The Western scholarly study of women in Islamic history dates only to the end of the 19th century and the first decades of the 20th. Women are of course mentioned in earlier Orientalist works, as for example The Manners and Customs of the Modern Egyptians by Edward William Lane (1836), and there were several translations and commentaries on the Sīra of Ibn Hishām that made reference to the Prophet's wives. But that hardly counts as research into his wives as such.
The first notable work on women in the Prophet's family was Fatima et les filles de Mahomet by Henri Lammens (1912), which was criticized even in its time for its lack of objectivity. It was a landmark, however.
But it is true we must wait until the 1940s and the work of Nabia Abbott, especially Aisha, the Beloved of Mohammed and her article "Women and the State in Early Islam" (both published in 1942), for the first serious studies focused specifically on women in the lifetime of the Prophet. Abbott's work drew from the whole range of early Arabic sources, including the Sīra, ḥadīth, and all of the major historians of the Classical Arab-Islamic period, and so all studies of women in early Islam rely upon it.
Very early on Orientalists addressed the wives of the Prophet Muhammad as evidence of the Prophet's love for women, with the aim of distorting the image of the Prophet in the mind of the European individual.