Length of second stage of labor and preterm birth in a subsequent pregnancy

The use of bubble charts in analyzing second stage cesarean delivery rates

BACKGROUND

The incidence of second stage cesarean delivery has been rising globally because of the failure or the anticipated difficulty of performing instrumental delivery. Yet, the best way to interpret the figure and its optimal rate remain to be determined. This is because it is strongly influenced by the practice of other 2 modes of birth, namely cesarean delivery performed before reaching the second stage and assisted vaginal birth during the second stage. In this regard, a bubble chart that can display 3-dimensional data through its x-axis, y-axis, and the size of each plot (presented as a bubble) may be a suitable method to evaluate the relationship between the rates of these 3 modes of births.

OBJECTIVE

This study aimed to conduct an epidemiologic study on the incidence of second stage cesarean deliveries rates among >300,000 singleton term births in 10 years from 8 obstetrical units and to compare their second stage cesarean delivery rates in relation to their pre-second stage cesarean delivery rates and assisted vaginal birth rates using a bubble chart.

STUDY DESIGN

The territory-wide birth data collected between 2009 and 2018 from all 8 public obstetrical units (labelled as A to H) were reviewed. The inclusion criteria were all singleton pregnancies with cephalic presentation that were delivered at term (≥37 weeks' gestation). Pre-second stage cesarean delivery rate was defined as all elective cesarean deliveries and those emergency cesarean deliveries that occurred before full cervical dilatation was achieved as a proportion of the total number of births. The second stage cesarean delivery rate and assisted vaginal birth rate were calculated according to the respective mode of delivery as a proportion of the number of cases that reached full cervical dilatation. The rates of these 3 modes of births were compared among the parity groups and among the 8 units. Using a bubble chart, each unit's second stage cesarean delivery rate (y-axis) was plotted against its pre-second stage cesarean delivery rate (x-axis) as a bubble. Each unit's second stage cesarean delivery to assisted vaginal birth ratio was represented by the size of the bubble.

RESULTS

During the study period, a total of 353,434 singleton cephalic presenting term pregnancies were delivered in the 8 units, and 180,496 (51.1%) were from nulliparous mothers. When compared with the multiparous group, the nulliparous group had a significantly lower pre-second stage cesarean delivery rate (18.58% vs 21.26%; P<.001) but a higher second stage cesarean delivery rate (0.79% vs 0.22%; P<.001) and a higher assisted vaginal birth rate (17.61% vs 3.58%; P<.001). Using the bubble of their averages as a reference point in the bubble chart, the 8 units' bubbles were clustered into 5 regions indicating their differences in practice: unit B and unit H were close to the average in the center. Unit A and unit F were at the upper right corner with a higher pre-second stage cesarean delivery rate and second stage cesarean delivery rate. Unit D and unit E were at the opposite end. Unit C was at the upper left corner with a low pre-second stage cesarean delivery rate but a high second stage cesarean delivery rate, whereas unit G was at the opposite end. Unit C and unit G were also in the extremes in terms of pre-second stage cesarean delivery to assisted vaginal birth ratio (0.09 and 0.01, respectively). Although some units seemed to have very similar second stage cesarean delivery rates, their obstetrical practices were differentiated by the bubble chart.

CONCLUSION

The second stage cesarean delivery rate must be evaluated in the context of the rates of pre-second stage cesarean delivery and assisted vaginal birth. A bubble chart is a useful method for analyzing the relationship among these 3 variables to differentiate the obstetrical practice between different units.

Operative delivery in the second stage of labor and preterm birth in a subsequent pregnancy: a systematic review and meta-analysis

OBJECTIVE

This study aimed to quantify the association between mode of operative delivery in the second stage of labor (cesarean delivery vs operative vaginal delivery) and spontaneous preterm birth in a subsequent pregnancy.

DATA SOURCES

MEDLINE, Embase, EmCare, CINAHL, the Cochrane Library, Web of Science: Core Collection, and Scopus were searched from database inception to April 1, 2023.

STUDY ELIGIBILITY CRITERIA

All retrospective cohort studies with participants who had a second-stage cesarean delivery (defined as intrapartum cesarean delivery at full cervical dilation) or operative vaginal delivery (including forceps- and/or vacuum-assisted delivery) and that reported the rate of preterm birth (either spontaneous or not specified) in subsequent pregnancy were included.

METHODS

Both a descriptive analysis and a meta-analysis were performed. A meta-analysis was performed for dichotomous data using the Mantel-Haenszel random-effects model and used the odds ratio as an effect measure with 95% confidence intervals. The risk of bias was assessed using Cochrane's 2022 Risk Of Bias In Non-randomized Studies of Exposure tool.

RESULTS

After screening 2671 articles from 7 databases, a total of 18 retrospective cohort studies encompassing 605,138 patients were included. The pooled rates of spontaneous preterm birth in a subsequent pregnancy were 6.9% (12 studies) after second-stage cesarean delivery and 2.6% (8 studies) after operative vaginal delivery. A total of 7 studies encompassing 75,460 patients compared the primary outcome of spontaneous preterm birth after second-stage cesarean delivery vs operative vaginal delivery in an index pregnancy with an odds ratio of 2.01 (95% confidence interval, 1.57-2.58) in favor of operative vaginal delivery. However, most studies did not include important confounding factors, did not address exposure misclassification because of failed operative vaginal delivery, and considered operative vaginal delivery as a homogeneous category with no distinction between forceps- and vacuum-assisted deliveries.

CONCLUSION

Although a synthesis of the existing literature suggests that the risk of spontaneous preterm birth is higher in those with a previous second-stage cesarean delivery than in those with operative vaginal delivery, the risk of bias in these studies is very high. Findings should be interpreted with caution.

Risk of spontaneous preterm birth elevated after first cesarean delivery at full dilatation: a retrospective cohort study of over 30,000 women

BACKGROUND

Having a cesarean delivery at full dilatation has been associated with increased subsequent risk of spontaneous preterm birth. The Aberdeen Maternity and Neonatal Databank provides a rare opportunity to study subsequent pregnancy outcomes after a previous cesarean delivery at full dilatation over 40 years, with an ability to include a detailed evaluation of potential confounding factors.

OBJECTIVE

This study aimed to investigate if having an initial cesarean delivery at full dilatation is associated with spontaneous preterm birth or other adverse pregnancy outcomes in the subsequent pregnancy.

STUDY DESIGN

A retrospective cohort study was conducted including women with a first and second pregnancy recorded within the Aberdeen Maternity and Neonatal Databank between 1976 and 2017, where previous cesarean delivery at full dilatation at term in the first birth was the exposure. The primary outcome was spontaneous preterm birth (defined as spontaneous birth <37 weeks). Multivariate logistic regression was used to investigate any association between cesarean delivery at full dilatation and the odds of spontaneous preterm birth. Cesarean delivery at full dilatation in previous pregnancy was compared with: (1) any other mode of birth, and (2) individual modes of birth, including planned cesarean delivery, cesarean delivery in first stage of labor (<10-cm dilatation), and vaginal birth (including spontaneous vaginal birth, nonrotational forceps, Kielland forceps, vacuum-assisted birth, breech vaginal birth). Other outcomes such as antepartum hemorrhage and mode of second birth were also compared.

RESULTS

Of the 30,253 women included, 900 had a previous cesarean delivery at full dilatation in the first pregnancy. Women with previous cesarean delivery at full dilatation had a 3-fold increased risk of spontaneous preterm birth in a second pregnancy (unadjusted odds ratio, 2.63; 95% confidence interval, 1.82-3.81; adjusted odds ratio, 3.31; 95% confidence interval, 2.17-5.05) compared with those with all other modes of first birth, adjusted for maternal age, diabetes mellitus, body mass index, smoking, preeclampsia, antepartum hemorrhage, socioeconomic deprivation (Scottish Index of Multiple Deprivation 2016), year of birth, and interpregnancy interval (in second pregnancy). When compared with women with vaginal births only, women with cesarean delivery at full dilatation had 5-fold increased odds of spontaneous preterm birth (adjusted odds ratio, 5.37; 95% confidence interval, 3.40-8.48). Compared with first spontaneous vaginal birth, first instrumental births (nonrotational forceps, Kielland forceps, and vacuum births) were not associated with increased risk of spontaneous preterm birth in the second birth. After an initial cesarean delivery at full dilatation, 3.7% of women had a repeated cesarean delivery at full dilatation and 48% had a planned cesarean delivery in the second birth.

CONCLUSION

This study is a substantial addition to the body of evidence on the risk of subsequent spontaneous preterm birth after cesarean delivery at full dilatation, and demonstrates a strong association between cesarean delivery at full dilatation in the first birth and spontaneous preterm birth in subsequent pregnancy, although the absolute risk remains small. This is a large retrospective cohort and includes a comprehensive assessment of potential confounding factors, including preeclampsia, antepartum hemorrhage, and lengths of first and second stage of labor. Future research should focus on understanding possible causality and developing primary and secondary preventative measures.

The use of bubble charts in analyzing the global second-stage cesarean delivery rates: a systematic review

OBJECTIVE

This study aimed to systematically review the worldwide second-stage cesarean delivery rate concerning pre-second-stage cesarean delivery and assisted vaginal birth rates.

DATA SOURCES

PubMed, Medline Ovid, EBSCOhost, Embase, Scopus, and Google Scholar were queried from inception to February 2023, with the following terms: "full dilatation," "second stage," and "cesarean," with their word variations. Furthermore, an additional cohort of 353,434 cases from our recently published study was included.

STUDY ELIGIBILITY CRITERIA

Only original studies that provided sufficient information on the number of pre-second-stage cesarean deliveries, second-stage cesarean deliveries, and vaginal births were included for the calculation of different modes of delivery. Systemic reviews, meta-analyses, or case reports were excluded.

METHODS

Study identification and data extraction were independently performed by 2 authors. Selected studies were categorized on the basis of parity, study period, and geographic regions for comparison.

RESULTS

A total of 25 studies were included. The overall pre-second-stage cesarean delivery rate, the second-stage cesarean delivery rate, and the second-stage cesarean delivery-to-assisted vaginal birth ratio were 17.94%, 2.65%, and 0.19, respectively. Only 5 studies described singleton, term, cephalic presenting pregnancies of nulliparous women, and their second-stage cesarean delivery rates were significantly higher than those studies with cohorts of all parity groups (4.50% vs 0.83%; P<.05). In addition, the second-stage cesarean delivery rate showed a secular increase across 2009 (0.70% vs 1.05%; P<.05). Moreover, it was the highest among African studies (5.14%) but the lowest among studies from East Asia and South Asia (0.94%). The distributions of second-stage cesarean delivery rates of individual studies and subgroups were shown with that of pre-second-stage cesarean delivery and assisted vaginal birth using the bubble chart.

CONCLUSION

The overall worldwide pre-second-stage cesarean delivery rate was 17.94%, the second-stage cesarean delivery rate was 2.65%, and the second-stage cesarean delivery-to-assisted vaginal birth ratio was 0.19. The African studies had the highest second-stage cesarean delivery rate (5.14%) and second-stage cesarean delivery-to-assisted vaginal birth ratio (1.88), whereas the studies from East Asia and South Asia were opposite (0.94% and 0.11, respectively).

Cesarean Uterine Lacerations and Prematurity in the Following Delivery: A Retrospective Longitudinal Follow-Up Cohort Study

(1) Background: We aimed to investigate whether second-stage cesarean delivery (SSCD) had a higher occurrence of low-segment uterine incision extensions compared with cesarean delivery (CD) at other stages of labor and to study the association of these extensions with preterm birth (PTB). (2) Methods: In this retrospective longitudinal follow-up cohort study, spanning from 2006 to 2019, all selected mothers who delivered by CD at first birth (P1) and returned for second birth (P2) were grouped by cesarean stage at P1: planned CD, first-stage CD, or SSCD. Mothers with a PTB at P1, multiple-gestation pregnancies in either P1 or P2 and those with prior abortions were excluded. (3) Results: The study included 1574 selected women who underwent a planned CD at P1 (n = 483 (30.7%)), first-stage CD (n = 878 (55.8%), and SSCD (n = 213 (13.5%)). There was a higher occurrence of low-segment uterine incision extensions among SSCD patients compared to first-stage CDs and planned CDs: 50/213 (23%), 56/878 (6.4%), and 5/483 (1%), respectively (p < 0.001). A multivariate logistic regression showed that women undergoing an SSCD are at risk for low-segment uterine incision extensions compared with women undergoing a planned CD, OR 28.8 (CI 11.2; 74.4). We observed no association between the occurrence of a low-segment uterine incisional extension at P1 and PTB ≤ 37 gestational weeks in the subsequent delivery, with rates of 6.3% (7/111) for those with an extension compared to 4.5% (67/1463) for those without an extension (p = 0.41). Notably, parturients experiencing a low-segment uterine incisional extension during their first childbirth were six times more likely to have a preterm delivery before 32 weeks of gestation compared to those without extensions, with two cases (1.8%) compared to four cases (0.3%), respectively. A similar trend was observed for preterm deliveries between 32 and 34 weeks of gestation, with those having extensions showing twice the prevalence of prematurity compared to those without, with a p-value of 0.047. (4) Conclusions: This study highlights that mothers undergoing SSCD experience higher prevalence of low uterine incision extensions compared to other CDs. To further ascertain whether the presence of these extensions is associated with preterm birth (PTB) in subsequent births, particularly early PTB before 34 weeks of gestation, larger-scale future studies are warranted.

Failed vacuum and preterm delivery risk in the subsequent pregnancy: a multicenter retrospective cohort study

BACKGROUND

Second-stage cesarean delivery is associated with subsequent preterm delivery. Failed vacuum-assisted delivery is a subgroup of second-stage cesarean delivery in which the fetal head is engaged deeper in the pelvis and, thus, is associated with an increased risk of short-term maternal complications.

OBJECTIVE

This study aimed to investigate the maternal and neonatal outcomes of women at their subsequent delivery after a second-stage cesarean delivery with failed vacuum-assisted extraction vs after a second-stage cesarean delivery without a trial of vacuum-assisted extraction.

STUDY DESIGN

This was a multicenter retrospective cohort study. The study population included all women in their subsequent pregnancy after a second-stage cesarean delivery who delivered in all university-affiliated obstetrical centers (n=4) in a single geographic area between 2003 and 2021. Maternal and neonatal outcomes of women who had second-stage cesarean delivery after a failed vacuum-assisted delivery were compared with women who had second-stage cesarean delivery without a trial of vacuum-assisted delivery. The primary outcome of this study was preterm delivery at <37 weeks of gestation. The secondary outcomes were vaginal birth rate and other adverse maternal and neonatal outcomes. Univariate analysis was followed by multiple logistic regression modeling.

RESULTS

During the study period, 1313 women met the inclusion criteria, of whom 215 (16.4%) had a history of failed vacuum-assisted delivery at the previous delivery and 1098 (83.6%) did not. In univariate analysis, women with previously failed vacuum-assisted delivery had similar preterm delivery rates (<37, <34, <32, and <28 weeks of gestation), a successful trial of labor after cesarean delivery rates, uterine rupture, and hysterectomy. However, multivariable analyses controlling for confounders showed that a history of failed vacuum-assisted delivery is associated with a higher risk of preterm delivery at <37 weeks of gestation (adjusted odds ratio, 2.05; 95% confidence interval, 1.11-3.79; P=.02), but not with preterm delivery at <34 or <32 weeks of gestation.

CONCLUSION

Among women with a previous second-stage cesarean delivery, previously failed vacuum-assisted delivery was associated with an increased risk of preterm delivery at <37 weeks of gestation in the subsequent birth.

Identification of risk factors for incident cervical insufficiency in nulliparous and parous women: a population-based case-control study

BACKGROUND

Cervical insufficiency is one of the underlying causes of late miscarriage and preterm birth. Although many risk factors have been identified, the relative magnitude of their association with risk in nulliparous versus parous women has not been well demonstrated, especially for incident cervical insufficiency (ICI). The aim of this study was to investigate and compare the magnitude of the association of ICI with predictive factors in nulliparous and parous women, and to further investigate various aspects of obstetric history for parous women.

METHODS

Pregnant women with a first diagnosis of cervical insufficiency were compared to a random sample of control pregnancies from women with no diagnosis by using Swedish national health registers. Demographic, reproductive, and pregnancy-specific factors were compared in case and control pregnancies, and relative risks presented as odds ratios (OR), stratified by nulliparous/parous. Independent associations with ICI were estimated from multivariable logistic regression. Associations with obstetric history were further estimated for multiparous women.

RESULTS

A total of 759 nulliparous ICI cases and 1498 parous cases were identified during the study period. Multifetal gestation had a strong positive association with ICI in both groups, but of much larger magnitude for nulliparous women. The number of previous miscarriages was also a much stronger predictor of risk in nulliparous women, especially for multifetal pregnancies. History of preterm delivery (<37 weeks' gestation) was an independent predictor for parous women, and for those whose most recent delivery was preterm, the association with ICI increased with each additional week of prematurity. A previous delivery with prolonged second stage of labor or delivery of a very large infant were both inversely associated with risk of ICI in the current pregnancy.

CONCLUSIONS

The differences in importance of predictive risk factors for incident cervical insufficiency in nulliparous and parous women can help resolve some of the inconsistencies in the literature to date regarding factors that are useful for risk prediction. Stratifying on parity can inform more targeted surveillance of at-risk pregnancies, enable the two groups of women to be better informed of their risks, and eventually inform screening and intervention efforts.

Reproducibility of assessment of full-dilatation Cesarean section scar in women undergoing second-trimester screening for preterm birth

OBJECTIVE

To assess the reproducibility of a standardized method of measuring the Cesarean section (CS) scar, CS scar niche and their position relative to the internal os of the uterine cervix by transvaginal ultrasound in pregnant women with a previous full-dilatation CS.

METHODS

This was a prospective, single-center reproducibility study on women with a singleton pregnancy and a previous full-dilatation CS who underwent transvaginal ultrasound assessment of cervical length and CS scar characteristics at 14-24 weeks' gestation. The CS scar was identified as a hypoechogenic linear discontinuity of the myometrium at the anterior wall of the lower uterine segment or cervix. The CS scar niche was identified as an indentation at the site of the scar with a depth of at least 2 mm. The CS scar position was evaluated by measuring the distance to the internal cervical os. CS scar niche parameters, including its length, depth, width, and residual and adjacent myometrial thickness, were assessed in the sagittal and transverse planes. Qualitative reproducibility was assessed by agreement regarding visibility of the CS scar and niche. Quantitative reproducibility of CS scar measurements was assessed using three sets of images: (1) real-time two-dimensional (2D) images (real-time acquisition and caliper placement on 2D images by two operators), (2) offline 2D still images (offline caliper placement by two operators on stored 2D images acquired by one operator) and (3) three-dimensional (3D) volume images (volume manipulation and caliper placement on 2D images extracted by two operators). Agreement on CS scar visibility and the presence of a niche was analyzed using kappa coefficients. Intraobserver and interobserver reproducibility of quantitative measurements was assessed using Bland-Altman plots.

RESULTS

To achieve the desired statistical power, 72 women were recruited. The CS scar was visualized in > 80% of images. Interobserver agreement for scar visualization and presence of a niche in real-time 2D images was excellent (kappa coefficients of 0.84 and 0.85, respectively). Overall, reproducibility was higher for real-time 2D and offline 2D still images than for 3D volume images. The 95% limits of agreement (LOA) for intraobserver reproducibility were between ± 1.1 and ± 3.6 mm for all sets of images; the 95% LOA for interobserver reproducibility were between ± 2.0 and ± 6.3 mm. Measurement of the distance from the CS scar to the internal cervical os was the most reproducible 2D measurement (intraobserver and interobserver 95% LOA within ± 1.6 and ± 2.7 mm, respectively). Overall, niche measurements were the least reproducible measurements (intraobserver 95% LOA between ± 1.6 and ± 3.6 mm; interobserver 95% LOA between ± 3.1 and ± 6.3 mm). There was no consistent difference between measurements obtained by reacquisition of 2D images (planes obtained twice and caliper placed), caliper placement on 2D stored images or volume manipulation (planes obtained twice and caliper placed).

CONCLUSIONS

The CS scar position and scar niche in pregnant women with a previous full-dilatation CS can be assessed in the second trimester of a subsequent pregnancy using either 2D or 3D volume ultrasound imaging with a high level of reproducibility. Overall, the most reproducible CS scar parameter is the distance from the CS scar to the internal cervical os. The method proposed in this study should enable clinicians to assess the CS scar reliably and may help predict pregnancy outcome. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Fetal station at caesarean section and risk of subsequent preterm birth - A cohort study

OBJECTIVES

An increased risk of preterm birth (PTB) following a caesarean section (CS) in the second stage of labor has been demonstrated. We aimed to investigate the relationship between the station of the presenting fetal part and the surgical technique at first CS, and the risk of subsequent PTB.

STUDY DESIGN

This was a cohort study of 11,850 women in Sweden, delivered by CS in 2001-2007 at any of 23 birth units, with a second delivery in 2001-2009. Clinical information was retrieved from electronic birth records linked to national health registers. The risk of subsequent PTB was analyzed by fetal station, defined as low (at or below the ischial spines) or high (above the ischial spines), and aspects of the surgical technique at index CS. Associations were explored with logistic regression and results are presented as odds ratios (ORs) with 95% confidence intervals (CIs), by type and severity (very early < 32 gestational weeks and moderate preterm 32-36 gestational weeks) of PTB. Multiple logistic regression included adjustments for maternal age, gestational age at first delivery, and inter-delivery interval.

RESULTS

Out of 11,850 women delivered by CS, 1,016 (8.6%) delivered preterm in their subsequent pregnancy. There was an increased likelihood of spontaneous PTB, but not with medically indicated PTB, after an index CS with the fetal presenting part at a low station (aOR 1.61, 95% CI 1.23-2.11). CS performed at a low station was associated with birth < 32 gestational weeks (aOR 1.73, 95% CI 1.05-2.84) and birth at 32-36 gestational weeks (aOR 1.29, 95% CI 1.00-1.65), compared with high fetal station. Thickness of the uterine wall, incision type, and closure of the uterus at index CS did not affect the risk.

CONCLUSION

A primary CS at a low station was associated with a subsequent spontaneous PTB, but not medically indicated PTB. Surgical technique at index CS did not alter the risk.

Second stage cesarean section and the risk of preterm birth in subsequent pregnancies

OBJECTIVE

To evaluate the risk of spontaneous preterm birth on subsequent pregnancies after second stage cesarean section.

METHODS

This is a retrospective cohort study. Women were included if they had their two consecutive births in Toulouse University Hospital in the study period. The first birth was a singleton livebirth at term (≥37 weeks of gestation), divided in three categories according to the mode of delivery: vaginal delivery (group A), cesarean section before the second stage of labor (group B), cesarean section during the second stage of labor (group C). The subsequent pregnancy was the first subsequent pregnancy, conducted after 16 weeks of gestation. The primary outcome was spontaneous preterm birth in the subsequent pregnancy, defined as delivery before 37 weeks of gestation. Secondary endpoints included preterm rupture of membranes in the subsequent pregnancy.

RESULTS

Between 2003 and 2018, 7776 women (84.7%) in group A, 1263 (13.8%) in group B and 143 (1.5%) in group C were included. The adjusted odds ratio of spontaneous preterm birth before 37 weeks of gestation after second stage cesarean section was 2.4 (group C vs group A + B, 95% confidence interval: 1.2-4.8), P = 0.01). The rate of preterm rupture of membranes was also significantly higher in group C (6% vs 2% in group A, P = 0.009, 6% vs 3% in group B, P= 0.05) with OR = 3.0 (group C vs group A + B, 95% CI: 1.55-6.16, P < 0.001).

CONCLUSION

History of term second stage of labor cesarean section is an independent risk factor for spontaneous preterm birth and for preterm rupture of membrane in the subsequent pregnancy.

Prevalence and Factors Associated with Low Birth Weight and Preterm Delivery in the Ho Municipality of Ghana

Background. Low birth weight and preterm delivery are birth outcomes that can predict newborns’ survival, development, and long-term health outcomes. This study assessed the prevalence and factors associated with low birth weight and preterm delivery in the Ho Municipality of Ghana. Methods. This retrospective, cross-sectional study analysed data from 680 birth records between October and December 2018. Univariate and multivariate logistic regression models predicted low birth weight and preterm delivery factors. Results. The prevalence of low birth weight and preterm delivery was 12.9% and 14.1%, respectively. Increasing maternal age (AOR: 0.52; 95% CI: 0.28–0.98), multiparity (AOR: 0.54; 95% CI: 0.30–0.94) and increasing doses of sulphadoxine-pyrimethamine (AOR: 0.43; 95% CI: 0.22–0.84) significantly reduced the odds of low birth weight. However, caesarean section (AOR: 1.94; 95% CI: 0.1.16–3.27) and hypertension (AOR: 2.06; 95% CI: 1.27–03.33) significantly increased the likelihood of low birth weight. An increasing number of antenatal care visits (AOR: 0.38; 95% CI: 0.18–0.80) and doses of sulphadoxine-pyrimethamine (AOR: 0.43; 95% CI: 0.19–0.97) were significantly associated with decreased odds of preterm delivery, while caesarean section increased the odds of preterm delivery by two folds (AOR: 2.14; 95% CI: 1.15–3.99). Conclusion. This study shows that maternal age, parity, number of antenatal care visits, hypertension, SP/IPTp, and caesarean section were independently associated with low birth weight and preterm delivery. Education and interventions should be prioritised as vitally important on these factors to reduce the risk and complications associated with these birth outcomes.

Previous term emergency caesarean section is a risk factor for recurrent spontaneous preterm birth; a retrospective cohort study

OBJECTIVES

Emergency caesarean sections (EmCS), particularly those performed in the second stage of labour, have been associated with a risk of subsequent preterm birth. More worrying is that the risk of sPTB recurrence appears to be high in women who have had a second stage EmCS and a subsequent sPTB. However, there is a paucity of evidence regarding the risk of recurrence in women who have had a prior term EmCS at any stage of labour followed by a sPTB. This study aims to investigate the relationship between all term in labour EmCS and the risk of recurrent spontaneous preterm birth (sPTB).

STUDY DESIGN

This is an observational, retrospective cohort study conducted at St Thomas' Hospital, a tertiary-level maternity hospital in London, United Kingdom. 259 women were included; 59 women with a term in labour EmCS preceding a sPTB (EmCS group) and 200 women with a prior sPTB only (control group). The initial EmCS was further categorised into first stage (FS)-EmCS or second stage (SS)-EmCS. Primary outcome was sPTB in Pregnancy C < 37 weeks' gestation. Secondary outcomes included sPTB < 34 weeks' and < 24 weeks' gestation.

RESULTS

54% (32/59) of the EmCS group had a recurrent sPTB < 37 weeks compared to 20% (40/200) of the control women (p < 0.0001) with a relative risk of 2.71 [95%CI 1.87-3.87]). Of women who had a SS-EmCS and a subsequent PTB, 61.9% (13/21) had a further sPTB (RR 3.0 [95%CI, 1.8-4.5] compared to control women). In addition, there is nearly a 6-fold increased risk of a recurrent sPTB or midtrimester loss < 24 weeks' gestation in these women (RR 5.65 [95%CI2.6-12.0]).

CONCLUSIONS

In women who have had a previous sPTB in which a term in labour EmCS is a risk factor, the risk of a further sPTB is much higher than in those women where a prior sPTB is the sole risk factor. Furthermore, EmCS at both the first and second stage of labour are associated with a increased risk of recurrent sPTB. Further work should ascertain which women who have had a prior term EmCS are at risk of sPTB and recurrence, and how best to identify and treat them.

Duration of the second stage of labour and risk of subsequent spontaneous preterm birth

OBJECTIVES

To determine the risk of spontaneous preterm birth (sPTB) associated with the length of second stage of labour in the first term delivery.

DESIGN

Retrospective cohort study.

SETTING

University hospital.

POPULATION

Women with first two consecutive singleton births and the first birth at term. Those who did not reach the second stage of labour in the first delivery were excluded.

METHODS

Charts from 2007 to 2019 were reviewed.

MAIN OUTCOME MEASURES

Rate of sPTB (<37 weeks of gestation) in the second delivery.

RESULTS

Of 13 958 women who met study inclusion criteria, 1464 (10.5%) parturients had a prolonged second stage (≥180 min) in their first term delivery. The rate of sPTB in the second delivery was similar in those with and without a prolonged second stage in first delivery (2.8% versus 2.8%; adjusted odds ratio [aOR] 1.35, 95% CI 0.96-1.90). After adjustment for mode of delivery, prolonged second stage was also not associated with subsequent sPTB in those who delivered by spontaneous and operative vaginal delivery. Those delivered by second-stage caesarean section in the first delivery had a higher risk of sPTB in the second delivery (25/526, 4.8%; aOR 2.66, 95% CI 1.71-4.12; p < 0.001), with a more pronounced risk in those with second-stage caesarean following a prolonged second stage of labour (15/259, 5.8%; aOR 3.40, 95% CI 1.94-5.94; p < 0.001).

CONCLUSION

Second-stage duration in a first term vaginal delivery is not associated with subsequent sPTB. The risk of sPTB is increased following second-stage caesarean section, particularly if performed after a prolonged second stage.

Changes in the Frequency of Cesarean Delivery in Nulliparous Women in Labor in a Canadian Population, 1992-2018

OBJECTIVE

To examine the relative contribution of changes in patient demographics and physician management to changes in the cesarean delivery rate in labor among nulliparous women.

METHODS

We conducted a retrospective cohort study of 485,451 births to nulliparous women who experienced labor at or beyond 35 weeks of gestation in Alberta, Canada, from 1992 to 2018. The data were from a province-wide perinatal database. The primary outcome was cesarean delivery. Multivariate logistic regression and calculation of population attributable risk for identified risk factors were performed.

RESULTS

The cesarean delivery rate increased from 12.5% in 1992 to 24% in 2018. The prevalence of maternal risk factors for cesarean delivery such as obesity, maternal age 35 years or older at delivery, and comorbidities increased over the study period. However, this did not account for the increase in cesarean delivery, because the frequency of cesarean delivery increased irrespective of risk status. Additionally, the population-attributable risk for each risk factor was stable across the study period. For example, for maternal age 35 years or older at delivery, the number of cesarean deliveries attributable to this factor (the population-attributable risk) was 0.9 per 100 deliveries in 1992-1998 and 1 per 100 in 2014-2018. The proportion of cesarean deliveries in which nonreassuring fetal status was the indication increased from 30.1% in 1992 to 51.1% in 2018. The absolute rate of cesarean delivery in the second stage of labor increased from 3.1% in 1992 to 5.9% in 2018. This was due to a significant increase, among those who entered the second stage, in cesarean delivery without a trial of forceps, from 2.5% in 1992 to 7.0% in 2018.

CONCLUSION

The observed doubling of the rate of cesarean delivery in labor in first-time mothers was not driven by patient risk factors. Increases in the rate of cesarean delivery for nonreassuring fetal status and decreased operative vaginal deliveries were important factors.

Cervical cerclage in twin pregnancies: An updated systematic review and meta-analysis

OBJECTIVE

Data on the prevention of preterm birth in twin pregnancies with cervical cerclage remain inconsistent. Thus, this study aimed to comprehensively evaluate the value of cervical cerclage as a treatment strategy to prevent preterm birth in twin pregnancies with regard to both maternal and neonatal outcomes.

STUDY DESIGN

In this systematic review and meta-analysis, the PubMed, Cochrane Library, Medline, EMBASE, and Web of Science databases were searched for relevant studies and trials from their inception up to December 2020. Outcomes were expressed as risk ratios and standardized mean differences in a meta-analysis model using STATA 15.0 software.

RESULTS

The search included 944 studies, 15 of which were eligible for inclusion, representing 726 patients treated with cervical cerclage and 8578 non-cerclage treatment controls. When the cervical length was <15 mm, the risk ratio of preterm birth at <37 weeks (0.77, p = 0.01), <34 weeks (0.58, p = 0.002), and <32 weeks (0.61, p = 0.024) of gestation in the cerclage group was significantly lower than that in the non-cerclage group.

CONCLUSION

For twin pregnancies with a cervical length <15 mm, cervical cerclage was associated with significant reduction in preterm birth.

Does the length of second stage of labour or second stage caesarean section in nulliparous women increase the risk of preterm birth in subsequent pregnancies?

OBJECTIVES

This study aimed to investigate the role of prolonged second stage of labour and second stage caesarean section on the risk of spontaneous preterm birth (sPTB) in a subsequent pregnancy.

METHODS

This was a retrospective cohort study of nulliparous women with two consecutive singleton deliveries between 2014 and 2017 at a tertiary centre. In the vaginal delivery cohort, subsequent pregnancy outcomes for women with a prolonged second stage (>2 h) were compared with those with a normal second stage (≤2 h). In the caesarean delivery cohort, women with a first stage or a second stage were compared with the vaginal delivery cohort. The primary outcome was subsequent sPTB.

RESULTS

A total of 821 women met inclusion criteria, of which 74.8% (614/821) delivered vaginally and 25.2% (207/821) delivered by caesarean section. There was no association between a prolonged second stage in the index pregnancy and subsequent sPTB (aOR 0.70, 95% CI 0.13-3.83, p=0.7). The risk of subsequent sPTB was threefold for those with a second stage caesarean section; however this did not reach statistical significance.

CONCLUSIONS

A prolonged second stage of labour in the index pregnancy is not associated with an increased risk of subsequent sPTB. A second stage caesarean section in the index pregnancy may be associated with an increased risk of subsequent sPTB, however there was no statistically significant difference. These findings are important for counseling and suggest that the effects of these factors are not clinically significant to justify additional interventions in the subsequent pregnancy.

Defining arrest in the first and second stages of labor

Normal labor is identified as regular uterine contractions in addition to dilation and effacement of the cervix. It is necessary to define normal labor in order to delineate when a woman's labor pattern diverges from that observed in most women. Labor irregularities are subdivided into protraction disorders and arrest disorders. Identifying abnormal labor patterns and initiating appropriate interventions is essential because prolonged labor is associated with an increase in perinatal morbidity. The aim of this review was to delineate both normal labor progress and also discuss the current evidence-based diagnosis and treatment of protraction and arrest disorders. Many subtleties go into defining the boundaries of the first and second stages of labor. Historically, the Friedman curve established normal limits; but currently Zhang has advanced these definitions by accounting for current demographical characteristics and practice environments. The most significant variables for defining normal progress of labor are parity and regional anesthesia status. The most common causes of labor abnormalities are uterine inactivity, obesity, cephalopelvic disproportion and fetal malposition. Risks of extending the first and/or second stage of labor include postpartum hemorrhage, intraamniotic infection and potentially an increase in neonatal adverse outcomes. The management of labor disorders consists of oxytocin administration, amniotomy, intrauterine pressure catheter use and shared decision-making regarding proceeding with expectant management, operative vaginal delivery or cesarean delivery after weighing the risks and benefits of each option. The decision to extend the duration of labor is personalized for each mother-baby dyad and should be agreed upon depending on individual maternal and fetal circumstances.

Risks associated with cesarean delivery during prolonged second stage of labor

BACKGROUND

Data regarding maternal and fetal morbidities are limited to surgical morbidity per each additional hour in the second stage of labor.

OBJECTIVE

This study aimed to quantify perinatal morbidities associated with cesarean delivery by duration of the second stage of labor.

STUDY DESIGN

Our work is a retrospective cohort study of cesarean deliveries during the second stage of labor using the Consortium on Safe Labor database. All term, singleton pregnancies in cephalic presentation were included. Women with stillbirth or contraindications to vaginal delivery were excluded. Groups were divided by duration of the second stage of labor: ≤3 hours, 3-4 hours, 4-5 hours, 5-6 hours, and >6 hours. The primary outcome was a composite of maternal morbidities. The secondary outcomes were a composite of neonatal morbidities and individual maternal and neonatal morbidities. Baseline demographic and clinical characteristics were compared among groups. Univariate and multivariate analyses were performed.

RESULTS

We included 6273 women in total. In addition, 3652 women (58.2%) went through the second stage for ≤3 hours, 854 (13.6%) for 3 to 4 hours, 618 (9.9%) for 4 to 5 hours, 397 (6.3%) for 5 to 6 hours, and 752 (12.0%) for >6 hours. Neither the maternal nor neonatal morbidity composite outcomes were statistically different among the groups. Extended maternal length of stay (>5 days), increased birthweight, and lower rates of general anesthesia were associated with an increased duration of the second stage of labor. Chorioamnionitis, wound complications, postpartum hemorrhage, and thrombosis did not increase over time.

CONCLUSION

Women should be counseled regarding the duration of the second stage of labor, which should include a discussion of the risks associated with a cesarean delivery with a prolonged second stage of labor. However, these risks may not be as high as anticipated.

Maternal characteristics and neonatal outcomes of emergency repeat caesarean deliveries due to early-term spontaneous labour onset

BACKGROUND

The optimal timing of elective repeat caesarean delivery has yet to be determined. One of the reasons to schedule an elective repeat caesarean delivery before 39 weeks gestation is to avoid emergency caesarean delivery due to spontaneous onset of labour.

AIMS

By ascertaining maternal characteristics and neonatal outcomes associated with early-term onset of spontaneous labour, we aim to determine the optimal timing for each individual repeat caesarean delivery.

MATERIALS AND METHODS

We performed a retrospective analysis of women with repeat caesarean deliveries planned at 38 weeks gestation between 2005 and 2019 at a tertiary referral hospital in Japan. A multivariate logistic regression analysis was adopted to identify independent contributing factors for early-term spontaneous labour onset. We also compared the rate of neonatal adverse events between women who underwent emergency repeat caesarean deliveries due to the onset of early-term labour and the ones who underwent elective repeat caesarean deliveries at 38 weeks.

RESULTS

We included 1152 women. History of vaginal deliveries (adjusted odds ratio (AOR), 2.12; 95% confidence interval (95% CI), 1.21-3.74), history of preterm deliveries (AOR, 2.28; 95% CI, 1.38-3.77), and inadequate maternal weight gain during pregnancy (AOR, 1.78; 95% CI, 1.15-2.75) significantly increased the risk of early-term spontaneous labour onset. In terms of occurrence rate of neonatal complications, we found no significant difference between the groups.

CONCLUSION

These maternal factors are significant predictors for early-term labour onset of repeat caesarean deliveries. The onset of early-term labour did not increase the likelihood of neonatal complications.

Risk of preterm birth after prior term cesarean

Objective

To determine the risk of overall preterm birth (PTB) and spontaneous PTB in a pregnancy after a caesarean section (CS) at term.

Design

Longitudinal linked national cohort study.

Setting

The Dutch Perinatal Registry (1999–2009).

Population

268 495 women with two subsequent singleton pregnancies were identified.

Methods

A cohort study based on linked registered data from two subsequent pregnancies in the Netherlands.

Main outcome measures

The incidence of overall PTB and spontaneous PTB with subgroup analysis on gestational age at first delivery and type of CS (planned or unplanned).

Results

Of 268 495 women with a singleton first pregnancy who delivered at term, 15.76% (n = 42 328) had a CS. The incidence of PTB in the second pregnancy was 2.79% (n = 1182) in women with a previous CS versus 2.46% (n = 5570) in women with a previous vaginal delivery (adjusted odds ratio [aOR] 1.14, 95% confidence interval [CI] 1.07–1.21). This increased risk is mainly driven by an increased risk of spontaneous PTB after previous CS at term (aOR 1.50, 95% CI 1.38–1.70). Analysis for type of CS compared with vaginal delivery showed an aOR on spontaneous PTB of 1.86 (95% CI 1.58–2.18) for planned CS and an aOR of 1.40 (95% CI 1.24–1.58) for unplanned CS.

Conclusions

CS at term is associated with a marginally increased risk of spontaneous PTB in a subsequent pregnancy.

Tweetable abstract

Caesarean section at term is associated with a marginally increased risk of spontaneous PTB in a subsequent pregnancy.

Caesarean section at term is associated with a marginally increased risk of spontaneous PTB in a subsequent pregnancy.

Prolonged second stage of labor and risk of subsequent spontaneous preterm birth

BACKGROUND

Preterm birth is the leading cause of neonatal morbidity and death in the United States. Although many risk factors for spontaneous preterm birth have been elucidated, some women with a previous term delivery experience spontaneous preterm birth in the absence of any identifiable risk factors. Cervical trauma during a prolonged second stage of labor has been postulated as a potential contributor to subsequent spontaneous preterm birth.

OBJECTIVE

This study was designed to examine the relationship between the length of the second stage of labor in the first pregnancy and the risk of spontaneous preterm birth in the subsequent pregnancy.

STUDY DESIGN

This was a retrospective cohort study of all women with 2 consecutive singleton deliveries at a single institution between July 2012 and June 2018, with the first delivery occurring ≥37 weeks of gestation. Multiparous women and those women who did not reach the second stage of labor in the first pregnancy were excluded. Prolonged second stage of labor was defined as ≥4 hours, based on the 75th percentile for this cohort and on recommendations from the National Institute of Child Health and Human Development. Very prolonged second stage of labor was defined as ≥7 hours, based on the 95th percentile for this cohort. The primary outcome was spontaneous preterm birth <37 weeks of gestation in the subsequent pregnancy. The Kruskal-Wallis test compared median values for nonparametric continuous variables; Fisher's exact tests compared proportions for categoric variables, and logistic regression generated odds ratios.

RESULTS

A total of 1032 women met criteria for study inclusion, with an overall subsequent spontaneous preterm birth rate of 3.1%. Prolonged second stage of labor of ≥4 hours was identified in 24.4% (252/1032 women) of the cohort, with 70.6% (178/252 women) of this group delivering vaginally. There was no statistically significant difference in rate of spontaneous preterm birth in those with and without prolonged second stage of labor (4.4% [11/252 women] with prolonged labor vs 2.7% [21/780 women] without prolonged labor; P=.21; odds ratio, 1.6; 95% confidence interval, 0.8-3.5). Very prolonged second stage of labor of ≥7 hours was identified in 4.3% (44/1032 women) of the cohort, with 45.4% (20/44 women) of this group delivering vaginally. There was a significantly higher rate of spontaneous preterm birth in those with very prolonged second stage of labor compared with those without prolonged labor (9.1% [4/44 women] with prolonged labor vs 2.8% [28/988 women] without prolonged labor; P=.04; odds ratio, 3.4; 95% confidence interval, 1.1-10.2), although this finding did not persist after we controlled for the mode of first delivery (adjusted odds ratio, 1.55; 95% confidence interval, 0.65-3.73). Spontaneous preterm birth after very prolonged second stage of labor was identified in only 4 patients, all of whom had a cesarean delivery with the first pregnancy.

CONCLUSION

A second stage of labor of ≥4 hours in the first pregnancy was not associated with an increased risk of subsequent spontaneous preterm birth and was associated with a high rate (>70%) of vaginal birth. A second stage of labor of ≥7 hours did not appear to be associated with an increased risk of preterm birth, when we adjusted for mode of first delivery. There was a nonsignificant increase in the risk of preterm birth in those who delivered via cesarean section after a second stage of labor of ≥7 hours.

Prediction of spontaneous vaginal delivery in nulliparous women with a prolonged second stage of labor: the value of intrapartum ultrasound

BACKGROUND

A limited number of studies have addressed the role of intrapartum ultrasound in the prediction of the mode of delivery in women with prolonged second stage of labor.

OBJECTIVE

The objective of the study was to evaluate the role of transabdominal and transperineal sonographic findings in the prediction of spontaneous vaginal delivery among nulliparous women with prolonged second stage of labor.

STUDY DESIGN

This was a 2-center prospective study conducted at 2 tertiary maternity units. Nulliparous women with a prolonged active second stage of labor, as defined by active pushing lasting more than 120 minutes, were eligible for inclusion. Transabdominal ultrasound to evaluate the fetal head position and transperineal ultrasound for the measurement of the midline angle, the head-perineum distance, and the head-symphysis distance were performed in between uterine contractions and maternal pushes. At transperineal ultrasound the angle of progression was measured at rest and at the peak of maternal pushing effort. The delta angle of progression was defined as the difference between the angle of progression measured during active pushing at the peak of maternal effort and the angle of progression at rest. The sonographic findings of women who had spontaneous vaginal delivery vs those who required obstetric intervention, either vacuum extraction or cesarean delivery, were evaluated and compared.

RESULTS

Overall, 109 were women included. Spontaneous vaginal delivery and obstetric intervention were recorded in 40 (36.7%) and 69 (63.3%) patients, respectively. Spontaneous vaginal delivery was associated with a higher rate of occiput anterior position (90% vs 53.2%, P < .0001), lower head-perineum distance and head-symphysis distance (33.2 ± 7.8 mm vs 40.1 ± 9.5 mm, P = .001, and 13.1 ± 4.6 mm vs 19.5 ± 8.4 mm, P < .001, respectively), narrower midline angle (29.6° ± 15.3° vs 54.2° ± 23.6°, P < .001) and wider angle of progression at the acme of the pushing effort (153.3° ± 19.8° vs 141.8° ± 25.7°, P = .02) and delta-angle of progression (17.3° ± 12.9° vs 12.5° ± 11.0°, P = .04). At logistic regression analysis, only the midline angle and the head-symphysis distance proved to be independent predictors of spontaneous vaginal delivery. More specifically, the area under the curve for the prediction of spontaneous vaginal delivery was 0.80, 95% confidence interval (0.69-0.92), P < .001, and 0.74, 95% confidence interval (0.65-0.83), P = .002, for the midline angle and for the head-symphysis distance, respectively.

CONCLUSION

Transabdominal and transperineal intrapartum ultrasound parameters can predict the likelihood of spontaneous vaginal delivery in nulliparous women with prolonged second stage of labor.

Term cesarean delivery in the first pregnancy is not associated with an increased risk for preterm delivery in the subsequent pregnancy

BACKGROUND

Prior studies have reported an increased risk for preterm delivery following a term cesarean delivery. However, these studies did not adjust for high-risk conditions related to the first cesarean delivery and are known to recur.

OBJECTIVE

The objective of the study was to determine whether there is an association between term cesarean delivery in the first pregnancy and subsequent spontaneous or indicated preterm delivery.

STUDY DESIGN

This was a retrospective cohort study of women with the first 2 consecutive singleton deliveries (2007-2014) identified through a linked pregnancy database at a single institution. Women with a first pregnancy that resulted in cesarean delivery at term were compared with women whose first pregnancy resulted in a vaginal delivery at term. Exclusion criteria were known to recur medical or obstetrical complications during the first pregnancy. A propensity score analysis was performed by matching women who underwent a cesarean delivery with those who underwent a vaginal delivery in the first pregnancy. The association between cesarean delivery in the first pregnancy and preterm delivery in the second pregnancy in this matched set was examined using conditional logistic regression. The primary outcome was overall preterm delivery <37 weeks in the second pregnancy. Secondary outcomes included type of preterm delivery (spontaneous vs indicated), late preterm delivery (34-36 6/7 weeks), early preterm delivery (<34 weeks), and small-for-gestational-age birth.

RESULTS

Of a total of 6456 linked pregnancies, 2284 deliveries were matched; 1142 were preceded by cesarean delivery and 1142 were preceded by vaginal delivery. The main indications for cesarean delivery in the first pregnancy were dystocia in 703 (61.5%), nonreassuring fetal status in 222 (19.4%), breech presentation in 100 (8.8%), and other in 84 (7.4%). The mean (SD) gestational ages at delivery for the second pregnancy was 38.8 (1.8) and 38.9 (1.7) weeks, respectively, for prior cesarean delivery and vaginal delivery. The risks of preterm delivery in the second pregnancy among women with a previous cesarean and vaginal delivery were 6.0% and 5.2%, respectively (adjusted odds ratio, 1.46, 95% confidence interval, [CI] 0.77-2.76). In an analysis stratified by the type of preterm delivery in the second pregnancy, no associations were seen between cesarean delivery in the first pregnancy and spontaneous preterm delivery (4.6% vs 3.9%; adjusted odds ratio, 1.40, 95% confidence interval, 0.59-3.32) or indicated preterm delivery (1.6% vs 1.4%; adjusted odds ratio, 1.21, 95% confidence interval, 0.60-2.46). Similarly, no significant differences were found in late preterm delivery (4.6% vs 4.1%; adjusted odds ratio, 1.13, 95% confidence interval, 0.55-2.29), early preterm delivery (1.6% vs 1.2%; adjusted odds ratio, 1.25, 95% confidence interval, 0.59-2.67), or neonates with birthweight less than the fifth percentile for gestational age (3.6% vs 2.2%; adjusted odds ratio, 1.26, 95% confidence interval, 0.52-3.06).

CONCLUSION

After robust adjustment for confounders through a propensity score analysis related to the indication for the first cesarean delivery at term, cesarean delivery is not associated with an increase in preterm delivery, spontaneous or indicated, in the subsequent pregnancy.

Length of the second stage of labor and preterm delivery risk in the subsequent pregnancy

BACKGROUND

Cervical injury is regarded as an important risk factor for preterm delivery. A prolonged second stage of labor may increase the risk of cervical injury that, in turn, may be associated with increased risk of spontaneous preterm delivery in the subsequent pregnancy.

OBJECTIVE

We sought to evaluate whether the duration of the second stage of labor in a term primiparous singleton delivery is associated with an increased risk of singleton spontaneous preterm delivery (<37 weeks) in the second pregnancy.

STUDY DESIGN

We carried out a retrospective cohort analysis of women with 2 consecutive pregnancies: a first term (≥37 weeks) delivery and second birth. Data were derived from a single institution's prospectively collected obstetrical database from January 2005 through January 2015. Duration of the second stage of labor was examined as a continuous variable, modeled based on nonparametric restricted cubic regression spline with 4 degrees of freedom. Second-stage duration was also examined as short (<30 minutes), normal (30-179 minutes), and prolonged, defined as ≥180 minutes. The association between the duration of the second stage of labor in the first term pregnancy and the risk for spontaneous preterm delivery in the second pregnancy was evaluated before and after adjusting for potential confounders based on the Cox proportional hazards regression model. Associations were expressed based on the adjusted hazard ratio and 95% confidence interval.

RESULTS

In all, 6715 women met inclusion criteria. The hazard of spontaneous preterm delivery in the second pregnancy trended higher with both shorter and longer second-stage labors. The length of the second stage of labor in the first term delivery was categorized as short (<30 minutes) in 1749 (26.0%), normal (30-179 minutes) in 4551 (67.8%), and prolonged (≥180 minutes), in 415 (6.2%) women. Of these 6715 women with a first term delivery, 4.2% (n = 279) delivered spontaneously preterm in the second pregnancy. The risks of spontaneous preterm delivery among women with prolonged (≥180 minutes) second stage of labor and normal labor duration (30-179 minutes) were 5.4% (n = 22) and 3.5% (n = 158), respectively (adjusted hazard ratio, 1.81; 95% confidence interval, 1.15-2.84). This increased risk for prolonged second stage of labor was primarily seen among women who underwent a cesarean (hazard ratio, 3.38; 95% confidence interval, 1.09-10.49), but was imprecise among women who delivered vaginally (hazard ratio, 1.52; 95% confidence interval, 0.62-3.74). The risk of spontaneous preterm delivery among women with short second stage of labor (<30 minutes) in their first term pregnancy was 5.8% (n = 99; hazard ratio, 1.28; 95% confidence interval, 0.99-1.67).

CONCLUSION

The risk of spontaneous preterm delivery in the second pregnancy was increased in women with a prolonged (≥180 minutes) second stage in the first term pregnancy. This risk was even greater among women who were delivered by cesarean in the first pregnancy.

Cesarean delivery in the second stage of labor and the risk of subsequent premature birth

BACKGROUND

Cesarean delivery is being increasingly used by obstetricians for indicated deliveries in the second stage of labor. Unplanned extension of the uterine incision involving the cervix often occurs with these surgeries. Therefore, we hypothesized that cesarean delivery in the second stage of labor may increase the rate of subsequent spontaneous premature birth.

OBJECTIVE

We sought to determine if cesarean delivery in the late first stage of labor or in the second stage of labor increases the risk of a subsequent spontaneous preterm birth.

STUDY DESIGN

We conducted a retrospective cohort study of matched first and second births from a large Canadian perinatal database. The primary outcomes were spontaneous premature birth <37 and <32 weeks of gestation in the second birth. The exposure was stage of labor and cervical dilation at the time of the first cesarean delivery. The protocol and analysis plan was registered prior to obtaining data at Open Science Foundation.

RESULTS

In total, 189,021 paired first and second births were identified. The risk of spontaneous preterm delivery <37 and <32 weeks of gestation in the second birth was increased when the first birth was by cesarean delivery in the second stage of labor (relative risk, 1.57; 95% confidence interval, 1.43-1.73 and relative risk, 2.12; 95% confidence interval, 1.67-2.68, respectively). The risk of perinatal death in the second birth, excluding congenital anomalies, was also correspondingly increased (relative risk, 1.44; 95% confidence interval, 1.05-1.96).

CONCLUSION

Cesarean delivery in second stage of labor was associated with a 2-fold increase in the risk of spontaneous preterm birth <32 weeks of gestation in a subsequent birth. This information may inform management of operative delivery in the second stage.