Background: Maternity care has focused on lowering maternal and neonatal morbidity, though women's beliefs and expectations of care have been set aside. Women face childbirth with preconceived expectations, some of which could be expressed on their birth plan. The latter could beinfluenced by health professionals through prenatal education classes, though this has not been measured before. Antenatal classes have been argued against,since no resulting improvement in childbirth experience has been demonstrated, though some advantages may be seen: they favour communication and give time for expressing maternal expectations and beliefs. The present study evaluates the influence of prenatal educational classes led by midwives upon women birth preferences. Methods: A multicentre, observational, prospective study was carried out, measuring variables in pregnant women attending prenatal educational classes in different health centres within the health districts in Valencia (Spain) over the period January-October 2012. Birth plan preferences were compared prior to and upon completion of the classes. Results: A total of 212 eligible pregnant women (78.3% nulliparous) with an average age of 31.39±4.0 years consented to participate in the study. There were significant differences in birth plan preferences prior to and upon completion of the prenatal classes. Three items showed an increase between the initial session and the end of the intervention: the ability to push spontaneously, episiotomy avoidance, and early breastfeeding. An adjusted general linear model was used to compare pre-post results in relation to sociodemographic and obstetric variables. Discussion: The changes in birth plans could suggest that prenatal educational classes exert an influence upon maternal birth preferences.