Improving success with forceps delivery
When attempted, forceps are very likely to be successful. A Cochrane review on choice of instruments for assisted vaginal delivery found that failure was 35% less likely with forceps compared to vacuum delivery (9% vs 14% of those attempted).9
It is important, however, to only attempt an operative delivery when it is likely to be successful. A study by Towner, et al found that the likelihood of injury was greatest when sequential interventions were required whether that was an operative attempt then cesarean or sequential operative attempts compared to when a single intervention was successful (i.e., a successful operative delivery or cesarean delivery).10 Improving the likelihood of success in performing a forceps delivery can be achieved by choosing the appropriate candidates, utilizing optimal technique, and avoiding pitfalls that can contribute to failure.
Choosing the candidate
While we will never be able to perfectly choose only those candidates in whom an operative delivery will be successful, certain characteristics can make success less likely.11 Macrosomia has been associated with an increased likelihood of failure in an operative delivery.12-14 This association holds for both vacuum and forceps deliveries; one study found increased odds of failure of 14% for every 100 g increase in estimated fetal weight.13 In addition, macrosomia and operative delivery are independent risk factors for shoulder dystocia. A study performed reviewing 175,000 births in California noted a synergistic effect particularly in diabetic mothers, suggesting additional concerns when considering a forceps delivery in a macrosomic fetus.15
Other factors that have been associated with failure of operative delivery include station at application (low is more likely to fail than outlet), arrest as the indication for operative delivery, prolonged second stage, and occiput posterior presentation.12,14 When possible, occiput posterior presentation can be resolved either by digital rotation or by Scanzoni maneuver (instrumental rotation ideally using Kielland forceps). It is preferable to resolve it since while it is possible to deliver directly OP (as described below in Technique), it is often more difficult, more prone to higher-order lacerations, and was thus discouraged by Dennen in his original forceps textbook.16
We have created a simulation video of a forceps-assisted vaginal delivery for a cephalic presenting fetus in an occiput anterior position delivery and the steps listed in Table 3.
Common pitfalls in technique
Common pitfalls gathered from both performing and teaching learners to perform forceps deliveries are reviewed in Table 4. The most frequent struggles are usually encountered in initial placement – particularly of the second blade – and less commonly during traction. It is important that the cephalic curve (or “palm side” of the blade) is as closely apposed to the fetal scalp as possible, or if the fetal scalp is not visible, then to the maternal introitus. Importantly, as the forceps begins its motion, there can be no movement forward or backward of the handle until the maternal thigh is reached. Doing so starts the blade of the forceps down the sacrum/face (in an OA fetus) rather than along the more hollow space between parietal bone and vagina. A forceps blade on the correct trajectory should require almost no force, and I remind learners of this by encouraging them to hold the handle with only their fingertips.
Related malpractice: Brain injury allegedly caused by forceps
As the forceps lock, if the left blade was placed first, this allows the English lock to come together easily. If, however, the right blade was placed first (as would be the case in a ROA or LOP presentation placing the posterior blade first), then they will appear to come together and be unable to lock. This is easily resolved by moving the left handle so that it falls under the right and the English lock will come together correctly. Last, the correct direction of traction is best achieved by visualizing the presenting part and cardinal movements necessary for delivery. For an OA presentation, this requires direct downward (axis) traction. Only after the occiput clears the symphysis is this then transitioned to outward then upward to minimize perineal injury. For OP presentations, the biparietal diameter is typically much higher than anticipated and Dennen recommends depressing the shanks against the perineum before locking (effectively inching them higher and more anterior on the parietal bone). We have found also that there is typically a much greater need for downward traction initially before then turning outward and upward to take the fetus into flexion for delivery.
The author reports no potential conflicts of interest with regard to this article.
- Martin JA, Hamilton BE, Osterman MJK, Driscoll AK, Drake P. Births: Final Data for 2017. National vital statistics reports : from the Centers for Disease Control and Prevention, National Center for Health Statistics, National Vital Statistics System 2018 Nov;67(8):1-50.
- Caughey AB, Cahill AG, Guise J-M, Rouse DJ, Obstetricians ACo, Gynecologists. Safe prevention of the primary cesarean delivery. Am J Obstet Gynecol. 2014;210(3):179-193.
- Young RL. Obstetrical Forceps: History, Mystery, and Morality. Houston History of Medicine Lectures. [email protected]: John P. McGovern Historical Collections and Research Center; 2011.
- Bulletins—Obstetrics CoP. ACOG Practice Bulletin No. 154: operative vaginal delivery. Obstet Gynecol. 2015;126(5):e56-e65.
- Akmal S, Kametas N, Tsoi E, Hargreaves C, Nicolaides K. Comparison of transvaginal digital examination with intrapartum sonography to determine fetal head position before instrumental delivery. Ultrasound Obstet Gynecol. 2003;21(5):437-440.
- Chou MR, Kreiser D, Taslimi MM, Druzin ML, El-Sayed YY. Vaginal versus ultrasound examination of fetal occiput position during the second stage of labor. Am J Obstet Gynecol. 2004;191(2):521-524.
- Ramphul M, Ooi PV, Burke G, Kennelly MM, Said SA, Montgomery AA, et al. Instrumental delivery and ultrasound : a multicentre randomised controlled trial of ultrasound assessment of the fetal head position versus standard care as an approach to prevent morbidity at instrumental delivery. BJOG. 2014 Jul;121(8):1029-38.
- Bellussi F, Ghi T, Youssef A, Salsi G, Giorgetta F, Parma D, et al. The use of intrapartum ultrasound to diagnose malpositions and cephalic malpresentations. Am J Obstet Gynecol. 2017 Dec;217(6):633-641.
- O’Mahony F, Hofmeyr GJ, Menon V. Choice of instruments for assisted vaginal delivery. Cochrane Database System Rev 2010(11).
- Towner D, Castro MA, Eby-Wilkens E, Gilbert WM. Effect of mode of delivery in nulliparous women on neonatal intracranial injury. N Engl J Med. 1999 Dec 2;341(23):1709-1714.
- Majoko F, Gardener G. Trial of instrumental delivery in theatre versus immediate caesarean section for anticipated difficult assisted births. Cochrane Database System Rev 2012;10:CD005545-CD.
- Gopalani S, Bennett K, Critchlow C. Factors predictive of failed operative vaginal delivery. Am J Obstet Gynecol 2004;191(3):896-902.
- Aiken CE, Aiken AR, Brockelsby JC, Scott JG. Factors influencing the likelihood of instrumental delivery success. Obstet Gynecol. 2014;123(4):796-803.
- Palatnik A, Grobman WA, Hellendag MG, Janetos TM, Gossett DR, Miller ES. Predictors of failed operative vaginal delivery in a contemporary obstetric cohort. Obstet Gynecol. 2016;127(3):501-506.
- Nesbitt TS, Gilbert WM, Herrchen B. Shoulder dystocia and associated risk factors with macrosomic infants born in California. Am J Obstet Gynecol. 1998;179(2):476-480.
- Hale RW. Dennen’s Forceps Deliveries. 4th ed. Washington, DC: The American College of Obstetricians and Gynecologists; 2001.
- Miller ES, Barber EL, McDonald KD, Gossett DR. Association between obstetrician forceps volume and maternal and neonatal outcomes. Obstet Gynecol 2014;123(2 PART 1):248-254.