Assessment of fetal position
Knowledge of the fetal head position is particularly critical for forceps deliveries, since it determines the type of forceps delivery being performed (Table 2) and incorrect assessment of position can make forceps placement both less effective and more prone to cause fetal injury. Provider determination of fetal head position is fraught with error with studies showing accuracy ranging from 27% to 80% by digital palpation even by experienced providers.5-7 Ultrasound assessment, on the other hand, has consistently proven more accurate than digital palpation, including in a large, multicenter randomized trial where the accuracy of ultrasound assessment was found to be 98.4%.7 Given the importance of correct determination of fetal position, it is reasonable to consider a bedside ultrasound in patients for whom a forceps delivery is being considered; an excellent expert review was published on the topic by Bellussi, et al and includes an accompanying video demonstrating the technique.8
Anatomy of the forceps
The basic anatomy of the forceps is described in the video, “Anatomy of the forceps”
Types of forceps
The two most commonly used types of forceps for the cephalic presenting fetus are Simpson type and Elliot or Tucker-McLane forceps. The main differences between the two are that the Simpson forceps have shanks that are separated (remember “Simpson shanks separated”) whereas those of the Elliot/Tucker-McLane type are overlapping (remember “Tucker tucked in”). The separated shanks as well as the longer tapering cephalic curve allow for the Simpson type forceps to be used on longer, more molded heads whereas the Elliot or Tucker-McLane types are narrower and might be chosen for the easier pull in a multiparous patient, for example.
The other two commonly used forceps are for special indications. Kielland forceps are used for rotational maneuvers (you “turn a key”) owing to their very slight reverse pelvic curve and sliding lock which allows for correction of asynclitism. The Piper forceps, with their long backward curving shanks and reverse pelvic curve, are designed specifically for stabilization and delivery of the aftercoming head in a breech presentation.
The author reports no potential conflicts of interest with regard to this article.
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