Controlling for other factors, multivariable analysis resulted in nulliparity conferring a 7.2-fold increased risk for sustaining third- or fourth-degree lacerations (adjusted odds ratio [OR] 7.2, 95% confidence interval [CI] 6.3–8.5) (Table 2). When stratified by parity, Asian or Pacific Islander race was associated with an increased risk for third- or fourth-degree lacerations, more so among multiparous women (adjusted OR 2.2). African American race was not protective (nulliparous OR 0.9, 95% CI 0.7–1.1; multiparous OR 1.3, 95% CI 0.8, 2.2). Among nulliparous women, compared with women younger than age 25, those older than age 25 had an increased risk for third- or fourth-degree lacerations (OR ranging from 1.6 to 1.9 for women older than 25). Increasing maternal BMI was protective in nulliparous, but not multiparous, women. A small protective effect of epidural anesthesia was observed in all parities (nulliparous OR 0.7, 95% CI 0.6–0.8; multiparous OR 0.5, 95% CI 0.4–0.7).
Regardless of parity or type of instrument, women who underwent operative vaginal deliveries experienced three- to five-times the number of third- or fourth-degree lacerations compared with those who underwent spontaneous vaginal deliveries. Episiotomy was performed in 1,575 of the 2,516 (61.6%) women who sustained third- or fourth-degree lacerations, 78% of which were midline. Gestational age itself was not associated with an increased risk for severe perineal laceration, but an increasing birth weight was a strong risk factor in a dose–effect pattern. The presence of a previous uterine scar did not influence the risk of sustaining third- or fourth-degree lacerations, but the risk increased with duration of the second stage.
The fourth column of Table 1 presents characteristics of the 536 women who had cervical lacerations develop. More frequent cervical lacerations occurred in African American and Hispanic women compared with the white and Asian and Pacific Islander populations. Other maternal characteristics included nulliparity, labor induction, oxytocin use, and cerclage. Cervical lacerations were seen more frequently in women with shorter second stages of labor in nulliparous patients.
Multivariable analysis controlling for other factors resulted in nulliparity conferring a small increased risk for sustaining a cervical laceration (adjusted OR 1.3; 95% CI 1.0–1.7). Table 3 illustrates the data for patients with cervical laceration when stratified by parity and adjusted by site. Epidural use in nulliparous women was associated with a small increased risk of cervical laceration (OR 1.5, 95% CI 1.1–2.1) without a relationship to length of labor, gestational age at delivery, or birth weight. For multiparous women, sustaining a cervical laceration was associated with younger age (20 years or younger) oxytocin use (OR 2.5, 95% CI 1.2–5.6), and vacuum vaginal delivery (OR 3.1, 95% CI 1.1–8.7).
Cerclage was highly associated with an increased risk of cervical laceration, with a 3.7-fold increased risk in nulliparous women (adjusted OR 3.7, 95% CI 1.1–12.8) and a 12.7-fold increased risk in multiparous women (adjusted OR 12.7, 95% CI 5.7–28.2; Table 3).
In current obstetric practice with less episiotomy and forceps use combined with an increased cesarean delivery rate, previously reported risk factors for third- and fourth-degree lacerations continue to be significantly associated with risk of laceration. These include nulliparity,11,15 increasing gestational age,16 increasing birth weight,4,7,15 operative vaginal delivery,4,7,15,17 increasing length of the second stage of labor,7,11,18 and episiotomy.4,14,17,19 Ethnic variability also has been reported with higher risks among women of non-African American ethnicity,20 particularly among Asian women.5 In addition, cervical lacerations represent a complication that is not well-detailed in the literature. From our sizeable patient population, we determined a major risk factor for cervical lacerations to be cervical cerclage. Other risk factors included epidural use in nulliparous women and, among multiparous patients, age 20 years or younger, oxytocin use, and vacuum vaginal delivery were identified.
A decreased association of third- or fourth-degree lacerations was identified among patients with epidural, which is something not previously reported. Epidural use is associated with a longer second stage of labor and higher rates of operative vaginal delivery, both of which increase the risk of perineal lacerations.21,22 In a multivariable model controlling for these variables, our reported lower risk of third- or fourth-degree lacerations associated with epidural use perhaps might also be explained by having more controlled crowning and delivery of the head with resulting fewer lacerations.
We found third- or fourth-degree lacerations to be highly associated with episiotomy use: 2.4-fold in nulliparous women and 4.4-fold in multiparous women. More than 62% of women with third- or fourth-degree lacerations had episiotomies performed (1,575 of 2,516 patients); this is concerning given clear published recommendations for restrictive episiotomy use.6 It can be postulated that in a scenario involving a patient with key clinical characteristics (eg, nulliparity, increased gestational age, increased fetal weight, and increased duration of the second stage of labor), an obstetrician would be inclined to undertake clinical actions to facilitate a vaginal delivery, proceeding with episiotomy and use of vacuum or forceps. Our data provide more support and strongly confirm the practice of restrictive episiotomy in modern obstetrics.
The major strength of this study is the large amount of data pertaining to 536 women with cervical lacerations. Melamed et al10 described 131 cases of women with cervical lacerations, identifying risk factors of cervical cerclage during pregnancy, precipitous labor (delivery 3 hours or less after the onset of active labor), episiotomy, and vacuum extraction.10 Another 2007 study retrospectively identified 32 patients from a cohort of 16,391 deliveries and described significant associations with labor induction and cervical cerclage during pregnancy similar to our findings. These authors9 did not find an association with operative vaginal delivery, contrary to Melamed's report,10 and our data demonstrating an association with vacuum delivery in multiparous patients, perhaps because of the small numbers in their study.9 In our study, oxytocin use in multiparous women conferred a 2.5-fold risk of cervical laceration and the major risk factor for cervical lacerations was found to be cerclage regardless of parity (3.7-fold risk in nulliparous and 12.7-fold increased risk in multiparous women).
Our study provides insight into current obstetric practice in a large diverse population. However, the results and conclusions are limited by a phenomenon known as informative censoring attributable to the high rate of cesarean delivery, which occurred in 43.8% of women attempting vaginal delivery from the entire cohort.14 Only women who had a vaginal delivery were at risk for laceration, which may to some degree explain the association between the decreased risk of third- or fourth-degree lacerations with higher maternal BMI that has not been observed in other studies.24,25 It is known that women with an increased BMI have a higher risk of cesarean delivery.23–25 Perhaps in our population, the women with a higher BMI who achieved successful vaginal deliveries are different than women with a higher BMI who had cesarean delivery (eg, having smaller fetuses, which would be associated with a decreased risk for severe perineal laceration). The lower laceration risk we describe with higher BMI also could be explained by less willingness for obstetricians to attempt operative vaginal deliveries in patients at high risk, such as obese women, because of uncertainty about fetal weight and risks of shoulder dystocia. Another possibility is that in this select group of women, their extra soft tissue might protect against development of these lacerations. Thus, the risk factors associated with laceration in the present study only apply to a population of women in whom the cesarean rate is very high, which is in the context of current U.S. obstetric practice.
Limitations of our study include the fact that some areas of interest could not be explored to the fullest because of its retrospective nature and inherent reliance on data that were entered into patients' electronic medical records, such as unspecified or unknown method of induction, type of operative vaginal delivery, or identification of multiparous women with previous severe obstetric lacerations. Additionally, our findings are not fully generalizable to the U.S. population because of the need to eliminate a number of sites that did not record information on perineal laceration or cerclage use, which was an important risk factor for cervical laceration. However, a major strength of this study is the direct clinical information derived from our large, diverse, and contemporary population, reflecting current obstetric practice, as well as the considerable amount of data pertaining to 536 women with cervical lacerations.
In summary, third- or fourth-degree lacerations and cervical lacerations represent significant morbidities associated with vaginal deliveries. In an era of high rates of cesarean delivery, we found the risk factors for third- or fourth-degree lacerations to be unchanged. Episiotomy continues to be a major potentially modifiable risk factor and efforts should be made to continue to limit this procedure to only when medically necessary. Cervical lacerations are associated with cerclage placement and some instances of oxytocin use, which may not be fully modifiable; however, full assessment of risks and benefits should be considered before their implementation. Many clinical risk factors are predetermined and use of episiotomy, oxytocin use, and cerclage represent three potentially modifiable practices.
1. Fenner DE, Genberg B, Brahma P, Marek L, DeLancey JO. Fecal and urinary incontinence after vaginal delivery with anal sphincter disruption in an obstetrics unit in the United States. Am J Obstet Gynecol 2003;189:1543–9; discussion 1549–50.
2. Kammerer-Doak D, Rogers RG. Female sexual function and dysfunction. Obstet Gynaecol Clin N Am 2008;35:169–83.
3. American College of Obstetricians and Gynecologists. Cervical Insufficiency. Practice Bulletin 48. Washington, DC: American College of Obstetricians and Gynecologists; 2003.
4. Lowder JL, Burrows LJ, Krohn MA, Weber AM. Risk factors for primary and subsequent anal sphincter lacerations: a comparison of cohorts by parity and prior mode of delivery. Am J Obstet Gynecol 2007;196:344.e1–5.
5. Hopkins LM, Caughey AB, Glidden DV, Laros RK Jr. Racial/ethnic differences in perineal, vaginal and cervical lacerations. Am J Obstet Gynecol 2005;193:455–9.
6. Carroli G, Mignini L. Episiotomy for vaginal birth. The Cochrane Database of Systemic Reviews 2009, Issue 1. Art. No.: CD000081.
7. Mikolajczyk RT, Zhang J, Troendle J, Chan L. Risk factors for birth canal lacerations in primiparous women. Am J Perinatol 2008;25:259–64.
8. Frankman EA, Wang L, Bunker CH, Lowder JL. Episiotomy in the United States: has anything changed? Am J Obstet Gynecol 2009;200:573.e1–7.
9. Parikh R, Brotzman S, Anasti JN. Cervical lacerations: some surprising facts. Am J Obstet Gynecol 2007;196:e17–8.
10. Melamed N, Ben-Haroush A, Chen R, Kaplan B, Yogev Y. Intrapartum cervical lacerations: characteristics, risk factors, and effects on subsequent pregnancies. Am J Obstet Gynecol 2009;200:388.e1–4.
11. Rouse DJ, Weiner SJ, Bloom SL, Varner MW, Spong CT, Ramin SM, et al. Second-stage labor duration in nulliparous women: relationship to maternal and perinatal outcomes. Am J Obstet Gynecol 2009;201:357.e1–7.
12. American College of Obstetrics and Gynecology. ACOG Practice Bulletin Number 49, December 2003. Dystocia and augmentation of labor. Obstet Gynecol 2003;102:1445–54.
13. Zhang J, Troendle JF, Yancey MK. Reassessing the labor curve in nulliparous women. Am J Obstet Gynecol 2002;198:824–8.
14. Zhang J, Troendle J, Reddy UM, Laughon SK, Branch DW, Burkman R, et al. Contemporary cesarean delivery practice in the United States. Am J Obstet Gynecol 2010;203:326.e1–10.
15. Richter HE, Brumfield CG, Cliver SP, Burgio KL, Neely CL, Varner RE. Risk factors associated with anal sphincter tear: a comparison of primiparous patients, vaginal births after cesarean deliveries, and patients with previous vaginal delivery. Am J Obstet Gynecol 2002;187:1194–8.
16. Caughey AB, Stotland NE, Washington EW, Escobar GJ. Maternal and obstetric complications of pregnancy are associated with increasing gestational age at term. Am J Obstet Gynecol 2007;196:155.e1–6.
17. Kudish B, Blackwell S, Mcneeley G, Bujold E, Kruger M, Hendrix SL, et al. Operative vaginal delivery and midline episiotomy: A bad combination for the perineum. Obstet Gynecol 2006;195:749–54.
18. Cheng YW, Hopkins LM, Caughey AB. How long is too long: Does a prolonged second stage of labor in nulliparous women affect maternal and neonatal outcomes? Am J Obstet Gynecol 2004;191:9833–8.
19. Rodriguez A, Arenas EA, Osorio AL, Mendez O, Zuleta JJ. Selective vs routine midline episiotomy for the prevention of third- or fourth- degree lacerations in nulliparous women. Am J Obstet Gynecol 2008;198:285.e1–4.
20. Howard D, Davies PS, DeLancey JO, Small Y. Differences in perineal lacerations in black and white primiparas. Obstet Gynecol 2000;96:622–4.
21. Anim-Somuah M, Smyth RMD, Howell CJ. Epidural versus non-epidural or no analgesia in labour. The Cochrane Database of Systemic Reviews 2005, Issue 4. Art. No.:CD000331.
22. Liu EH, Sia AT. Rates of caesarean section and instrumental vaginal delivery in nulliparous women after low concentration epidural infusions or opioid analgesia: systematic review. BMJ 2004;328:1410–5.
23. Minaglia SM, Kimata C, Soules KA, Pappas T, Oyama IA. Defining an at-risk population for obstetric anal sphincter laceration. Am J Obstet Gynecol 2009;201:526.e1–6.
24. Kominiarek MA, VanVeldhuisen P, Hibbard J, Landy H, Haberman S, Learman L, et al. The maternal body mass index: a strong association with delivery route. Am J Obstet Gynecol 2010;203:264.e1–7.
© 2011 The American College of Obstetricians and Gynecologists
25. Heslehurst N, Simpson H, Ellis LJ, Rankin J, Wilkinson J, Lang R, et al. The impact of maternal BMI status on pregnancy outcomes with immediate short-term obstetric resource implications: a meta-analysis. Obes Rev 2008;9:635–83.