Risk of preterm birth in the subsequent pregnancy following caesarean section at full cervical dilatation compared with mid‐cavity instrumental delivery

The association between unintended hysterotomy extensions with cesarean delivery and subsequent preterm birth

BACKGROUND

An increased risk for preterm birth has been observed among individuals with a previous second stage cesarean delivery when compared with those with a previous vaginal delivery. One mechanism that may contribute to the increased risk for preterm birth following a second stage cesarean delivery is the increased risk for cervical injury because of extension of the uterine incision (hysterotomy) into the cervix. The contribution of hysterotomy extension to the rate of preterm birth in a subsequent pregnancy has not been investigated and may shed light on the mechanism underlying the observed relationship between the mode of delivery and subsequent preterm birth.

OBJECTIVE

We aimed to quantify the association between unintended hysterotomy extension and preterm birth in a subsequent delivery.

STUDY DESIGN

We performed a retrospective cohort study using electronic perinatal data collected from 2 university-affiliated obstetrical centers. The study included patients with a primary cesarean delivery of a term, singleton live birth and a subsequent singleton birth in the same catchment (2005-2021). The primary outcome was subsequent preterm birth <37 weeks' gestation; secondary outcomes included subsequent preterm birth at <34, <32, and <28 weeks' gestation. We assessed crude and adjusted associations between unintended hysterotomy extensions and subsequent preterm birth with log binomial regression models using rate ratios and 95% confidence intervals. Adjusted models included several characteristics of the primary cesarean delivery such as maternal age, length of active labor, indication for cesarean delivery, chorioamnionitis, and maternal comorbidity.

RESULTS

A total 4797 patients met the study inclusion criteria. The overall rate of unintended hysterotomy extension in the primary cesarean delivery was 6.0% and the total rate of preterm birth in the subsequent pregnancy was 4.8%. Patients with an unintended hysterotomy extension were more likely to have a longer duration of active labor, chorioamnionitis, failed vacuum delivery attempt, second stage cesarean delivery, and persistent occiput posterior position of the fetal head in the primary cesarean delivery and higher rates of smoking in the subsequent pregnancy. Multivariable analyses that controlled for several confounders showed that a history of hysterotomy extension was not associated with a higher risk for preterm birth <37 weeks' gestation (adjusted rate ratio, 1.55; 95% confidence interval, 0.98-2.47), but it was associated with preterm birth <34 weeks' gestation (adjusted rate ratio, 2.49; 95% confidence interval, 1.06-5.42).

CONCLUSION

Patients with a uterine incision extension have a 2.5 times higher rate of preterm birth <34 weeks' gestation when compared with patients who did not have this injury. This association was not observed for preterm birth <37 weeks' gestation. Future research should aim to replicate our analyses with incorporation of additional data to minimize the potential for residual confounding.

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.

Prediction of spontaneous preterm birth in women with previous full dilatation cesarean delivery

BACKGROUND

A previous term (≥37 weeks' gestation), full-dilatation cesarean delivery is associated with an increased risk for a subsequent spontaneous preterm birth. The mechanism is unknown. We hypothesized that the cesarean delivery scar characteristics and scar position relative to the internal cervical os may compromise cervical function, thereby leading to shortening of the cervical length and spontaneous preterm birth.

OBJECTIVE

This study aimed to determine the relationship of cesarean delivery scar characteristics and position, assessed by transvaginal ultrasound, in pregnant women with previous full-dilatation cesarean delivery with the risk of shortening cervical length and spontaneous preterm birth.

STUDY DESIGN

This was a single-center, prospective cohort study of singleton pregnant women (14 to 24 weeks' gestation) with a previous term full-dilatation cesarean delivery who attended a high-risk preterm birth surveillance clinic (2017-2021). Women underwent transvaginal ultrasound assessment of cervical length, cesarean delivery scar distance relative to the internal cervical os, and scar niche parameters using a reproducible transvaginal ultrasound technique. Spontaneous preterm birth prophylactic interventions (vaginal cervical cerclage or vaginal progesterone) were offered for short cervical length (≤25 mm) and to women with a history of spontaneous preterm birth or late miscarriage after full-dilatation cesarean delivery. The primary outcome was spontaneous preterm birth; secondary outcomes included short cervical length and a need for prophylactic interventions. A multivariable logistic regression analysis was used to develop multiparameter models that combined cesarean delivery scar parameters, cervical length, history of full-dilatation cesarean delivery, and maternal characteristics. The predictive performance of models was examined using the area under the receiver operating characteristics curve and the detection rate at various fixed false positive rates. The optimal cutoff for cesarean delivery scar distance to best predict a short cervical length and spontaneous preterm birth was analyzed.

RESULTS

Cesarean delivery scars were visualized in 90.5% (220/243) of the included women. The spontaneous preterm birth rate was 4.1% (10/243), and 12.8% (31/243) of women developed a short cervical length. A history- (n=4) or ultrasound-indicated (n=19) cervical cerclage was performed in 23 of 243 (9.5%) women; among those, 2 (8.7%) spontaneously delivered prematurely. A multiparameter model based on absolute scar distance from the internal os best predicted spontaneous preterm birth (area under the receiver operating characteristics curve, 0.73; 95% confidence interval, 0.57-0.89; detection rate of 60% for a fixed 25% false positive rate). Models based on the relative anatomic position of the cesarean delivery scar to the internal os and the cesarean delivery scar position with niche parameters (length, depth, and width) best predicted the development of a short cervical length (area under the receiver operating characteristics curve, 0.79 [95% confidence interval, 0.71-0.87]; and 0.81 [95% confidence interval, 0.73-0.89], respectively; detection rate of 73% at a fixed 25% false positive rate). Spontaneous preterm birth was significantly more likely when the cesarean delivery scar was <5.0 mm above or below the internal os (adjusted odds ratio, 6.87; 95% confidence interval, 1.34-58; P =.035).

CONCLUSION

In pregnancies following a full-dilatation cesarean delivery, cesarean delivery scar characteristics and distance from the internal os identified women who were at risk for spontaneous preterm birth and developing short cervical length. Overall, the spontaneous preterm birth rate was low, but it was significantly increased among women with a scar located <5.0 mm above or below the internal cervical os. Shortening of cervical length was strongly associated with a low scar position. Our novel findings indicate that a low cesarean delivery scar can compromise the functional integrity of the internal cervical os, leading to cervical shortening and/or spontaneous preterm birth. Assessment of the cesarean delivery scar characteristics and position seem to have use in preterm birth clinical surveillance among women with a previous, full-dilatation cesarean delivery and could better identify women who would benefit from prophylactic interventions.

Mode of birth in subsequent pregnancy when first birth was vacuum extraction or second stage cesarean section at a tertiary referral hospital in Uganda

INTRODUCTION

The trends of increasing use of cesarean section (CS) with a decrease in assisted vaginal birth (vacuum extraction or forceps) is a major concern in health care systems all over the world, particularly in low-resource settings. Studies show that a first birth by CS is associated with an increased risk of repeat CS in subsequent births. In addition, CS compared to assisted vaginal birth (AVB), attracts higher health service costs. Resource-constrained countries have low rates of AVB compared to high-income countries. The aim of this study was to compare mode of birth in the subsequent pregnancy among women who previously gave birth by vacuum extraction or second stage CS in their first pregnancy at Mulago National Referral Hospital, Uganda.

METHODS

This was a retrospective cohort study that involved interviews of 81 mothers who had a vacuum extraction or second stage CS in their first pregnancy at Mulago hospital between November 2014 to July 2015. Mode of birth in the subsequent pregnancy was compared using Chi-2 square test and a Fisher's exact test with a 0.05 level of statistical significance.

RESULTS

Higher rates of vaginal birth were achieved among women who had a vacuum extraction (78.4%) compared to those who had a second stage CS in their first pregnancy (38.6%), p < 0.001.

CONCLUSIONS AND RECOMMENDATIONS

Vacuum extraction increases a woman's chance of having a subsequent spontaneous vaginal birth compared to second stage CS. Health professionals need to continue to offer choice of vacuum extraction in the second stage of labor among laboring women that fulfill its indication. This will help curb the up-surging rates of CS.

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.

Emergency caesareans are associated with an increased risk of recurrent early preterm birth: a commentary

This article includes Author Insights, a video abstract available at: https://vimeo.com/733549553.

Cesarean section in the second stage of labor is associated with early-term and late preterm birth in subsequent pregnancies

OBJECTIVES

The objectives of this study were to determine in a population-based cohort study the association between cesarean section (CS) during the second stage of labor and the risk for preterm birth and/or cervical insufficiency in the subsequent pregnancy; to identify maternal and neonatal risk factors for long-term complications following CS due to prolonged second stage of labor.

METHODS

We conducted a retrospective population-based cohort study including women who had at least one consecutive delivery following a CS at our institution from 1991 to 2018, provided that the first delivery was at term. We divided the study cohort into two groups: (1) women who delivered by CS due to failure to progress during the first stage of labor (n = 1068); and (2) those who delivered by CS due to arrest of descent at the second stage of labor (n = 603).

RESULTS

Of the 120,147 women who met the inclusion criteria, 78,407 had a subsequent delivery during the study period. Women of group 1 were significantly older than those of group 2 (p = .018), and had a higher rate of assisted reproductive technology [61 (5.7%) vs. 18 (3.1%), p < .022,]. Additionally, their hospitalization period was significantly longer (p < .001). The rate of preterm birth in the subsequent delivery was higher among women who had a CS due to arrest of descent than those who had a CS due to arrest in dilatation [43 (7.3%) vs 49 (4.6%), p < .026]. This was confirmed after adjusting for confounding factors In a multivariable regression analysis (OR 1.78, 95% CI 1.14-2.76, p value = .011) A Cox regression analysis implying gestational age at delivery at the time factor identifies CS due to arrest of descent as a risk factor for subsequent preterm birth (Hazard ratio 1.19 95% CI 1.07-1.31).

CONCLUSION

CS due to arrest of descent is an independent risk factor for subsequent preterm birth. The exact mechanisms contributing to this association are yet to be determined.

SYNOPSIS

Cesarean section during the second stage of labor is an independent risk factor for late preterm birth in the subsequent pregnancy when compared to cesarean section in the first stage of labor.

Risk of Preterm Birth among Secundiparas with a Previous Cesarean due to a Failed Vacuum Delivery

BACKGROUND

Studies have found an association between second-stage cesarean sections (SSCSs) and subsequent preterm birth (PTB). We aimed to evaluate if secundiparas with previous second-stage cesarean sections due to a failed vacuum delivery (SSCS-F-VD) are associated with PTB in the subsequent delivery compared with secundiparas with previous spontaneous vaginal birth (SVB) at term. A secondary aim was to compare this association with secundiparas with a previous SSCS at term.

METHODS

A historical, prospective, longitudinal cohort study was conducted in a large tertiary university hospital between 2006 and 2019. Matched mothers who experienced first and second births at the indexed hospital, excluding those with a previous miscarriage or multiple pregnancy in either the first or second birth were grouped based on the mode of delivery and gestational week of the first birth.

RESULTS

Parturients with term SVB and term SSCSs were less likely to experience PTB in the following delivery compared with those who underwent an SSCS-F-VD, with 496/14,551 (3.4%) versus 6/160 (3.8%) versus 5/61 (8.2%), respectively, at p < 0.001. A logistic regression model revealed that secundiparas with previous SSCS-F-VD had an association with PTB in the following delivery compared with term SVB, with an OR of 2.756 (1.097; 6.922, p = 0.031).

CONCLUSION

Previous SSCS-F-VD is associated with PTB in the following delivery, offering valuable insights for pregnancy management and patient counseling.

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.

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.

Prospective Evaluation of the Ultrasound Signs Proposed for the Description of Uterine Niche in Nonpregnant Women

OBJECTIVES

To evaluate the new ultrasound-based signs for the diagnosis of post-cesarean section uterine niche in nonpregnant women.

METHODS

We investigated prospectively a cohort of 160 consecutive women with one previous term cesarean delivery (CD) between December 2019 and 2020. All women were separated into two subgroups according to different stages of labor at the time of their CD: subgroup A (n = 109; 68.1%) for elective CD and CD performed in latent labor at a cervical dilatation (≤4 cm) and subgroup B (n = 51; 31.9%); for CD performed during the active stage of labor (>4 cm).

RESULTS

Overall, the incidence of a uterine niche was significantly (P < .001) higher in women who had an elective (20/45; 44.4%) compared with those who had an emergent (21/115; 18.3%) CD. Compared with subgroup B, subgroup A presented with a significantly (P = .012) higher incidence of uterine niche located above the vesicovaginal fold and with a significantly (P = .0002) lower proportion of cesarean scar positioned below the vesicovaginal fold. There was a significantly (P < .001) higher proportion of women with a residual myometrial thickness (RMT) > 3 mm in subgroup A than in subgroup B and a significant negative relationship was found between the RMT and the cervical dilatation at CD (r = -0.22; P = .008).

CONCLUSIONS

Sonographic cesarean section scar assessment indicates that the type of CD and the stage of labor at which the hysterotomy is performed have an impact on the location of the scar and the scarification process including the niche formation and RMT.

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.

Prior term delivery increases risk of subsequent recurrent preterm birth: An unexpected finding

Background

Women with a prior pregnancy at term are generally considered to be at reduced risk for subsequent spontaneous preterm birth (sPTB), whereas a previous sPTB is a major predictor for a future sPTB.

Aims

The objective of this study was to investigate the risk of recurrent sPTB in women with a prior term birth and a subsequent sPTB.

Materials and Methods

This is a retrospective cohort study conducted at St Thomas’ Hospital in London, UK. There were 430 women included: 230 with a term birth (caesarean section or vaginal delivery) preceding a sPTB (term + sPTB group) and 200 with a prior sPTB only (sPTB only group). The primary outcome was sPTB, <37 weeks gestation.

Results

Of the term + sPTB group, 38.7% (89/230) had a recurrent sPTB compared to 20% (40/200) in the sPTB only group (P < 0.0001), with a relative risk (RR) of 1.9. Of women who had a term caesarean section and a subsequent PTB, 50% (30/60) had a further sPTB (RR 2.5 compared to the sPTB only group), while 34.7% (59/170) of women who had a term vaginal birth and subsequent sPTB, had a further sPTB (RR 1.7 compared to the sPTB only group).

Conclusion

In women who have had a previous sPTB, the risk of a recurrence is much higher than in women with a prior term birth. The aetiology of PTB may be different in this subgroup of women and needs to be further elucidated to determine 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.

CRAFT (Cerclage after full dilatation caesarean section): protocol of a mixed methods study investigating the role of previous in-labour caesarean section in preterm birth risk

BACKGROUND

Full dilatation caesarean sections are associated with recurrent early spontaneous preterm birth and late miscarriage. The risk following first stage caesarean sections, are less well defined, but appears to be increased in late-first stage of labour. The mechanism for this increased risk of late miscarriage and early spontaneous preterm birth in these women is unknown and there are uncertainties with regards to clinical management. Current predictive models of preterm birth (based on transvaginal ultrasound and quantitative fetal fibronectin) have not been validated in these women and it is unknown whether the threshold to define a short cervix (≤25 mm) is reliable in predicting the risk of preterm birth. In addition the efficacy of standard treatments or whether benefit may be derived from prophylactic interventions such as a cervical cerclage is unknown.

METHODS

There are three distinct components to the CRAFT project (CRAFT-OBS, CRAFT-RCT and CRAFT-IMG).

CRAFT-OBS

Observational Study; To evaluate subsequent pregnancy risk of preterm birth in women with a prior caesarean section in established labour. This prospective study of cervical length and quantitative fetal fibronectin data will establish a predictive model of preterm birth.

CRAFT-RCT

Randomised controlled trial arm; To assess treatment for short cervix in women at high risk of preterm birth following a fully dilated caesarean section.

CRAFT-IMG

Imaging sub-study; To evaluate the use of MRI and transvaginal ultrasound imaging of micro and macrostructural cervical features which may predispose to preterm birth in women with a previous fully dilated caesarean section, such as scar position and niche.

DISCUSSION

The CRAFT project will quantify the risk of preterm birth or late miscarriage in women with previous in-labour caesarean section, define the best management and shed light on pathological mechanisms so as to improve the care we offer to women and their babies.

TRIAL REGISTRATION

CRAFT was prospectively registered on 25th November 2019 with the ISRCTN registry ( https://doi.org/10.1186/ISRCTN15068651 ).

Is mode of first birth a risk factor for subsequent preterm birth?

BACKGROUND

Previous preterm birth is a strong predictor of subsequent preterm birth, but less is known about the causes of preterm birth following a full-term first pregnancy. Recent research has highlighted previous caesarean section as a potential risk factor.

AIM

To examine the relationship between mode of first birth and the risk of subsequent preterm birth in New South Wales (NSW), Australia.

MATERIALS AND METHODS

A population-based record-linkage study of NSW women who had a live singleton first birth at ≥37 weeks gestation, followed by a singleton second birth between 2005 and 2017. Relative risk (RR) and 95% CI of preterm birth in the subsequent pregnancy was calculated using modified Poisson regression, with mode of first birth as the exposure. Spontaneous preterm birth and preterm prelabour caesarean were secondary outcomes.

RESULTS

Women who had either an intrapartum (RR: 1.26, 95% CI 1.19-1.32) or prelabour caesarean (RR: 1.26, 95% CI 1.18-1.35) first birth had a higher risk of subsequent preterm birth (any birth <37 weeks gestation), than those who birthed vaginally. Women who had a previous instrumental birth (RR: 0.85, 95% CI 0.79-0.91) or prelabour caesarean (RR: 0.74, 95% CI 0.67-0.82) had lower risks of subsequent spontaneous preterm birth. However, prior prelabour caesarean also greatly increased risk of subsequent preterm prelabour caesarean (RR: 5.25, 95% CI 4.65-5.93).

CONCLUSIONS

The mode of first birth has differing effects on the risk of subsequent spontaneous preterm birth and preterm prelabour caesarean. Awareness of the risk of subsequent preterm birth following caesarean section may help inform clinical decisions around mode of first birth.

Prevention of preterm birth: Proactive and reactive clinical practice-are we on the right track?

Preterm birth remains the major cause of death and disability among children under the age of five. In developing countries antenatal preterm birth prevention clinics are set up to provide cervical length surveillance and/or treatment modalities such as cerclage or progesterone for those women with identified risk factors such as previous cervical treatment or preterm birth. However, 85% of women have no risk factors for PTB and currently there is no biomarker to screen women early in pregnancy. Women will present unexpectedly in threatened preterm labour and we have no choice but to adopt a re-active approach to their care by using predication and preparation strategies such as fetal fibronectin, tocolytic therapy and steroids. Despite these strategies approximately 15-20% of these women will give birth preterm before 34 weeks. There is a urgent need to re-design primary, secondary and tertiary prevention strategies for spontaneous preterm labour (sPTL) in singleton pregnancies aimed at identifying and addressing key gaps in clinical practice and research.

The experience and outcomes of a specialised preterm birth clinic in New Zealand

BACKGROUND

A greater understanding of the risk factors for spontaneous preterm birth and the importance of risk stratification to guide interventions has led to the introduction of preterm birth prevention clinics.

AIM

To evaluate the experience and outcomes of the first specialised preterm birth clinic in New Zealand.

MATERIALS AND METHODS

This observational study reviewed pregnancies cared for in a preterm birth clinic from 2013 to 2018. Cases were identified and data collected from a maternity database and electronic medical records. Analysis was by referral type.

RESULTS

A total of 423 cases were included; 309 elective and 22 acute referrals in pregnancy, and 92 consultations outside pregnancy. For those referred electively in pregnancy, 138/309 (44.7%) fulfilled multiple referral criteria, and 57/309 (18.4%) had ≥2 previous spontaneous preterm births or second trimester losses. Excluding five pregnancies with first trimester miscarriage, 77/304 (25.3%) were managed with a history-indicated cerclage (11 placed pre-conception) and 217/304 (71.4%) had cervical surveillance as primary management, of which 133 (61.3%) did not require treatment. The remaining had treatment for a short cervix; 37 (17.0%) received an ultrasound-indicated cerclage only, 21 (9.7%) vaginal progesterone only and 26 (12.0%) both. Five women (1.6%) had a second trimester loss at 13⁺⁰ -19⁺⁶ and 58/297 (19.5%) had a spontaneous preterm birth at 20⁺⁰ -36⁺⁶  weeks. The 'take home baby' rate was 95.4%.

CONCLUSIONS

Pregnancy outcomes were similar to those reported by other preterm birth prevention clinics. The majority of women who received cervical surveillance as primary management were able to avoid additional treatment.