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The Association of Maternal Age and Symptomatic Uterine Rupture During a Trial of Labor After Prior Cesarean Delivery

From the Departments of Obstetrics and Gynecology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, University of Connecticut Health Center, Farmington, Connecticut, University of Nebraska Medical Center, University of Nebraska, Omaha, Nebraska, and University of California, San Francisco, San Francisco, California.

Address reprint requests to: Thomas D. Shipp, MD, Brigham and Women’s Hospital, Department of Obstetrics and Gynecology, CWN 3, 75 Francis Street, Boston, MA 02115; E-mail: tshipp{at}partners.org.

	ABSTRACT

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OBJECTIVE: To estimate whether maternal age is associated with a symptomatic uterine rupture during a trial of labor after prior cesarean delivery.

METHODS: We retrospectively reviewed the medical records of all patients undergoing a trial of labor after prior cesarean delivery over a 12-year period. We analyzed the labors of women with one prior cesarean and no prior vaginal deliveries. The uterine rupture rate was determined with respect to maternal age. Multiple logistic regression was used to control for potential confounding variables.

RESULTS: Overall, 32 (1.1%) uterine ruptures occurred among 3015 women. For women younger than 30 years, the risk of uterine rupture was 0.5%, and for those women aged at least 30 years, the risk of uterine rupture was 1.4% (P = .02). Controlling for birth weight, induction, augmentation, and interdelivery interval, the odds ratio for symptomatic uterine rupture for women aged at least 30 years compared with those less than 30 years was 3.2 (95% confidence interval 1.2, 8.4).

CONCLUSION: Women aged 30 years or older have a greater risk of uterine rupture as compared with women younger than 30 years.

Women are having babies later in life. The birth rate for women in their 30’s is the highest it has been in three decades, and for women in their 40’s, the rate is the highest it has been in two decades.¹ In Massachusetts, more than half of the women giving birth are now older than 30 years.² It has been known for some time that women who are 35 years or older are at increased risk for cesarean delivery.³ This rate appears to increase incrementally with maternal age.⁴ Older women are at increased risk for cesarean delivery, and they now represent a higher proportion of deliveries; therefore, the potential risks for such women during labor should be clearly determined.

Trial of labor is a common practice for delivery of the parturient with a prior cesarean delivery. The most worrisome risk during a trial of labor after cesarean delivery is a symptomatic uterine rupture because it may result in significant maternal and fetal morbidity. Our objective was to assess whether maternal age is independently associated with a symptomatic uterine rupture during a trial of labor after prior cesarean delivery.

	MATERIALS AND METHODS

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Medical records for all patients entering Brigham and Women’s Hospital for a trial of labor after prior cesarean delivery over a 12-year period (July 1984–June 1996) were reviewed. Specific abstracted data have been previously reported.^5,6 The current analysis was limited to those women with singleton pregnancies, only one prior cesarean delivery, and no prior vaginal deliveries.

We defined uterine rupture as complete disruption of the prior cesarean scar with one or more of the following associated symptomatic factors: hemorrhage, need for hysterectomy, damage to the bladder, extrusion from the uterus of any portion of the fetal-placental unit, or indicated cesarean delivery for nonreassuring fetal testing or suspected uterine rupture.⁵

The rate of uterine rupture and clinical characteristics were determined with respect to maternal age. Statistical comparisons for categoric variables were performed using ² or Fisher exact test, as appropriate, and Student t test was used to compare continuous variables. Multiple logistic regression was used to assess the risk for uterine rupture with respect to maternal age while controlling for potential confounding variables. The study was approved by the Institutional Review Board at Brigham and Women’s Hospital.

	RESULTS

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There were 3015 women undergoing a trial of labor who had only one prior cesarean delivery with no prior vaginal deliveries. Within this group, there were 32 uterine ruptures (1.1%). The uterine rupture rate by maternal age is shown in Figure 1. The rate of symptomatic uterine rupture for those younger than 30 years was lowest. The rate of symptomatic uterine rupture was not significantly different between the three higher age groups (P = .6). As seen in Table 1, for women younger than 30 years, the rate of rupture was 0.5%, and for those 30 years or older, the rate was 1.4% (P = .02). Those older parturients were no more likely to have macrosomic neonates or to have labor augmented, but were more likely to be induced compared with women younger than 30 years, as seen in Table 1. A small number of women received prostaglandin gel for induction in each group. The gestational age at delivery and length of labor was also similar between those less than 30 years, and those 30 years or older. There was a difference between the two groups with regard to prior uterine scar type. Those women younger than 30 years were more likely to have had prior low vertical incisions, and those 30 years or older were more likely to have had prior low transverse incisions as seen in Table 1.

View larger version (23K): [in this window] [in a new window]   Figure 1. Rate of symptomatic uterine rupture according to increasing maternal age (years). P = .6 comparing rates for those women 30–34, 35–39, and older than 39 years. P = .02 for comparing those women younger than 30 with those 30 years or older. Shipp. Maternal Age and Uterine Rupture. Obstet Gynecol 2002.

	DISCUSSION

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The association of uterine rupture and age has previously been reported.⁸ However, although Gregory et al reported an increase in uterine rupture with maternal age, they were unable to control for the potential confounding factors of parity or number of prior cesarean deliveries.⁸ We addressed these issues by including only women having one prior cesarean delivery and no prior vaginal deliveries, and we have shown that maternal age has a statistically significant independent association with symptomatic uterine rupture.

Uterine incisions after cesarean delivery appear to heal by scar formation⁹ as opposed to myometrial regeneration as has been previously suggested. Increasing age is a critical factor in the risk for abdominal wound dehiscence.¹⁰ Although it is possible that factors related to healing could contribute to the increase in uterine rupture, the specific factors responsible for the higher rate of uterine rupture with increasing maternal age remain to be elucidated.

Potential limitations of the study should be discussed. In spite of the large number of trials of labor in this study, we had a limited number of women who were over 39 years. Although there was no statistically significant difference in the rate of uterine rupture comparing the three older age groups (ie, women 30–34 years, 35–39 years, and over 39 years), women over 39 years did have a somewhat higher rate of symptomatic uterine rupture. Because the number of women in that group was relatively small and included only three ruptures, it is not possible to determine with certainty from our data whether women over 39 years are at somewhat increased risk of uterine rupture. A prospective evaluation of the risk of uterine rupture during a trial of labor after prior cesarean delivery may be helpful to determine the significance of maternal age and the risk of symptomatic uterine rupture, especially for those over 39 years. Also, as this is a retrospective study, we are unable to control for other unidentified confounding factors.

The change in risk of uterine rupture with maternal age may be important for women who are deciding whether or not to attempt a trial of labor. Although symptomatic uterine rupture is more frequent among women who are 30 years or older as compared with those younger than 30 years, the risk is still low. Other factors that are associated with an increased risk for symptomatic uterine rupture have a magnitude of risk greater than that which we have observed in this study. For example, women with multiple prior cesarean deliveries have a risk of symptomatic uterine rupture approximately 4.8 times that of women with only one prior cesarean delivery,¹¹ and women with their labor induced after prior cesarean delivery have a risk of uterine rupture 4.6 times that of women in spontaneous labor.⁷ Data related to maternal age and other risk factors may be helpful for determining the risk for uterine rupture and should be incorporated into scoring systems for predicting the risk of uterine rupture for women undergoing a trial of labor after prior cesarean delivery.

	Footnotes

 
PII S0029-7844(01)01792-6

Received September 24, 2001. Received in revised form November 28, 2001. Accepted December 11, 2001.

	REFERENCES

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1. Curtin SC, Martin JA. Births: Preliminary data for 1999. Centers for Disease Control and Prevention. Nat Vital Stat Reports 2000;48:1–6.

2. Massachusetts births 1999. Massachusetts Department of Public Health, Bureau of Health Statistics, Research and Evaluation, Bureau of Family and Community Health, January 2001.

3. Lieberman E. Predictors of cesarean delivery. Curr Probl Obstet Gynecol Fertil 1997;20:93–132.

4. Curtin SC. Rates of cesarean birth and vaginal birth after previous cesarean, 1991–1995. Centers for Disease Control and Prevention. Monthly Vital Stat Reports 1997; 45(Suppl. 3):1–12.

5. Shipp TD, Zelop CM, Repke JT, Cohen A, Caughey AB, Lieberman E. Intrapartum uterine rupture and dehiscence in patients with prior lower uterine segment vertical and transverse incisions. Obstet Gynecol 1999;94:735–40.[Abstract/Free Full Text]

6. Caughey AB, Shipp TD, Repke JT, Zelop C, Cohen A, Lieberman E. Trial of labor after cesarean delivery: The effect of previous vaginal delivery. Am J Obstet Gynecol 1998;179:938–41.[Medline]

7. Zelop CM, Shipp TD, Repke JT, Cohen A, Caughey AB, Lieberman E. Uterine rupture during induced or augmented labor in gravid women with one prior cesarean delivery. Am J Obstet Gynecol 1999;181:882–6.[Medline]

8. Gregory KD, Korst LM, Cane P, Platt LD, Kahn K. Vaginal birth after cesarean and uterine rupture rates in California. Obstet Gynecol 1999;94:985–9.[Abstract/Free Full Text]

9. Wojdecki J, Grynsztajn A. Scar formation in the uterus after cesarean section. Am J Obstet Gynecol 1970;107: 322–4.[Medline]

10. Riou J-PA, Cohen JR, Johnson H Jr. Factors influencing wound dehiscence. Am J Surg 1992;163:324–30.[Medline]

11. Caughey AB, Shipp TD, Repke JT, Zelop CM, Cohen A, Lieberman E. Rate of uterine rupture during a trial of labor in women with one or two prior cesarean deliveries. Am J Obstet Gynecol 1999;181:872–6.[Medline]

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