William Smellie (1792) Wooden<unk>  c.1800, Hunterian Museum, Glasgow James Young Simpson's Caesarian<unk> , Hunterian Museum, Glasgow Obstetric<unk>  consist of two branches (blades) that are positioned around the head of the fetus. These branches are defined as left and right depending on which side of the mother's pelvis they will be applied. The branches usually, but not always, cross at a midpoint, which is called the articulation. Most<unk>  have a locking mechanism at the articulation, but a few have a sliding mechanism instead that allows the two branches to slide along each other.<unk>  with a fixed lock mechanism are used for deliveries where little or no rotation is required, as when the fetal head is in line with the mother's pelvis.<unk>  with a sliding lock mechanism are used for deliveries requiring more rotation. The blade of each<unk>  branch is the curved portion that is used to grasp the fetal head. The<unk>  should surround the fetal head firmly, but not tightly. The blade characteristically has two curves, the cephalic and the pelvic curves. The cephalic curve is shaped to conform to the fetal head. The cephalic curve can be rounded or rather elongated depending on the shape of the fetal head. The pelvic curve is shaped to conform to the birth canal and helps direct the force of the traction under the pubic bone.<unk>  used for rotation of the fetal head should have almost no pelvic curve. The handles are connected to the blades by shanks of variable lengths.<unk>  with longer shanks are used if rotation is being considered. Anglo-American types All American<unk>  are derived from French<unk>  (long<unk>  or English<unk>  (short<unk> . Short<unk>  are applied on the fetal head already descended significantly in the maternal pelvis (i.e., proximal to the vagina). Long<unk>  are able to reach a fetal head still in the middle or even in the upper part of the maternal pelvis. At present practice, it is uncommon to use<unk>  to access a fetal head in the upper pelvis. So, short<unk>  are preferred in the UK and USA. Long<unk>  are still in use elsewhere. Simpson<unk>  (1848) are the most commonly used among the types of<unk>  and has an elongated cephalic curve. These are used when there is substantial molding, that is, temporary elongation of the fetal head as it moves through the birth canal. Elliot<unk>  (1860) are similar to Simpson<unk>  but with an adjustable pin in the end of the handles which can be drawn out as a means of regulating the lateral pressure on the handles when the instrument is positioned for use. They are used most often with women who have had at least one previous vaginal delivery because the muscles and ligaments of the birth canal provide less resistance during second and subsequent deliveries. In these cases the fetal head may thus remain rounder. Kielland<unk>  (1915, Norwegian) are distinguished by having no angle between the shanks and the blades and a sliding lock. The pelvic curve of the blades is identical to all other<unk> . The common misperception that there is no pelvic curve has become so entrenched in the<unk> iterature that it may never be able to be overcome, but it can be proved by holding a blade of Kielland's against any other<unk>  of one's choice. Kielland<unk>  are probably the most common<unk>  used for rotation. The sliding mechanism at the articulation can be helpful in asynclitic births (when the fetal head is tilted to the side) since it is no longer in line with the birth canal. Because the handles, shanks, and blades are all in the same plane the<unk>  can be applied in any position to affect rotation. Because the shanks and handles are not angled, the<unk>  cannot be applied to a high station as readily as those with the angle since the shanks impinge on the perineum. Wrigley's<unk> , named after Arthur Joseph Wrigley, are used in low or outlet deliveries (see explanations below), when the maximum diameter is about above the vulva. Wrigley's<unk>  were designed for use by general practitioner obstetricians, having the safety feature of an inability to reach high into the pelvis. Obstetricians now use these<unk>  most commonly in cesarean section delivery where manual traction is proving difficult. The short length results in a lower chance of uterine rupture. Piper's<unk>  has a perineal curve to allow application to the after-coming head in breech delivery.
Obstetrical forceps
Forceps
Dermacentor
Caesarean section
Natural childbirth
Condom machine
Labor induction
Debakey forceps