Episiotomy and its relationship to various clinical variables that influence its performance

Objective: to understand the episiotomy rate and its relationship with various clinical variables. Method: a descriptive, cross-sectional, analytic study of 12,093 births in a tertiary hospital. Variables: Parity, gestational age, start of labor, use of epidural analgesia, oxytocin usage, position during fetal explusion, weight of neonate, and completion of birth. The analysis was performed with SPSS 19.0. Results: the global percentage of episiotomies was 50%. The clinical variables that presented a significant association were primiparity (RR=2.98), gestational age >41 weeks (RR=1.2), augmented or induced labor (RR=1.33), epidural analgesia use (RR=1,95), oxytocin use (RR=1.58), lithotomy position during fetal expulsion (RR=6.4), and instrumentation (RR=1.84). Furthermore, maternal age ≥35 years (RR=0.85) and neonatal weight <2500 g (RR=0.8) were associated with a lower incidence of episiotomy. Conclusions: episiotomy is dependent on obstetric interventions performed during labor. If we wish to reduce the episiotomy rate, it will be necessary to bear in mind these risk factors when establishing policies for reducing this procedure.


Introduction
Episiotomy is a surgical procedure to widen the inferior part of the vagina, the vulvar ring, and the perineal tissue during the fetal expulsion stage of birth (1) .  The variations in episiotomy rates may be related to the variations in clinical practice related to common obstetric situations such first childbirth, instrumentassisted birth, and epidural use (5-6) .
An analysis of the obstetric variables in the database of the University Clinical Hospital of the Virgin of Arrixaca would be a useful tool for determining factors related to this variability in episiotomy rates.
The objective of the present study is to determine the episiotomy rate and its relationship with particular clinical variables. The obstetric variables collected from the clinical data are shown in Figure 1.

Type of episiotomy
This variable covers three modalities: No episiotomy, when the procedure was not performed, and mediolateral or central, depending on the angle of incision chosen by the professional performing the procedure. Start of labor Spontaneous, induced, and augmented.
Type of birth Vaginal birth (normal vs. with instrumentation -i.e., the use of vacuum, forceps, or spatulas for fetal delivery) and caesarean.

Oxytocin use
The administration of this drug during labor.
Type of analgesia The items recorded are no anesthesia, local, epidural, spinal, and general.
Gestational age For better statistical management, this has been grouped by weeks of gestational as follows: immature (up to 24 weeks), premature (from 24+1 to 36+6), term (from 37 to 41), and post-term (>41 weeks). Neonatal weight Grouped by < 2500 g, between 2500 and 4000 g, and > 4000 g.

Birthing position
During the fetal-expulsion phase, the following positions can be assumed: quadruped, squatting, standing, lateral decubitus, supine decubitus, lithotomy, and seated.

Results
The births, the episiotomy rate was over 90% for all modalities (spatulas, vacuum, and forceps; Table 1).
Regarding the type of analgesia, the data showed a tendency toward episiotomy in births with epidural analgesia compared with those with no analgesia or with local (perineal) analgesia. The statistical test showed that the difference was significant (c 2 =1150.339; p<0.0005), with a moderate effect between the two variables (V=0.307). The RR of episiotomy in women who used epidural analgesia was 1.95.
The analysis of oxytocin administration during birth indicated a statistically significant relationship between episiotomy and oxytocin administration (c 2 =237.527, p<0.0005), although the association was low (V=0.138).
The RR of episiotomy when oxytocin was administered during birth was 1.58 versus not using the drug.  to perform an episiotomy in normal births of neonates with a weight below 2,500 g and in instrumented births of neonates with a weight greater than 4,000 g. In this same manner, the statistical relationship between the variables epidural use, neonatal weight, and episiotomy use was statistically significant for the use of epidural analgesia (c 2 =8.321; p=0.016), although the relational effect was low, V=0.032. The observed tendency was to perform an episiotomy in mothers who used epidural anesthesia and whose neonates weighed more than 4,000 g.

Discussion
Our results show that primiparity is one of the main risk factors associated with episiotomy. This finding coincides with the findings of other authors (5-7) . This variable was considered a confounding factor because in clinical trials with parturient women, it should be controlled. Furthermore, episiotomy in primiparous women presents another implication, as it significantly and independently increases the risk of episiotomy and tears in subsequent births (8) .
Gestational age over 41 weeks constitutes another risk factor associated with episiotomy (RR=1.2). Postterm gestations comprised 12% of the studied births, and of these, 60% had an episiotomy, versus 44.5% of preterm births and 49.6% of term births. This statistic is explained by the tendency to induce labor in post-term births (c 2 =18.085, p>0.005) and by the tendency to complete these births with instrumentation (c 2 =36.315; p=0.02). This data is interesting as it confirms the existence of an "intervention cascade" when there are interventions in normal labor development. This finding was also confirmed by a Cochrane review regarding perineal care that concluded that the use of epidural analgesia increases the likelihood of instrumented birth and episiotomy, thus increasing the risk of perineal trauma (9) .
In the analysis of start of labor in relation to episiotomy, we found that births that began spontaneously had a lower risk of episiotomy than those that were augmented or induced. Our results concur with the findings of other authors, although they associated this relationship with primiparous status (6) . Regarding the method labor induction or augmentation, our results showed a tendency to perform episiotomy in births in which oxytocin is administered versus births in which labor is allowed to evolve normally (54.4% vs 34.4%).
In relation to the type of completion of vaginal birth, instrumentation can be considered a risk factor for episiotomy compared with a normal birth (93% vs 38.7%; RR=1.84). This statistic coincides with the findings of numerous authors (6, [10][11] . The number of episiotomies and instrumented births increases with the complexity of the hospital. As in other specialties, this relationship arises from the referral of complex procedures to centers with greater technological and human resources (12) . The studied hospital delivered 23.4% of births with instrumentation in 2011 and 24.7% in 2012. The role of routine episiotomy in instrumented birth is not well studied and requires more research. It seems that its use is justified by the decrease of perineal tears, especially when forceps are used (13) .
Another variable that influences the use of episiotomy is the type of analgesia used during labor, specifically the use of epidural analgesia. In births in which the woman chooses an epidural as her method of pain relief, episiotomies are more often performed than in those in which no analgesia is used or in which the analgesia is local (58.4% versus 30%). These results coincide with the findings of other authors (6)(7)11,(14)(15)(16) .
Moreover, this tendency is observed regardless of parity and the method of birth completion. Regarding neonatal weight >4000 g, we observed an association between epidural use and episiotomy that increased the risk of Ballesteros-Meseguer C, Carrillo-García C, Meseguer-de-Pedro M, Canteras-Jordana M, Martínez-Roche ME.
Maternal position during the fetal expulsion phase also affects whether an episiotomy will be performed; the lithotomy position was clearly associated with episiotomy compared with other positions (52.2% versus 30%). These results coincide with those of other authors, who also conclude that alternative positions (supine, seated, lateral, standing, squatting, and quadruped) are associated with less frequent use of episiotomy and that it should be left to women to choose the most comfortable position for giving birth (6,11) .
The results showed also protective factors in relation to episiotomy use, such as maternal age and fetal weight.
Maternal age greater than 35 years was associated with a decreased incidence of episiotomy (45.5%) compared with younger ages (54.4%). The reviewed studies suggest that use of episiotomy is not associated with maternal age (10,(19)(20) . This difference may be related to the increased maternal age in our study; the reviewed studies included women up to age 35 years, while our sample comprised a population aged 14 to 53 years, of which 25% were older than 35 years.
In relation to neonatal weight, the results of this study showed a decrease in the episiotomy rate when the neonate weighed <2,500 g (43%) compared with normal weights (53.4%) and weights greater than 4,000 g (57.2%). Other authors did not find this association between neonatal weight and episiotomy (11) . On the contrary, for heavier fetuses (weight >4,000 g), the results showed an increase in episiotomy risk associated with instrumented birth or the use of epidural analgesia (21) .
Our research had some limitations that should be qualified. First, there was possible under-registration of clinical data. Furthermore, a larger sample size from hospitals of various levels would allow a greater generalization of the obtained results.

Conclusion
The episiotomy rate at the studied hospital was higher than the recommendations of WHO, which has found that episiotomy is not an isolated procedure and In addition, there are factors that protect against the performance of episiotomy: fetal weight <2500 g (RR=0.8) and maternal age >35 years (RR=0.8).
Fetal weight >4000 g alone is not a risk factor for episiotomy, but when it was associated with epidural use or instrumented birth, the risk of episiotomy was increased.
Given our results and as a practical implication of the study, if we wish to decrease the episiotomy rate, it will be necessary to bear in mind the factors that influence its practice, establish policies to reduce these procedures, and ensure that they are upon by all health professionals who assist women during the birthing process.