Imagine, for a moment, what it must have been like in the birthing chambers of the 17th and 18th centuries. While most births went according to plan, there could be difficult cases–the baby might be turned wrong, the mother’s pelvis might be too narrow: the complications could be endless. Where would the midwife turn? There were no lying hospitals at this time, and no emergency squad. At best, a midwife might turn to the surgeon–not to save the infant, generally, but to save the mother (often at the expense of the child). As a result, no one wanted to summon the surgeon–or his “instruments.” It meant things were not going well. But in the latter part of the 17th century, all of this was about to change.
In 1569, a family of Huguenots (members of the Protestant Reformed Church of France) fled religious persecution and settled in England. Their surname name was Chamberlen, and this enterprising family forever changed the world of obstetrics. Described by Bryan Hibbard as bold, undaunted, and even unethical and “rogue”-like,  the Chamberlens made as many enemies as friends, particularly in the practice of medicine. But they were hard-working, too, innovative and creative. Sometime in the late 16th century, Peter the elder invented an unusual device for the purpose of delivering children alive even during difficult labors. The hinged, spoon-like instrument would later be called forceps–but for the next several decades, they were known largely as “the secret.”
Stories of how the Chamberlen’s did business are, understandably, given to embellishment–but after all, they had a secret to protect. They carried something with them that could mean life to both mother and child, and they might have done a bit of show-boating to distract the public (while marketing their services). They drove to births in closed or curtained carriages, and it is rumored that they carried “the secret” in an enormous, gold-covered box that required at least two people to carry it.  It has also been recorded that patients were blind-folded and that everyone else was required to leave the room during the delivery. As Hugh Chamberlen (grandson of Peter the elder) explained in 1673:
My father, brothers and myself (tho’ none else in Europe as I know) have by God’s blessing and our own industry, attained to and long practiced a way to deliver women [...] without any prejudice to them or their infants. 
The mystery of the device naturally would have has its own appeal, but only if it was also practical and successful. Fear of complication might encourage a woman to “bespeak” the Chamberlens, that is, to ask in advance for their services (instead of calling for them–as for the surgeon–only as a last resort.) An example of this can be seen with a later practitioner, William Giffard. According to Adrian Wilson, he was the first non-Chamberlen to use the device in England, and “The more it was known [the surgeon] could deliver a living child, the less women would fear him; the less they feared him, the earlier they would call him; the earlier they called him, the more often he could deliver the child alive; and the more other this was so, the further it would be realized that he could achieve this”  In other words, the more successful the Chamberlen forceps were, the more famous and in demand they would become.
Eventually, the secret was out–this we can tell from the sudden explosion of modified instruments in the hands of private physicians. How did this happen? We still cannot be sure, though there are many odd and unusual tales about it, often with no supporting evidence. For instance, in Ogilvy’s “Confessions of an Advertising Man,” he claims that an enterprising medical student climbed up and peeked through the window of the Chamberlen surgery (very unlikely, especially since the Chamberlens traveled to their patients rather than working in a surgery, as was common in later centuries). One widely held and justifiable belief is that Hugh Chamberlen, who relocated to Amsterdam, sold the secret (or part of it) for much needed funds. In any case, the first written account of the secret’s publication abroad comes from the 1740s and is attributed to Van Roonhuysian, a surgeon in Amsterdam.  By the mid-eighteenth century, they were widespread, if not universally accepted. True popularization and innovation came with the latter-century work of William Smellie and Andre Levret.
No longer the ‘mythic’ means of delivering during difficult births, the instruments still had a kind of mystery about them. Certainly, the women upon whom they were used rarely saw them–women were delivered beneath a sheet for propriety’s sake and could not see what their doctors or midwives were up to. (One can imagine is was rather difficult for the doctors themselves). The wooden forceps developed (and later abandoned) by Smellie were designed not to ‘clank’ and therefore alert the laboring woman to their presence. Smellie also developed forceps with different curves and handles–and Levret developed new forceps for use in France. Later in the 18th century, David Orme would develop shorter, straighter forceps that could be used from any direction (rather than only with the pelvic curve). But there is yet another important development in the use of these instruments–in making them standard for delivery, these male practitioners further edged out the last of the female midwives in practice during the 18th century.
Female midwives were not allowed to use instruments. Instrumentation had been one of the ways in which male surgeons protected their interests, for only a surgeon could wield instruments, and only those wielding instruments could be considered surgeons. Medical technology was the male calling card, so to speak, his identity in practice. Use of instruments meant that difficult births were increasingly seen as the purview of surgeons, not of midwives, and it is a very short distance between this early win and the practice of engaging surgeon-midwives as the primary practitioner rather than a grim last resort.
Thus, the last trick of these “mystery instruments” is that they were (pardon the pun) instrumental to increasing the reputation of man-midwives.
 Hibbard, Bryan. The Obstetrician’s Armamentarium. (San Anselmo: Norman Publishing, 2000): 9
 Ibid., 13
 Ibid., 14
 Wilson, Adrian. The Making of Man-Midwifery. (Cambridge: Harvard University Press, 1995), 97.
 Hibbard, 19