Labor stimulation with oxytocin: effects on obstetrical and neonatal outcomes

Abstract Objective: to evaluate the effects of labor stimulation with oxytocin on maternal and neonatal outcomes. Method: descriptive and analytical study with 338 women who gave birth at a tertiary hospital. Obstetric and neonatal variables were measured and compared in women submitted and non-submitted to stimulation with oxytocin. Statistics were performed using Chi-square test, Fisher exact test, Student t-test; and crude Odds Ratio with 95% confidence interval were calculated. A p < 0.05 was considered statistically significant. Results: stimulation with oxytocin increases the rates of cesarean sections, epidural anesthesia and intrapartum maternal fever in primiparous and multiparous women. It has also been associated with low pH values of umbilical cord blood and with a shorter duration of the first stage of labor in primiparous women. However, it did not affect the rates of 3rd and 4th degree perineal lacerations, episiotomies, advanced neonatal resuscitation, 5-minute Apgar scores and meconium. Conclusion: stimulation with oxytocin should not be used systematically, but only in specific cases. These findings provide further evidence to health professionals and midwives on the use of oxytocin during labor. Under normal conditions, women should be informed of the possible effects of labor stimulation with oxytocin.

induction and use of regular care interventions, as well as unnecessary restrictions. However, a meta-analysis with 10 randomized controlled trials (10) concluded that high doses of oxytocin for labor stimulation was associated with reduction in the rates of cesarean sections and shorter duration of labor, without increasing the maternal and perinatal adverse outcomes.
The World Health Organization stressed the need to revise the biomedical care model during pregnancy and childbirth, which is characterized by a high interventionism and excessive medicalization in developed countries. In its recommendations on the care during normal birth, certain practices and interventions were considered inadequate, such as amniotomy or early artificial rupture of the amniotic sac and regular use of oxytocin, among other (11) .
In Spain, in the Normal Birth Care Strategy, the Ministry of Health has recommended the limited use of oxytocin (12) .
Labor stimulation with oxytocin and early amniotomy used to be carried out regularly in the hospital where this study was conducted, a tertiary hospital in the South of Spain; however, their use have been currently reduced.
The aim of this study was to evaluate the effects of labor stimulation with oxytocin on the maternal and neonatal outcomes. The specific objectives were: to compare the rates of cesarean sections, 5-minute Apgar scores, arterial pH values of umbilical cord blood and type of neonatal resuscitation required, between women submitted and non-submitted to stimulation with oxytocin.

Methods
This is a descriptive and analytical study carried out in a tertiary hospital in the South of Spain, with 338 women who gave birth from September 2011 to September 2013. This is a highly specialized hospital of regional and national reference, which primarily serves women from the city and downtown area of the province. About 4,000 women are assisted a year for childbirth in this hospital.
The study population was comprised of all women, primiparous and multiparous, with spontaneous labor onset assisted during this period.
Inclusion criteria were: delivery at full term, lowrisk pregnancy and childbirth, spontaneous onset of labor, single delivery with cephalic presentation. Women with induced labor and those who were not in labor due to elective or emergency cesarean section were excluded.
Two groups were established, women whose labor was stimulated with oxytocin and women who did not receive oxytocin and whose delivery progressed spontaneously. Different obstetrical and neonatal variables were measured and compared between the two groups.
Stimulation with oxytocin is defined as the administration of oxytocin to improve and/or increase the frequency and intensity of contractions in women whose delivery begins spontaneously. Oxytocin perfusion For data analysis, the statistical Chi-square and Fisher exact tests were used for qualitative variables, and Student's t-test was used for quantitative variables.
The first are expressed as frequencies and percentages, whereas the latter are expressed as mean and standard

deviation. Crude Odds Ratios with 95% Confidence
Interval were also calculated for each variable. P<0.05 was considered statistically significant.
The Ethics Committee of the same hospital where this research was carried out approved the study design.

Results
Of the 363 women selected for the study sample, 25 were excluded. Of these, 7 were excluded due to antecedents of cesarean sections, 6 due to emergency cesarean sections without labor, other 2 gave birth in a different hospital, other 7 due to premature birth, and finally, 3 due to delivery of twins. The final sample consisted of 338 women.
The average age of women in the sample was 30.80 (5.01) years, with a minimum age of 16 years and maximum of 46 years. The percentages of spontaneous births, instrumental births and cesarean sections were 67.5%, 13.9% and 18.6%, respectively. Primiparous women were 63% (n = 213) and multiparous were 37% (n = 125). In total, 6% of women (n = 20) had experienced a previous cesarean section. The percentage of women who were stimulated with oxytocin was 51.5% (n = 174). Likewise, the percentage of women receiving epidural anesthesia was 78% (n = 263). Episiotomy was performed in 39% of women (n = 133) and 11.5% (n = 39) had intrapartum fever. Early artificial rupture of membranes was performed in 48.5% of women (n = 164). The average of arterial pH of umbilical cord blood was 7.28 (0.09). These data are shown in Table 1.

Discussion
These results must be viewed with caution due to the limitations of this study. These include, that it was carried out in a single hospital, although it provides medical assistance to a large population. One might also consider that the sample is limited, which represents 8% of women treated in a year for delivery in this hospital.
Analysis of the type of delivery resulted in statistically Regarding the variable 5-min Apgar score, although in our study no significant differences were found, other authors found differences, namely a greater percentage of infants born vaginally from mothers stimulated with oxytocin, with Apgar scores per minute <= 7, compared with mothers non-submitted to stimulation (14) .
This study has also identified an association between stimulation with oxytocin and maternal intrapartum fever. However, other authors have not found enough evidence to sustain that high doses of oxytocin were related to maternal fever during labor (24) .
In another study carried out in 2012 (25) , it was found that high temperature was associated with a high body mass index and with the time elapsed from the rupture of the amniotic sac until delivery, whereas epidural analgesia did not influence on the temperature increase.
In our study, no significant association between elevated maternal temperature and epidural administration was found.
The dilation stage proved to be longer in the group of primiparous women non-submitted to stimulation with oxytocin, so this result is consistent with those of other authors, which showed that the duration of this first stage of labor was significantly shorter when the dose of oxytocin was increased (1) .

Conclusion
The results of this study show that the use of oxytocin in labor stimulation can be detrimental to both the mother and the newborn, since they indicate that the use of oxytocin is associated with increased cesarean section rates, use of epidural analgesia and maternal intrapartum fever, both in primiparous and multiparous.
Furthermore, it was also observed a significant association between stimulation with oxytocin and low pH values of umbilical cord blood of newborns of primiparous mothers.
On the other hand, coinciding with other studies, it has been proved its association with a shorter duration in the first stage of labor. However, it had no adverse effects on the rates of 3 rd and 4 th degree lacerations, episiotomies, Hidalgo-Lopezosa P, Hidalgo-Maestre M, Rodríguez-Borrego MA.
advanced neonatal resuscitation, 5-min Apgar scores and meconium in the amniotic fluid.
Therefore, we may conclude that stimulation with oxytocin should not be used systematically, but only in very specific cases, in which its use is particularly necessary.
These results provide to health professionals a better understanding of the effects of the use of oxytocin during labor, which can be useful for decision-making in clinical practice. At the same time, these results reinforce the need to reflect on a change in the delivery care paradigm. In addition, they provide information to mothers towards the acquisition of more knowledge about the delivery process, considering that pregnant women should be informed of the possible effects of the use of oxytocin for labor stimulation.