Prolongation of active second stage of labor: Associated factors and perinatal outcomes

Maternal outcomes using delayed pushing versus immediate pushing in the second stage of labour: An umbrella review

INTRODUCTION

Different systematic reviews have been developed in the last decades about maternal risks of immediate pushing and delayed pushing, depending on the duration of the second stage of labour, but they do not provide conclusive evidence.

AIM

The main aim of this overview of systematic reviews was to assess the maternal outcomes using delayed pushing and immediate pushing in the second stage of labour in women receiving epidural analgesia.

METHODS

We searched systematically in PubMed (Medline), EMBASE, CINAHL, and Scopus (October 26th, 2023). Methodological quality was analysed using AMSTAR and ROBIS scales, and the strength of evidence was established according to the guidelines advisory committee grading criteria. The outcome measures were the duration of the second stage of labour, duration of active pushing, caesarean section, instrumental vaginal birth, spontaneous vaginal birth, fatigue score, perineal lacerations, postpartum haemorrhage, and rate of episiotomy. Seven systematic reviews with and without meta-analysis were included.

RESULTS

Results showed that delayed pushing increases the total time of the second stage of labour, although delayed pushing decreases the duration of active pushing with moderate quality of evidence. Mixed results were found with respect to the variables instrumental vaginal birth, spontaneous vaginal birth, and fatigue score although the results favour delayed pushing or show no statistically significant differences with respect to immediate pushing. No favourable results were ever found for immediate pushing with respect to delayed pushing, with a limited quality of evidence. Even so, delayed pushing seems to be associated with a significant increase in spontaneous vaginal birth rates. The results found no significant differences between the immediate pushing and delayed pushing groups in the caesarean section rates, perineal lacerations, postpartum haemorrhage, and episiotomy ratio, with a limited quality of evidence.

CONCLUSIONS

This study shows that delayed pushing during the second stage of labour produces at least the same maternal outcomes as immediate pushing, although we note that delayed pushing produces an increase of the duration of the second stage of labour, a shorter duration of the active pushing and a tendency to increase spontaneous vaginal birth and to reduce the instrumental vaginal birth rates and fatigue scores. This should be considered clinically. This review was registered in the International Prospective Register of Systematic Reviews PROSPERO (CRD42023397616).

Risk factors for early postpartum hemorrhage: A retrospective, population-based, cohort analysis

OBJECTIVE

To identify risk factors for developing early postpartum hemorrhage (PPH) and to examine whether risk factors vary according to severity and mode of delivery.

METHODS

A population-based cohort study was conducted in which all deliveries at a tertiary medical center were included. Risk factors for developing early PPH were compared based on the severity of bleeding as well as the mode of delivery. Multiple logistic regression models were used to control for confounders.

RESULTS

Among 322 497 deliveries included in the analysis, early PPH complicated 1811 (0.56%) of all deliveries. Among all cases of early PPH, 505 deliveries (28%) were complicated with severe PPH. Using a logistic regression model, in vitro fertilization (IVF) pregnancy, previous cesarean delivery (CD), pre-eclampsia, placental abruption, and uterine rupture were independently associated only with severe early PPH, while non-progressive second stage of labor, induction of labor, and large for gestational age were independently associated with both severe and mild early PPH. When applying an additional logistic regression model, whereas IVF pregnancy, pre-eclampsia, and large for gestational age were independently associated with early PPH among vaginal deliveries only, placenta previa was independently associated with early PPH among CD only.

CONCLUSIONS

Independent risk factors for developing severe PPH solely include IVF pregnancy, previous CD, pre-eclampsia, placental abruption, and uterine rupture. IVF pregnancy, pre-eclampsia, and large for gestational age are independent risk factors for early PPH following vaginal delivery, while placenta previa is independently associated with early PPH after CD only. Due to the recognition of the importance of both the provider and institutional planning and preparation for PPH, the study's results should be viewed within the scope of its retrospective cohort design.

Fetal oxygenation in the last weeks of pregnancy evaluated through the umbilical cord blood gas analysis

Introduction

Embryo and fetus grow and mature over the first trimester of pregnancy in a dynamic hypoxic environment, where placenta development assures an increased oxygen availability. However, it is unclear whether and how oxygenation changes in the later trimesters and, more specifically, in the last weeks of pregnancy.

Methods

Observational study that evaluated the gas analysis of the umbilical cord blood collected from a cohort of healthy newborns with gestational age ≥37 weeks. Umbilical venous and arterial oxygen levels as well as fetal oxygen extraction were calculated to establish whether oxygenation level changes over the last weeks of pregnancy. In addition, fetal lactate, and carbon dioxide production were analyzed to establish whether oxygen oscillations may induce metabolic effects in utero.

Results

This study demonstrates a progressive increase in fetal oxygenation levels from the 37th to the 41st weeks of gestation (mean venous PaO₂ approximately from 20 to 25 mmHg; p < 0.001). This increase is largely attributable to growing umbilical venous PaO₂, regardless of delivery modalities. In neonates born by vaginal delivery, the increased oxygen availability is associated with a modest increase in oxygen extraction, while in neonates born by cesarean section, it is associated with reduced lactate production. Independently from the type of delivery, carbon dioxide production moderately increased. These findings suggest a progressive shift from a prevalent anaerobic metabolism (Warburg effect) towards a growing aerobic metabolism.

Conclusion

This study confirms that fetuses grow in a hypoxic environment that becomes progressively less hypoxic in the last weeks of gestation. The increased oxygen availability seems to favor aerobic metabolic shift during the last weeks of intrauterine life; we hypothesize that this environmental change may have implications for fetal maturation during intrauterine life.