Duration of Second Stage of Labour and Maternal Outcome

Background: The second stage of labour begins from full dilatation of the cervix up to the birth of the singleton baby or the last baby in a multiple pregnancy entailing a process of descent, rotation and expulsive or propulsive efforts. The ideal management of the second stage should maximize the probability of vaginal delivery while minimizing the risks of maternal morbidity and mortality. Objective: The main objective of this study is to determine the relationship between the duration of the second stage of labour and adverse maternal outcomes. Methods: Facility based prospective cohort study design was employed on women who delivered in four teaching hospitals from January 1 to


Introduction
The conventional 2-hour rule of the second stage of labour dates to the 1800's and is defined as the period between full cervical dilatation of 10 cm and the birth of the baby [1][2][3][4]. In doing so, there is constant descent of the presenting part along with the processes of flexion and rotation in conformity to the shape of the pelvic passage culminating with the woman's involuntary urge to bear down as a result of increased intra-abdominal pressure and expulsive uterine contractions and finally giving birth. Abnormal labour is more associated with a conundrum of semantic issues (abnormal labour, dystocia, protraction disorder, arrest disorder) implying failure to progress and an abnormally long latent phase or second stage that is described as prolonged deviating from the usual description of normal labour. Although labour is regarded as a physiological phenomenon, there is a tremendous work output, energy expenditure, fluid and electrolyte imbalances and physical exhaustion as well as alterations in the psyche of the parturient.
The epidemiology of the length of labour was reported by Friedman in several landmark articles over 60 years ago that are very much respectfully and academically accepted to date [2,3].
These studies changed modern obstetrics; most specifically, they led to specific normative guidelines on the length of the first and second stages of labour. It is very recently that the ACOG had modified and defined prolonged second stage in nulliparous patients as a lack of continuing progress for 3 hours with regional anaesthesia or 2 hours without regional anaesthesia; for multiparous patients, a lack of progress for 2 hours with or 1 hour without regional anaesthesia [4]. It is recommended by the WHO that the women should be informed of the reality that the duration of the second stage varies from one woman to another and in that in the first labours, birth is usually completed within 3 hours whereas in subsequent labours, birth is usually effected within 2 hours [5].
The clinical practice dictates that as the duration of second stage of labour increases, there are likelihoods to encounter increased risk of a multitude of maternal and neonatal morbidity [6][7][8][9]. Retrospective chart reviews and cohort studies demonstrated that there exist a possibility of difficult cesarean sections andinstrumental vaginal deliveries with resultant maternal morbidities like postpartum haemorrhage, uterine atony, severe obstetric lacerations, chorioamnionitis, puerperal sepsis and third or fourth-degree perineal lacerations with most prolonged second stages of labour [4,[10][11][12][13][14][15]. The second stage of labor is regarded as the climax of the birth by the delivering woman, her partner, and the care provider [16]. It has been thought of as a time of particular asphyxial risk for the fetus and maternal morbidity. The perceived risks have been invoked to justify arbitrary time limits and high rates of interferences including operative vaginal and abdominal deliveries [10,17,18]. The second stage of labor is often regarded as a time when mother and obstetrician are physically and mentally exhausted and there is a great temptation to "do something" to end the labor [17]. There is no study done in Ethiopia that evaluated the effect of duration of second stage of labour on maternal outcome.
Thus, the study will shade light into this important issue, serve as a reference and contribute to a much larger scale of nationwide undertakings. We would like to bring forth our intention of treating perinatal outcome separately in the light of the bulky nature of the study and avoid undue congestion of data.

Materials and Methods
This facility-based prospective cohort study of women in labour who reached second stage was conducted in four teaching government hospitals in Addis Ababa from January 1 to July 30, 21019. The four teaching hospitals are Tikur Anbesa Specialized Hospital (TASH), Gandhi Memorial Hospital (GMH), Zewditu Memorial Hospital (ZMH) and Yekatit 12 Hospital (Y 12 H). It is to be noted that the institutions have ante partum, intra partum and postpartum services for obstetric patients. Their delivery wards have active pre-labour beds, second stage rooms, delivery couches and neonatal resuscitation rooms with radiant heater, oxygen and suction machine. They are invariably staffed by midwives, interns, residents and consultants. This cohort study design was employed on all women with pregnancy beyond 37 gestational weeks (term, post term, vertex) with live and singleton births who reached or otherwise were referred to in second stage of labour and delivered in the four teaching hospitals. All the parturient who did not fulfill these criteria including those with underlying medical complications warranting immediate delivery, who came from home or referring centers at second stage were excluded from the study.
The minimum cohort sample size was determined using Epiinfo stat-calc using, as a reference, an article by Yueh Chang Kuo and et al. [19]. A sample size of 1550 for the exposed and nonexposed each making for the total sample size of 3100 was initially calculated. Adding a 10% non-response rate of 310 for the total sample size, the sum was put at 3410. We found it convenient and opted for more cases bringing up the final sample size to 3776.
The independent variables analyzed included socio-demographic characteristic, gravidity, parity, gestational age, birth weight, mode of delivery and antenatal complications (PROM, chorioamnionitis, hypertension, gestational diabetes, cesarean scar…) whereas the dependent variables of importance were maternal outcomes that included postpartum haemorrhage (estimated blood loss of > 500 ml or 10% drop in haematocrit after delivery ), chorioamnionitis, perineal trauma (third-or fourth-degree lacerations), operative vaginal delivery and Cesarean delivery.
Mean with standard deviation for quantitative variable, percentage and proportion for qualitative variable was analyzed.
To control the effect of confounding variables, stepwise multiple logistic regression analysis was carried out and Adjusted Odds Ratios (AORs) employed to explore the real association. A confidence limit of 95% and p-value less than 0.05 was used as cut of point to see presence of statistical significance. Chi square and Fisher exact test was also used for categorical variables. The maternal data were collected by the principal investigator and trained health care  (Table 1). Of the study population, 2897 (76.7%) had ANC follow up at HC and were referred to hospitals for delivery for different reasons.
The reason for referral was not clearly described in 2156(74.5%) except for the statement "for better care" (  Of the total study subjects who had complications; 28(0.7%) had uterine atony, 10(0.3%) major degree perineal tear, 12(0.3%) of the mothers had pre and postpartum hematocrit difference of ≥10%.
EBL>500ml was found in 121(3.2%) of the total studied subjects, the overall rate of PPH in the study population was 125(3.3%). As parity increased, hematocrit values of the mothers at admission registered at significantly the lower levels (P<0.001) compared to the low parity or nulipara. There was no significant association in antenatal morbidity with parity (P=0.905). As parity increased, duration of labor and duration of SSOL significantly decreased for both (P<0.001). As parity increased, it was shown that weight of the baby also significantly increased (P<0.001). There was statistically significant positive correlation between parity and maternal morbidity, as a higher parity resulted in increased maternal    minutes is approximately comparable with the study done that showed the mean duration of the second stage of labour to be 70min (range 2-387, SD +73min) [20].

Discussion
Concerning the nullipara, the mean duration of SSOL was 69.4min±47.4 (5-330) min. This is much shorter when compared to the most recent study done by Sandström which stated that, the median duration of second stage of labour was 93 min and 95% were delivered within 272 min (4.5 h) [22]. This variation could partly be explained by the difference in the studied population and the local policy and guidelines of the management of labour.
It was also observed that only 15.8% of the mothers in this study delivered within 30minuts, 55.8% within an hour and 86.3% within 2hours after they reached SSOL. This is contrary to the study done by Duignan which states that even 83% of the primiparas gave birth within an hour and 98.5% of multipara delivered with in 2 hour [23]. Nevertheless, it is similar to Friedman's study which evaluated the natural course of labour and noted that most nulliparous women without epidural anesthesia delivered within 2 hours [2,3].
In our study, only 2.9% of the labouring mothers stayed for more than 3 hours in SSOL. This is in contrast to the publication by Allen et al. where it is stated that 14.8% of nulliparous women were identified as having a second stage of labour duration longer than 3 hours and 3.2% of multiparous women were identified as having a second stage of labour duration of longer than 2 hours [24]. We have also observed that as maternal age and parity increases duration of SSOL significantly decreases. This is also true for most of the studies done previously [12,19,23]. As shown in our study, EBL had a statistically significant association with duration of SSOL. PPH is more common in those mothers whose duration of SSOL is ≥2hr compared to ≤1hr 9.2% vs. 1.8%. This association is also seen in another study that showed that there is slight increase in PPH after duration of SSOL is extended beyond 2 hours, but the association is more significant after the duration of SSOL is more than 3 hours [25]. Our finding showed that increased blood loss is more common among mothers delivered by operative means compared to SVD at any time; and other studies also reported the same [24].  23.5% in those mothers who stayed in SSOL for more than 4 hours [12]. The study in Munich showed higher results; patients with a prolonged second stage of labour sustained such a tear significantly more often (7.7%) than patients with a normal duration of second stage (2.9%). The highest incidence of these tears was observed in patients with duration of the second stage longer than 4hr (12.8%).
Patients with a vaginal operative delivery suffered significantly more often from a third-degree sphincter tear (9.3%) than patients with a spontaneous delivery 2.9% [20]. Unlike the setups in the more advanced countries where there exist the personnel, the finance, the infrastructure, logistics including medicines and gadgets like fetal electrocardiography, cardiotocography, strict policies in implementing partographs and rules and regulations in place pertaining to one-to-one follow up and monitoring during labour that obviously highlight the differences and accentuates the reasons for undertaking such a study. This study will generate evidence on effect of duration of second stage on maternal outcome in our setup that would serve as future building blocks.