Since the 1970s, international activist movements have denounced a medical and techno-centric approach to birth. In response to this "techno-bio-medicalization" of birth, the concept of humanized childbirth emerged in the 1990s in Latin America and then became global. This article proposes to analyse the failure of a Japanese project of humanized childbirth in a maternity hospital in Benin. On the basis of participant observations and interviews, we show that the proposal of Japanese development actors came up against a strong incorporation of obstetrical science by the health workers and more particularly by the Beninese midwives. More specifically, by forbidding the presence of an attendant near the woman giving birth and by refusing to accept a position other than the gynaecological one, the midwives reproduce the dominant model of biomedicalization of childbirth to the detriment of women's comfort and psychological and social well-being.