BMC PREGNANCY AND CHILDBIRTH BMC PREGNANCY AND CHILDBIRTH Development and psychometric properties of the maternal ambivalence scale in spanish women Martín-Sánchez Magdalena Belén Martínez-Borba Verónica Catalá Patricia Osma Jorge Universidad de Zaragoza Peñacoba-Puente Cecilia Suso-Ribera Carlos 2022 research-article