The book by Alice Dreger reviewed by Dr Kessel in the December 2004 JRSM1 is a wonderful portrayal of the painful curiosity, acclaim, and social stigma variously associated with conjoined twins, as well as the role of the heroic operations developed for their separation. Yet no single volume can include all cases of conjoined twins. Indeed, one set is regrettably underappreciated by modern sciences—the Blazek sisters of Bohemia (1878–1922). They represent an extreme manifestation of the terminal monogenital pygopagus subset of conjoined twins, with fusion of sacrum/pelves and a combined (septated) vagina. Indeed, the Blazek sisters stand out as the only known conjoined twins who themselves conceived and delivered a baby (a normal healthy male). Truly unique in the archive of medicine, one sister continued to menstruate through a shared vagina until the 32nd week of her conjoined twin's pregnancy. While the better known 'Siamese twins' Chang and Eng Bunker left historians a vast cultural legacy in all manner of poetry, portraiture and song, traces of the Blazek sisters (who likwise toured and exhibited extensively) have now all but vanished. Why has their story been forgotten? Although the Blazek's weaker marketing strategy might be to blame, the paucity of formal reports describing these twins in the medical literature certainly contributes to their present obscurity.2,3 Surprisingly, many 'comprehensive' obstetrics textbooks still miss this highly unusual reproductive accomplishment even in their footnotes. Nevertheless, in physiology it is from observations of the extreme where most is learned about what is possible among the ordinary. As the Blazek story slips into oblivion, our field risks losing another reminder that, even in the era before complex surgery, conjoined twins were not always consigned to an incomplete reproductive career.