting fracture risk, representing a useful diagnostic tool also in predicting the risk of fragility fractures. All of this makes this method absolutely compatible and optimal for routine monitoring of bone health and fracture risk in women during pregnancy.

The objectives of the REMS ultrasound technology are:

• To obtain a quantitative and qualitative assessment of bone status at the proximal femur level in all patients enrolled in the study, stratifying them into two groups based on the BMD values obtained (normal and reduced).
• To evaluate, using the REMS-based Fragility Score (FS), the risk factors associated with changes in bone fragility, and to identify the cut-off for the FS measured at the femoral neck specifically for pregnant women.

The EchoStation device (manufactured by Echolight Spa) consists of a medical-grade cart, which houses a panel PC, a medical-grade keyboard and mouse, a main unit, and a convex probe operating at a nominal frequency of 3.5 MHz. The EchoStudio software, integrated into the EchoStation device, dedicated to assessing bone health, allows for the automatic calculation of the same diagnostic parameters provided by a DEXA scan (Bone Mineral Density (BMD), T-score, and Z-score) from unfiltered ultrasound radiofrequency signals acquired during an ultrasound scan of a reference anatomical specimen (femoral neck). The ultrasound signals of the bone region in question are automatically processed and compared with reference spectral models previously derived from healthy and osteoporotic patients in order to assess the subject's bone mineral density; and with previously derived reference spectral models from patients with and without fractures to assess bone fragility and related fracture risk using the innovative FS parameter.

This approach, unlike conventional ultrasound, maximizes the information gathered from the acquired signals, while the reconstructed B-mode ultrasound images serve as a guide for the correct identification of the bone being examined. The simultaneous acquisition of multiple ultrasound signals for each frame is integrated with the ultrasound imaging, which also serves as a guide for identifying the region of interest (ROI) within the bone being examined, providing a solid and reliable statistical basis for subsequent analyses.

Women between the 35th and 41st week of gestation (inclusive) will undergo ultrasound examination of the proximal femur using an EchoStation ultrasound system (Echolight Spa, Lecce, Italy) with a convex probe operating at a nominal frequency of 3.5 MHz. Trained operators will follow a standard procedure. Specifically, a 40-second software-guided ultrasound scan will be performed with the ultrasound probe positioned at the head-neck axis of the femur. The probe will be positioned parallel to the long axis of the femur, and the transducer focus and scan depth will be appropriately set to place the femoral neck interface in the focal zone of the beam and in the central portion of the image. The software will then automatically analyze the unfiltered ultrasound signals, identifying the bone interface and ROI; the resulting signals will be processed and, after this automatic process, the diagnostic report will be produced.

Inclusion criteria

• Signed informed consent
• Willingness to participate in the study and ability to complete the study questionnaires
• Women between 35 and 41 weeks of gestational age at the time of study inclusion
• Singleton or twin pregnancy (dichorionic or monochorionic)
• Age between 30 and 45 years at the time of study recruitment
• No history of recent or previous bone fractures or traumatic fractures, and no motor disabilities (in the mother).
• Absence of a diagnosis of osteopenia or osteoporosis according to the criteria of the Italian Society for Osteoporosis, Mineral Metabolism and Bone Diseases (SIOMMMS).
• No intake of vitamin D or other medications during pregnancy.
• Absence of current or previous conditions that could potentially interfere with bone metabolism (e.g., thyroid, kidney, or liver disease).
• 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:

• Failure to sign the informed consent form
• Poor compliance and/or inability to complete the study questionnaires
• Women with previous or newly diagnosed comorbidities during pregnancy
• Age <30 and >45 years
• Previous diagnosis of osteopenia or osteoporosis according to the criteria of the Italian Society for Osteoporosis, Mineral Metabolism and Bone Diseases (SIOMMMS)
• BMI <18.5 or >34