Risk Of Subsequent Preterm Birth Research Articles

Cesarean section at full dilatation in the first birth is not associated with an increased risk of subsequent miscarriage: A historical cohort study.

Cesarean section at full dilatation has been associated with an increased risk of subsequent preterm birth. We hypothesized that there may be an increased risk of miscarriage in pregnancies that follow cesarean section at full dilatation. This study aimed to determine if a first-term (≥37 weeks) cesarean section at full dilatation is associated with an increased risk of miscarriage in the next pregnancy. A historical cohort study was conducted using routinely collected hospital data within the Aberdeen Maternity and Neonatal Databank (AMND). The population included were women who had a first-term birth and who had a second birth recorded within the AMND. Logistic and multinomial regression was used to determine any association with miscarriage at any gestation and for early (<13 weeks gestation) and late (13-23 + 6 weeks gestation) miscarriage, with cesarean section at full dilatation defined as the exposure. Miscarriage in the second pregnancy (spontaneous loss of intrauterine pregnancy prior to 24 weeks gestation) was the primary outcome. In total, 33 452 women were included. Women who had a first cesarean section at full dilatation were no more likely to have a miscarriage at any gestation than women with all other modes of first birth (including all vaginal births, planned CS, and the first stage of labor (<10 cm dilated CS)) [adjusted OR 0.84 (0.66-1.08); p = 0.18]. There was no association with early or late miscarriage after a CSfd, though the sample size for late miscarriage was small. This is the first observational study to investigate the risk of miscarriage following first-term CSfd. We found no association between miscarriage at any gestation following a first-term CSfd compared to all other modes of first birth.

Trends and risk of recurrent preterm birth in pregnancy cohorts in rural Bangladesh, 1990–2019

IntroductionA history of preterm birth reportedly increases the risk of subsequent preterm birth. This association has primarily been studied in high-income countries and not in low-income settings in transition with...

History of induced abortion and the risk of preterm birth: a retrospective cohort study

Objectives To explore the relationship between a history of induced abortion and follow-up preterm birth. Methods We performed a retrospective cohort study of 27,176 women aged 19 to 48 years old in the city of Dongguan. Participants were divided into two groups according to the history of induced abortion. We used log-binomial regression to estimate adjusted risk ratios of preterm birth (gestation at less than 37 weeks) and early preterm birth (gestation at less than 34 weeks) for women with a history of induced abortion. Four models adjusted for different baseline data were used to verify the stability of the results. We also performed a subgroup analysis and mediation effect analysis to control for the influence of confounding factors and analyzed the relationship between the number of abortions and subsequent preterm birth. Results Our study included 2,985 women who had undergone a prior induced abortion. Women who reported having a prior induced abortion were more likely to have preterm births before 37 weeks and 34 weeks, with risk ratios of 1.18 (95% CI 1.02–1.36) and 1.65 (95% CI 1.23–2.21), respectively. The above associations were stable in all models. We also found that a history of induced abortion was independently associated with a higher risk of preterm birth and early preterm birth in the subgroups. After controlling for the indirect effect of demographic data, the direct effect of abortion history on follow-up preterm delivery was still significantly different. The higher the number of abortions, the greater the risk of subsequent preterm birth. Conclusions This study suggests that induced abortion increases the risk of subsequent preterm birth.

Vaginal flora during pregnancy and subsequent risk of preterm birth or prelabor rupture of membranes: a nested case–control study from China

BackgroundThe findings of the association of vaginal flora with preterm birth (PTB) or prelabor rupture of membranes (PROM) were conflicts. Moreover, vaginal flora was different by ethnicity and the evidence from China was limited.MethodsThis study was a nested case control study, based on Yiwu birth cohort. We assessed vaginal microbiota in the second or third trimester, using 16S rDNA Amplicon Sequencing and explored the association between the diversity and composition of vaginal flora and PTB or PROM.ResultsWe finally included 144 pregnant women. In present study, the alpha diversity of TPROM (Term prelabor rupture of membranes) samples was lower than that of full term samples (Chao1 index: P < 0.05). When we further categorized PTB (Preterm birth) into SPB (PTB without PROM) and PPROM (Preterm prelabor rupture of membranes), there was no difference between SPB and full term. In addition, we found that the proportion of PCoA2 in TPROM group was different from that in full term group and preterm group. The difference between groups was significant according to anosim analysis (R = 0.059, P < 0.001). With LEfSe (Linear discriminant analysis Effect Size) analysis, we found that the abundance of Lactobacillus in the vaginal flora of pregnant women with preterm birth was the highest (P = 0.003).ConclusionIn Chinese pregnant women, the alpha diversity in TPROM group was significantly lower than that in both PTB and full term group. However, there was no difference between PTB and full term. Lactobacillus was the most abundant in preterm birth group. More studies should be conducted to confirm our findings.

Comparative effectiveness and risk of preterm birth of local treatments for cervical intraepithelial neoplasia and stage IA1 cervical cancer: a systematic review and network meta-analysis.

The trade-off between comparative effectiveness and reproductive morbidity of different treatment methods for cervical intraepithelial neoplasia (CIN) remains unclear. We aimed to determine the risks of treatment failure and preterm birth associated with various treatment techniques. In this systematic review and network meta-analysis, we searched MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials database for randomised and non-randomised studies reporting on oncological or reproductive outcomes after CIN treatments from database inception until March 9, 2022, without language restrictions. We included studies of women with CIN, glandular intraepithelial neoplasia, or stage IA1 cervical cancer treated with excision (cold knife conisation [CKC], laser conisation, and large loop excision of the transformation zone [LLETZ]) or ablation (radical diathermy, laser ablation, cold coagulation, and cryotherapy). We excluded women treated with hysterectomy. The primary outcomes were any treatment failure (defined as any abnormal histology or cytology) and preterm birth (<37 weeks of gestation). The network for preterm birth also included women with untreated CIN (untreated colposcopy group). The main reference group was LLETZ for treatment failure and the untreated colposcopy group for preterm birth. For randomised controlled trials, we extracted group-level summary data, and for observational studies, we extracted relative treatment effect estimates adjusted for potential confounders, when available, and we did random-effects network meta-analyses to obtain odds ratios (ORs) with 95% CIs. We assessed within-study and across-study risk of bias using Cochrane tools. This systematic review is registered with PROSPERO, CRD42018115495 and CRD42018115508. 7880 potential citations were identified for the outcome of treatment failure and 4107 for the outcome of preterm birth. After screening and removal of duplicates, the network for treatment failure included 19 240 participants across 71 studies (25 randomised) and the network for preterm birth included 68 817 participants across 29 studies (two randomised). Compared with LLETZ, risk of treatment failure was reduced for other excisional methods (laser conisation: OR 0·59 [95% CI 0·44-0·79] and CKC: 0·63 [0·50-0·81]) and increased for laser ablation (1·69 [1·27-2·24]) and cryotherapy (1·84 [1·33-2·56]). No differences were found for the comparison of cold coagulation versus LLETZ (1·09 [0·68-1·74]) but direct data were based on two small studies only. Compared with the untreated colposcopy group, risk of preterm birth was increased for all excisional techniques (CKC: 2·27 [1·70-3·02]; laser conisation: 1·77 [1·29-2·43]; and LLETZ: 1·37 [1·16-1·62]), whereas no differences were found for ablative methods (laser ablation: 1·05 [0·78-1·41]; cryotherapy: 1·01 [0·35-2·92]; and cold coagulation: 0·67 [0·02-29·15]). The evidence was based mostly on observational studies with their inherent risks of bias, and the credibility of many comparisons was low. More radical excisional techniques reduce the risk of treatment failure but increase the risk of subsequent preterm birth. Although there is uncertainty, ablative treatments probably do not increase risk of preterm birth, but are associated with higher failure rates than excisional techniques. Although we found LLETZ to have balanced effectiveness and reproductive morbidity, treatment choice should rely on a woman's age, size and location of lesion, and future family planning. National Institute for Health and Care Research: Research for Patient Benefit.

Low Fetal Fraction of Cell Free DNA at Non-Invasive Prenatal Screening Increases the Subsequent Risk of Preterm Birth in Uncomplicated Singleton Pregnancy.

ObjectiveTo examine the association between low fetal fraction (FF) of cell free DNA determined at non-invasive prenatal screening (NIPS) and the subsequent risk of preterm birth in uncomplicated singleton pregnancy.MethodsWe retrospectively interrogated NIPS System and hospitalization records from April 2018 to August 2019 and obtained results from 1521 consecutive and uncomplicated women with singleton pregnancy in which plasma FF of cell free DNA at NIPS had been investigated together with birth outcomes. We examined the association between FF and preterm birth (PTB) by regression analysis.ResultsThe incidence of preterm birth, low birthweight, and macrosomia in the study population was 5.06%, 2.89%, and 7.17%, respectively. FF at NIPS in the second to fourth quartiles (8.40–11.07, 11.08–13.70, and >13.70%, respectively) was associated with higher gestational age at delivery relative to the lowest quartile (<8.40%), with estimated mean increases of 0.27 weeks (95% CI: 0.05–0.49), 0.29 weeks (95% CI: 0.06–0.51), and 0.28 weeks (95% CI: 0.05–0.51), respectively (P for trend = 0.027). Low FF (< the 5th percentile) was associated with an increased risk of PTB (adjusted OR: 2.23, 95% CI: 1.01–4.98, P = 0.047) compared to normal FF (≥ the 5th and ≤ the 95th percentiles). In addition, when compared to women with normal FF and body mass index (BMI) <25 at NIPS, the risk of early PTB (< 34 weeks gestation) was remarkably significantly higher among those with low FF and BMI ≥25 (adjusted OR: 6.29, 95% CI: 1.71–23.15, P = 0.006).ConclusionOur study supports the association of low FF at NIPS with PTB (especially early PTB) for uncomplicated singleton pregnancy.

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

ObjectivesAn 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 designThis 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. ResultsOut 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. ConclusionA 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.

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

ObjectivesEmergency 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. Results54% (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]). ConclusionsIn 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.

The role of confounding in the association between pregnancy complications and subsequent preterm birth: a cohort study.

To estimate the degree of confounding necessary to explain the associations between complications in a first pregnancy and the subsequent risk of preterm birth. Population-based cohort study. Western Australia. Women (n = 125 473) who gave birth to their first and second singleton children between 1998 and 2015. Relative risk (RR) of a subsequent preterm birth (<37 weeks of gestation) with complications of pre-eclampsia, placental abruption, small-for-gestational age and perinatal death (stillbirth and neonatal death within 28 days of birth). We derived e-values to determine the minimum strength of association for an unmeasured confounding factor to explain away an observed association. Complications in a first pregnancy were associated with an increased risk of a subsequent preterm birth. Relative risks were significantly higher when the complication was recurrent, with the exception of first-term perinatal death. The association with subsequent preterm birth was strongest when pre-eclampsia was recurrent. The risk of subsequent preterm birth with pre-eclampsia was 11.87 (95% CI 9.52-14.79) times higher after a first term birth with pre-eclampsia, and 64.04 (95% CI 53.58-76.55) times higher after a preterm first birth with pre-eclampsia, than an uncomplicated term birth. The e-values were 23.22 and 127.58, respectively. The strong associations between recurrent pre-eclampsia, placental abruption and small-for-gestational age with preterm birth supports the hypothesis of shared underlying causes that persist from pregnancy to pregnancy. High e-values suggest that recurrent confounding is unlikely, as any such unmeasured confounding factor would have to be uncharacteristically large. First pregnancy complications are associated with a higher risk of subsequent preterm birth, with evidence strongest for pregnancies complicated by pre-eclampsia.

Gestational age as a predictor for subsequent preterm birth in New South Wales, Australia

BackgroundThere is no validated evidence base on predictive ability and absolute risk of preterm birth by gestational age of the previous pregnancy.MethodsWe conducted a retrospective cohort study of mothers who gave birth to their first two children in New South Wales, 1994–2016 (N = 517,558 mothers). For each week of final gestational age of the first birth, we calculated relative and absolute risks of subsequent preterm birth.ResultsFor mothers whose first birth had a gestational age of 22 to 30 weeks the absolute risks of clinically significant preterm second birth (before 28, 32, and 34 weeks) were all less than 14%. For all gestational ages of the first child the median gestational ages of the second child were all at least 38 weeks. Sensitivity and positive predictive values were all below 30%.ConclusionPrevious gestational age alone is a poor predictor of subsequent risk of preterm birth.

618Is mode of first birth a risk factor for subsequent preterm birth?

Abstract 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 pregnancy. Recent research highlighted previous caesarean as a potential risk factor and we aimed to further explore this risk. Methods This population-based record linkage study included all women in NSW, Australia who had a live singleton first birth at ≥ 37 weeks gestation, followed by a singleton second birth between 2005–2017. Relative risk (RR) and 95%CI of having a subsequent preterm birth, spontaneous preterm birth or preterm pre-labour caesarean was calculated using individual modified Poisson regression models, with mode of first birth as the exposure. Results Women who had 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, than those who birthed vaginally. Those who had a pre-labour caesarean (RR:0.74, 95%CI 0.67–0.82) had a lower risk of subsequent spontaneous preterm birth. However, prior pre-labour caesarean also greatly increased the risk of subsequent preterm prelabour caesarean (RR:5.25, 95%CI 4.65–5.93). Conclusions Pre-labour and intrapartum caesareans have differing effects on the risk of subsequent spontaneous preterm birth and preterm pre-labour caesarean. Key messages The risk of subsequent preterm birth following a first birth caesarean depends on whether the caesarean occurred before or after the onset of labour and whether the subsequent preterm birth is spontaneous or a pre-labour caesarean.

Risk Indicators for Urinary Tract Infections in Low Risk Pregnancy and the Subsequent Risk of Preterm Birth.

Symptomatic urinary tract infections are associated with preterm birth. However, data on risk indicators for urinary tract infections are limited and outdated. The research is a secondary analysis. The study was a prospective multicenter cohort study of low-risk pregnant women. Logistic regression was used to identify risk indicators for urinary tract infections. The incidence of urinary tract infections was 9.4%. Multivariate logistic regression showed that a history of recurrent urinary tract infections and the presence of asymptomatic bacteriuria in the present pregnancy were associated with urinary tract infections (resp. OR 3.14, 95%CI 1.40–7.02 and OR 1.96 95%CI 1.27–3.03). Women with a urinary tract infection were at increased risk of preterm birth compared to women without a urinary tract infection (12 vs. 5.1%; adjusted HR 2.5 95%CI 1.8–3.5). This increased risk was not found in women with the identified risk indicators (resp. 5.3% vs. 5.1%, adjusted HR 0.35 95%CI 0.00–420 and adjusted HR 1.5 95CI% 0.59–3.9). In conclusion, in low-risk pregnant women, risk indicators for urinary tract infections are: a history of recurrent urinary tract infections and the presence of asymptomatic bacteriuria. The risk of preterm birth is increased in women with a urinary tract infection in this pregnancy. However, women with recurrent urinary tract infections and asymptomatic bacteriuria this pregnancy appear not to be at increased risk of preterm birth.

History of IUD utilization and the risk of preterm birth: a cohort study.

To explore whether a history of IUD use could increase the risk of subsequent preterm birth. We performed a cohort study of 24,496 multipara aged 19-48years in Dongguan City. Each subject was followed up for 1 year, and 12,508 women obtained pregnancy outcomes. They were divided into 2 groups: 2130 subjects with IUD use history (exposure group), and 10,378 subjects without IUD use history (control group). The exposure group will remove the IUD before pregnancy. The primary outcomes were preterm birth (less than 37weeks of gestation) and early preterm birth (less than 34weeks of gestation). We used log-binomial regression to estimate adjusted risk ratios (aRR) of preterm birth and early preterm birth for women with a history of IUD. According to the different adjusted baseline data, three regression models were established, and the propensity matching score method was also used to verify the stability of the results. The delivery rate of women with IUD history was 51.24%, and that of women without IUD was 51.03% (2 = 0.063, P = 0.802). Six hundred and eighty-five women had preterm birth (5.48%, 95% CI 5.08-5.88) and 133 women had early preterm birth (1.06%, 95% CI 0.83-1.24). Compared with the control group, the incidence of preterm birth and early preterm birth in the exposure group were significantly lower. The results are stable in all four models. Subgroup analysis also supported the result. This study also found that the longer the women used IUD before pregnancy, the younger the age of first using IUD, and the shorter the time from condom removal to pregnancy, the lower the incidence of premature birth. The women with a history of IUD use are less likely to have premature birth after the IUD is removed. More prospective studies are needed to confirm it.

337 High grade chronic placental inflammation is independently associated with increased risk of recurrent preterm birth

Histologic examination of the placenta is often performed following delivery. Although placental examination cannot change the index pregnancy outcome, it may inform risk assessment for subsequent pregnancy. Prior research has examined the association between individual histologic lesions and pregnancy outcomes. The purpose of this study is to determine the association of combinations of histologic findings and risk of subsequent preterm birth (PTB). This was a retrospective cohort study of deliveries at a tertiary care center from January 2009 to March 2018. Individuals with two births and an index placental pathology report during the study period were included. The presence of maternal vascular malperfusion (MVM), fetal vascular malperfusion (FVM), maternal and/or fetal acute inflammation (AI) and chronic inflammation (CI) was extracted from the pathology report for each index placenta, classified as none, low, or high grade. A logistic model incorporating all four placental components was used to estimate associations between each histologic lesion category and risk of subsequent preterm birth, while controlling for the other lesion categories. Analysis was repeated restricting the sample only to those with an index PTB. 3926 women were included. Among all index pregnancies, presence of high grade CI and low grade MVM were associated with increased odds of subsequent PTB. AI (both low- and high-grade) and low grade FVM were associated with lower odds of subsequent PTB (Table). Among 924 index pregnancies delivering preterm, only high grade CI was independently associated with recurrent PTB (OR 1.57, 95% CI 1.02- 2.41, Figure). High-grade chronic placental inflammation in an index pregnancy is the only pathology independently associated with an increased risk of subsequent PTB, regardless of whether the index delivery is preterm or term. Decreased odds of PTB with AI and FVM in the full sample were not replicated when evaluating recurrent PTB.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Induction of labor with Foley catheter and risk of subsequent preterm birth: follow-up study of two randomized controlled trials (PROBAAT-1 and -2).

ABSTRACTObjectiveTo evaluate the rate of preterm birth (PTB) in a subsequent pregnancy in women who had undergone term induction using a Foley catheter compared with prostaglandins.MethodsThis was a follow‐up study of two large randomized controlled trials (PROBAAT‐1 and PROBAAT‐2). In the original trials, women with a term singleton pregnancy with the fetus in cephalic presentation and with an indication for labor induction were randomized to receive either a 30‐mL Foley catheter or prostaglandins (vaginal prostaglandin E2 in PROBAAT‐1 and oral misoprostol in PROBAAT‐2). Data on subsequent ongoing pregnancies > 16 weeks’ gestation were collected from hospital charts from clinics participating in this follow‐up study. The main outcome measure was preterm birth < 37 weeks’ gestation in a subsequent pregnancy.ResultsFourteen hospitals agreed to participate in this follow‐up study. Of the 1142 eligible women, 572 had been allocated to induction of labor using a Foley catheter and 570 to induction of labor using prostaglandins. Of these, 162 (14%) were lost to follow‐up. In total, 251 and 258 women had a known subsequent pregnancy > 16 weeks' gestation in the Foley catheter and prostaglandin groups, respectively. There were no differences in baseline characteristics between the groups. The overall rate of PTB in a subsequent pregnancy was 9/251 (3.6%) in the Foley catheter group vs 10/258 (3.9%) in the prostaglandin group (relative risk (RR), 0.93; 95% CI, 0.38–2.24), and the rate of spontaneous PTB was 5/251 (2.0%) vs 5/258 (1.9%) (RR, 1.03; 95% CI, 0.30–3.51).ConclusionIn women with term singleton pregnancy, induction of labor using a 30‐mL Foley catheter is not associated with an increased risk of PTB in a subsequent pregnancy, as compared to induction of labor using prostaglandins. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Caesarean birth and risk of subsequent preterm birth: a retrospective cohort study.

To determine the risk of spontaneous and medically indicated preterm birth associated with mode of birth in previous term-born pregnancy. Retrospective cohort study. Two UK maternity units. A total of 16340 women with first two consecutive singleton births and the first birth at term. Retrospective cohort study using routinely collected clinical data. Incidence of spontaneous preterm birth and medically indicated preterm birth at less than 37weeks of gestation after term birth, in relation to mode of birth in first pregnancy. Subgroup analysis on cervical dilatation at the time of first caesarean birth. Compared with vaginal birth, emergency caesarean birth at full dilatation was associated with an increase in spontaneous preterm birth (2.3% vaginal birth versus 4.5% full dilatation caesarean; adjusted odds ratio [aOR] 3.29, 95% CI 2.02-5.13, P<0.001). Elective caesarean, emergency caesarean at <4cm dilatation, and emergency caesarean at 4-9cm dilatation were associated with increased medically indicated preterm birth (0.8% vaginal births versus 1.9% elective caesarean, 3.3% <4cm caesarean, 1.3% 4-9cm caesarean; aOR 2.30, 95% CI 1.19-4.15, P=0.009; aOR 4.68, 95% CI 2.98-7.24, P<0.001; and aOR 2.43, 95% CI 1.43-4.00, P=0.001, respectively). Term caesarean in the first stage of labour or performed prelabour is associated with medically indicated preterm birth. Term caesarean in the second stage of labour is associated with spontaneous preterm birth. Caesarean in the second stage of labour is associated with spontaneous preterm birth.

Term Complications and Subsequent Risk of Preterm Birth: Registry-Based Study

Abstract Objective To explore conditions and outcomes of a first delivery at term that might predict later preterm birth. Design Population based, prospective register based study. Setting Medical Birth Registry of Norway, 1999-2015. Participants 302 192 women giving birth (live or stillbirth) to a second singleton child between 1999 and 2015. Main outcome measures Main outcome was the relative risk of preterm delivery ( Results Women with any of the five complications at term showed a substantially increased risk of preterm delivery in the next pregnancy. The absolute risks for preterm delivery in a second pregnancy were 3.1% with none of the five term complications (8202/265 043), 6.1% after term pre-eclampsia (688/11 225), 7.3% after term placental abruption (41/562), 13.1% after term stillbirth (72/551), 10.0% after term neonatal death (22/219), and 6.7% after term small for gestational age (463/6939). The unadjusted relative risk for preterm birth after term pre-eclampsia was 2.0 (95% confidence interval 1.8 to 2.1), after term placental abruption was 2.3 (1.7 to 3.1), after term stillbirth was 4.2 (3.4 to 5.2), after term neonatal death was 3.2 (2.2 to 4.8), and after term small for gestational age was 2.2 (2.0 to 2.4). On average, the risk of preterm birth was increased 2.0-fold (1.9-fold to 2.1-fold) with one term complication in the first pregnancy, and 3.5-fold (2.9-fold to 4.2-fold) with two or more complications. The associations persisted after excluding recurrence of the specific complication in the second pregnancy. These links between term complications and preterm delivery were also seen in the reverse direction: preterm birth in the first pregnancy predicted complications in second pregnancies delivered at term. Conclusions Pre-eclampsia, placental abruption, stillbirth, neonatal death, or small for gestational age experienced in a first term pregnancy are associated with a substantially increased risk of subsequent preterm delivery. Term complications seem to share important underlying causes with preterm delivery that persist from pregnancy to pregnancy, perhaps related to a mother’s predisposition to disorders of placental function.

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

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. To examine the relationship between mode of first birth and the risk of subsequent preterm birth in New South Wales (NSW), Australia. A population-based record-linkage study of NSW women who had a live singleton first birth at ≥37weeks 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. 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 <37weeks 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). 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.

Term complications and subsequent risk of preterm birth: registry based study

ObjectiveTo explore conditions and outcomes of a first delivery at term that might predict later preterm birth.DesignPopulation based, prospective register based study.SettingMedical Birth Registry of Norway, 1999-2015.Participants302 192 women giving...

OC09.02: The risk of subsequent preterm birth in women with a short cervix who delivered at term

OC09.02: The risk of subsequent preterm birth in women with a short cervix who delivered at term