Preterm Birth In Subsequent Pregnancy Research Articles

Hyposecretion of cervical MUC5B is related to preterm birth in pregnant women after cervical excisional surgery.

Excisional surgery for cervical intraepithelial neoplasia is a risk factor for preterm birth in subsequent pregnancies. However, the underlying mechanisms of this association remain unclear. We previously showed that cervical MUC5B, a mucin protein, may be a barrier to ascending pathogens during pregnancy. We thus hypothesized that hyposecretion of cervical MUC5B is associated with preterm birth after cervical excisional surgery. This prospective nested case-control study (Study 1) included pregnant women who had previously undergone cervical excisional surgery across 11 hospitals. We used proteomics to compare cervicovaginal fluid at 18-22weeks of gestation between the preterm and term birth groups. In another case-control analysis (Study 2), we compared MUC5B expression in nonpregnant uterine tissues between 15 women with a history of cervical excisional surgery and 26 women without a history of cervical surgery. The abundance of MUC5B in cervicovaginal fluid was significantly decreased in the preterm birth group (fold change=0.41, p=.035). Among the 480 quantified proteins, MUC5B had the second highest positive correlation with gestational age at delivery in the combined preterm and term groups. The cervicovaginal microbiome composition was not significantly different between the two groups. Cervical length was not correlated with gestational age at delivery (r=0.18, p=.079). Histologically, the MUC5B-positive area in the nonpregnant cervix was significantly decreased in women with a history of cervical excisional surgery (0.85-fold, p=.048). The distribution of MUC5B-positive areas in the cervical tissues of 26 women without a history of cervical excisional surgery differed across individuals. This study suggests that the primary mechanism by which cervical excisional surgery causes preterm birth is the hyposecretion of MUC5B due to loss of the cervical glands.

Care in pregnancy after stillbirth

Pregnancy after stillbirth is associated with increased risk of stillbirth and other adverse pregnancy outcomes including fetal growth restriction, preeclampsia, and preterm birth in subsequent pregnancies. In addition, pregnancy after stillbirth is associated with emotional and psychological challenges for women and their families. This manuscript summarizes information available to guide clinicians for how to manage a pregnancy after stillbirth by appreciating the nature of the increased risk in future pregnancies, and that these are not affected by interpregnancy interval. Qualitative studies have identified clinician behaviors that women find helpful during subsequent pregnancies after loss which can be implemented into practice. The role of peer support and need for professional input from the antenatal period through to after the birth of a live baby is discussed. Finally, areas for research are highlighted to develop care further for this group of women at increased risk of medical and psychological complications.

Subsequent pregnancy outcomes after second trimester miscarriage or termination for medical/fetal reason: A systematic review and meta-analysis of observational studies.

Women with a prior stillbirth or a history of recurrent first trimester miscarriages are at increased risk of adverse pregnancy outcomes. However, little is known about the impact of a second trimester pregnancy loss on subsequent pregnancy outcome. This review investigated if second trimester miscarriage or termination for medical reason or fetal anomaly (TFMR/TOPFA) is associated with future adverse pregnancy outcomes. A systematic review of observational studies was conducted. Eligible studies included women with a history of a second trimester miscarriage or termination for medical reasons and their pregnancy outcomes in the subsequent pregnancy. Where comparative studies were identified, studies which compared subsequent pregnancy outcomes for women with and without a history of second trimester loss or TFMR/TOPFA were included. The primary outcome was livebirth, and secondary outcomes included: miscarriage (first and second trimester), termination of pregnancy, fetal growth restriction, cesarean section, preterm birth, pre-eclampsia, antepartum hemorrhage, stillbirth and neonatal death. Studies were excluded if exposure was nonmedical termination or if related to twins or higher multiple pregnancies. Electronic searches were conducted using the online databases (MEDLINE, Embase, PubMed and The Cochrane Library) and searches were last updated on June 16, 2023. Risk of bias was assessed using the Newcastle-Ottawa scale. Where possible, meta-analysis was undertaken. PROSPERO registration: CRD42023375033. Ten studies were included, reporting on 12 004 subsequent pregnancies after a second trimester pregnancy miscarriage. No studies were found on outcomes after second trimester TFMR/TOPFA. Overall, available data were of "very low quality" using GRADE assessment. Meta-analysis of cohort studies generated estimated outcome frequencies for women with a previous second trimester loss as follows: live birth 81% (95% CI: 64-94), miscarriage 15% (95% CI: 4-30, preterm birth 13% [95% CI: 6-23]).The pooled odds ratio for preterm birth in subsequent pregnancy after second trimester loss in case-control studies was OR 4.52 (95% CI: 3.03-6.74). Very low certainty evidence suggests there may be an increased risk of preterm birth in a subsequent pregnancy after a late miscarriage. However, evidence is limited. Larger, higher quality cohort studies are needed to investigate this potential association.

Mode of delivery in the first pregnancy and the potential risk for preterm birth in subsequent pregnancy

Mode of delivery in the first pregnancy and the potential risk for preterm birth in subsequent pregnancy

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

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. 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. 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. 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. 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.

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.

Second-stage cesarean delivery and preterm birth in subsequent pregnancy: A large multi-institutional cohort study

Objective: To estimate the risk of preterm birth associated with mode of delivery in a previous pregnancy.Patients and Methods: This was a multicenter retrospective cohort study. Women who had two consecutive deliveries in the participating hospitals between January 2012 and January 2022 were included in this study. They were divided into three groups according to the mode of delivery in a previous pregnancy: vaginal birth (group A), cesarean section before the second stage of labor (group B), and second stage cesarean section (group C). Data were extracted from the medical records. The primary outcome was the risk of spontaneous preterm birth in the subsequent pregnancy. The secondary outcomes were the risk of early spontaneous preterm birth (< 34 weeks) and the medically indicated preterm birth in the subsequent pregnancy. The logistic regression was employed to estimate odds and adjust for confounders.Results: 18,253 women were included. Among them, 10,951 women were in group A, 5111 women in group B, and 2191 women in group C. The rates of spontaneous preterm birth in groups A, B, and C were 5.5%, 7.3%, and 15.1%, respectively. The rates of early spontaneous preterm birth in groups A, B, and C were 2.3%, 3.4%, and 8.2%, respectively. When compared with vaginal birth, second-stage cesarean section significantly increased the risk of spontaneous preterm birth (aOR, 3.23; 95% CI, 2.02–5.17; P = 0.003) and early spontaneous preterm birth (aOR, 3.59; 95% CI, 2.01–5.19; P <0.001) in the subsequent pregnancy. The rates of medically indicated preterm birth in groups A, B, and C were 2.3%, 2.8%, and 2.2%, respectively. There was no statistical difference across the three groups.Conclusion: History of cesarean section at full dilation is independently associated with an increased risk of spontaneous preterm birth in the subsequent pregnancy.

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

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

Patterns of recurrent preterm birth in Western Australia: A 36-year state-wide population-based study.

It is known that a previous preterm birth increases the risk of a subsequent preterm birth, but a limited number of studies have examined this beyond two consecutive pregnancies. This study aimed to assess the risk and patterns of (recurrent) preterm birth up to the fourth pregnancy. We used Western Australian routinely linked population health datasets to identify women who had two or more consecutive singleton births (≥20weeks gestation) from 1980 to 2015. A log-binomial model was used to calculate risk ratios (RRs) and 95% confidence interval (CIs) for preterm birth risk in the third and fourth deliveries by the combined outcomes of previous pregnancies. We analysed 255435 women with 651726 births. About 7% of women had a preterm birth in the first delivery, and the rate of continuous preterm birth recurrence was 22.9% (second), 44.9% (third) and 58.5% (fourth) deliveries. The risk of preterm birth at the third delivery was highest for women with two prior indicated preterm births (RR 12.5, 95% CI: 11.3, 13.9) and for those whose first pregnancy was 32-36weeks gestation, and second pregnancy was less than 32weeks gestation (RR 11.8, 95% CI: 10.3, 13.5). There were similar findings for the second and fourth deliveries. Our findings demonstrate that women with any prior preterm birth were at greater risk of preterm birth in subsequent pregnancies compared with women with only term births, and the risk increased with shorter gestational length, and the number of previous preterm deliveries, especially sequential ones.

Cervical ripening with multiple medical or combined induction methods: Risks of subsequent preterm birth in nulliparous women.

To determine the impact of combined medical and medical/mechanical methods for cervical ripening on the risk of preterm birth in subsequent pregnancy, in nulliparous women. A retrospective cohort study of nulliparous women with term singleton gestations induced by single or combined methods at one center who had their subsequent second birth in the same center. Study groups were compared with a control group of nulliparous women not induced. The primary outcome was risk of preterm labor in the second consecutive birth. Secondary outcomes included neonatal and maternal complications. Cohort included 1277 nulliparous women who underwent cervical ripening by single or combined methods. The study group consisted of 942 women induced by one dose of prostaglandin E2 , 248 women induced by combined methods, and 87 women induced by a mechanical method. The control group consisted of 3903 women. Demographic data of the groups were comparable. Rates of spontaneous preterm birth and early spontaneous preterm birth in the subsequent births did not differ between the groups. Cervical ripening with combined methods or multiple medical methods did not increase the rate of subsequent spontaneous preterm births in nulliparous women or change the neonatal and maternal complications rate.

Risk of pregnancy complications in living kidney donors: A systematic review and meta-analysis

Living kidney donation is associated with glomerular hyperfiltration, predisposing for the development of chronic kidney disease. The present meta-analysis aims to gather current evidence and clarify whether kidney donors are at increased risk of future pregnancy complications. Medline, Scopus, Web of Science, CENTRAL and Google Scholar were systematically searched from inception to August 29, 2021. Observational studies comparing the rates of adverse pregnancy outcomes among kidney donors and non-donors were selected. Random-effects models were fitted to provide meta-analysis estimates, while the quality of evidence was appraised with the Grading of Recommendations Assessment, Development and Evaluation approach. Five studies were included, comprising 430 donors and 23,540 non-donors. Living kidney donation was associated with significantly higher risk of preeclampsia (OR: 2.86, 95% CI: 1.62–5.05, moderate quality of evidence), gestational hypertension (OR: 2.53, 95% CI: 1.11–5.74, low quality of evidence) and preterm birth (OR: 1.32, 95% CI: 1.01–1.74, moderate quality of evidence). The anticipated absolute rates of preeclampsia, gestational hypertension and preterm birth were 7.4%, 5.4% and 8.3%, respectively. The risk of gestational diabetes, cesarean delivery, low birthweight and fetal death was similar between the two groups (low quality of evidence). In conclusion, women with history of kidney donation are at significantly increased risk of preeclampsia, gestational hypertension and preterm birth in subsequent pregnancies, although the absolute rate of complications remains below 10%. Future studies should confirm these effects and improve potential donor counseling by individualizing the risk of adverse perinatal outcomes.

The retrospective study for effectiveness of cervical cerclage in preventing recurrent preterm birth

ObjectiveThis study aimed to clarify the effectiveness of cervical cerclage in preventing recurrent preterm births. Materials and methodsA retrospective study was conducted using the perinatal registration database of the Japan Society of Obstetrics and Gynecology for the Perinatal Center from 2014 to 2016. The efficacies of history-indicated, ultrasound-indicated, and physical examination-indicated cerclage as preventive treatments for women with a history of preterm birth were evaluated by comparing cerclage and non-cerclage cases. Fisher's exact test was performed to evaluate any significant differences in patient backgrounds. Prior to the evaluation, propensity score matching was performed for history-indicated and ultrasound-indicated cerclage patients. ResultsFor this study, 6060 multiparous women with a history of preterm birth were reviewed. After excluding 17 patients with unknown indications for cervical cerclage, 6043 patients were included in the study. History-indicated and ultrasound-indicated cerclage did not reduce the risk of preterm birth in subsequent pregnancies for any of the pregnancy periods (p = 0.413, p = 1.000). In contrast, physical examination-indicated cerclage significantly reduced the risk of subsequent preterm births for all pregnancy periods (p < 0.001). ConclusionSubsequent preterm births were effectively prevented only in physical examination-indicated cerclage cases. For history- or ultrasound-indicated cerclage, statistically significant differences in subsequent preterm births were not evident.

Correlation between cervical excisional procedures and the risk of preterm birth in subsequent pregnancies

Cervical excisional procedures stand as an important risk factor for preterm birth (PTB) in subsequent pregnancies in various articles in the medical literature. We performed an evidence-based review of the obstetrical outcomes succeeding excisional procedures for cervical dysplasia as follows: we reviewed 16 studies published between 2015 and 2020 that assessed whether there is an association between excisional cervical procedures and unfavorable obstetrical outcomes. Nevertheless, there are several other aspects of the problem, taken into account as possibly responsible for increasing the risk of PTB, as the grade of the dysplasia, the effect of depth/length/volume of the excised cone specimen, prophylactic procedures for the prevention of PTB, age, interval conization-pregnancy. The majority of the authors suggested an association between excisional procedures and preterm birth or other obstetrical events. However, some of them did not find statistically significant data in order to strongly affirm a correlation between conization and PTB, or, on the contrary, disproved the given hypothesis. There is no consensus regarding cervical excisions as being an individual risk factor for PTB, therefore more studies need to be conducted in order to come to a strong, universal conclusion.

The Risk of Preterm Birth in Women with Three Consecutive Deliveries—The Effect of Number and Type of Prior Preterm Births

Background: We aimed to explore the association of the number, order, gestational age and type of prior PTB and the risk of preterm birth (PTB) in the third delivery in women who had three consecutive singleton deliveries. Methods: A retrospective cohort study of all women who had three consecutive singleton births at a single medical center over a 20-year period (1994–2013). The primary outcome was PTB (<37 weeks) in the third delivery. Results: 4472 women met inclusion criteria. The rate of PTB in the third delivery was 4.9%. In the adjusted analysis, the risk of PTB was 3.5% in women with no prior PTBs; 10.9% in women with prior one PTB only in the first pregnancy; 16.2% in women with prior one PTB only in the second pregnancy; and 56.5% in women with prior two PTBs. A similar trend was observed when the outcome of interest was spontaneous PTB and when the exposure was limited to prior spontaneous or indicated PTB. Conclusions: In women with a history of PTB, the risk of recurrent PTB in subsequent pregnancies is related to the number and order of prior PTBs. These factors should be taken into account when stratifying the risk of PTB.

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?

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. 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 (>2h) were compared with those with a normal second stage (≤2h). 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. 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. 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.

Sex of the first-born and obstetric complications in the subsequent birth. A study of 2.3 million second births from Denmark, Finland, Norway, and Sweden.

Studies have shown associations between a first-born boy and increased risks of pregnancy loss, stillbirth, decreased birthweight, and preterm birth in subsequent pregnancies, but with limited precision. We examined associations between sex of the first-born and obstetric complications in second births. We calculated the relative risks (RR)s of preeclampsia/eclampsia, placental abruption, stillbirth, and preterm birth in approximately 2.3 million second births comparing women with a preceding first-born boy to those with a first-born girl using the Medical Birth Registries of Denmark, Finland, Norway, and Sweden 1980-2008. In second births following a first-born boy rather than a girl, the RR was 4% higher for preeclampsia/eclampsia (RR=1.04, 95% CI 1.02-1.06), 9% higher for placental abruption (RR=1.09, 95% CI 1.05-1.13), 9% higher for stillbirth (RR=1.09, 95% CI 1.04-1.14), and 8% higher for preterm birth (RR=1.08, 95% CI 1.07-1.09). The population attributable risks ranged from 2% to 4.5%. Male sex of the first-born is associated with small increases in risks of obstetric complications in the second birth. Exploration of the underlying mechanisms is needed to increase our knowledge and treatment options for these serious obstetric complications.

Subsequent pregnancy outcomes following second trimester miscarriage—A prospective cohort study

Objectives: Pregnancy after second-trimester miscarriage represents as clinical challenge. This study sought to determine the rates of recurrence, preterm birth and live births in a cohort of 185 women with previous second-trimester miscarriage. We hypothesized that there would be a higher rate of second-trimester miscarriage and preterm birth in subsequent pregnancy after second trimester miscarriage. The primary objectives of this study were to establish rates of second-trimester miscarriage, preterm birth and live births in this cohort. Secondary objectives were to examine medical and surgical interventions, in addition to other pregnancy outcomes and complications.Study design: This was a prospective cohort study carried out in a tertiary referral center in southern Ireland with over 8000 deliveries per year. 175 women were followed up. Inclusion criteria were an ultrasound confirmed second-trimester miscarriage between June 2009 and June 2013 and subsequently having a pregnancy between July 2009 and January 2016. Fifty-five women did not become pregnant during the study period and were excluded. Ten women were excluded for missing data.Results: Between July 2009 and January 2016, 110 women became pregnant following a previous second-trimester miscarriage. In total, 81 babies were born to 77 mothers. The recurrence rate of second-trimester miscarriage was 6.3% (7/110) and the preterm birth rate was also 6.3% (7/110). The cesarean section rate was 45%. Including those who experienced first or second trimester miscarriage, 47% (78/155) of those who were followed up did not go on to have a live infant.Conclusions: Women experiencing second-trimester miscarriage are at increased risk in subsequent pregnancies of recurrence. Second-trimester miscarriage needs to be highlighted as a risk factor for adverse pregnancy outcomes. Greater research into its pathophysiology is required to advance preventative measures.

Women with threatened preterm labour followed by term delivery have an increased risk of spontaneous preterm birth in subsequent pregnancies: a population-based cohort study.

To evaluate the association of a history of threatened preterm labour (TPL) followed by term delivery with the risk of spontaneous preterm delivery (PTD) in subsequent pregnancy. Population-based cohort study. Data of the National Health Insurance Claims Database and a national health-screening programme for infants and children in South Korea. Women who had their first singleton delivery in 2010 and a subsequent second singleton delivery between 2011 and 2015. Multivariable analysis adjusting for maternal age and interval between first and second deliveries was used to assess the risk of PTD based on PTD, TPL followed by term delivery, and term delivery in the first pregnancy. The risk of PTD during the second pregnancy. This study included 115629 women with two consecutive deliveries during the study period. Spontaneous PTD rates in the second pregnancy were 7.71, 2.22 and 1.02% in women with PTD, TPL followed by term delivery, and term delivery in the first pregnancy, respectively. Threatened preterm labour followed by term delivery in the first pregnancy was associated with increased risk of PTD in the subsequent pregnancy after adjustment for potential confounding factors (adjusted odds ratio 2.21; 95% CI 1.76-2.78). Although women with a history of TPL followed byterm delivery had a lower risk of PTD during a subsequentpregnancy compared with those with history of previous PTD, they still had a significantly increased risk ofPTD compared with those who delivered at term without TPL. The history of threatened preterm labour followed by term delivery is related to increased risk of subsequent spontaneous preterm delivery.

Mode of delivery and preterm birth in subsequent births: A systematic review and meta-analysis.

Preterm birth continues to be an important problem in modern obstetrics and a large public health concern and is related to increased risk for neonatal morbidity and mortality. The aim of this study was to evaluate the data in the literature to determine the relationships between mode of delivery (cesarean section and vaginal birth) in the first pregnancy and the risk of subsequent preterm birth from a multi-year population based cohorts (PROSPERO registration number: 42018090788). Five electronic databases were searched. Observational studies that provided mode of delivery and subsequent preterm birth were eligible. Ten cohort studies, involving 10333501 women, were included in this study. Compared with vaginal delivery, women delivering by previous cesarean section had a significantly higher risk of preterm birth in subsequent births (RR 1.10, 95%CI 1.01–1.20). After adjusting confounding factors, there was still statistical significance (aRR 1.12, 95%CI 1.01–1.24). However, both before and after adjustment, there was no difference among very preterm birth (RR 1.14, 95%CI 0.90–1.43; aRR 1.16, 95%CI 0.80–1.68; respectively). To the best of our knowledge, this is the first systematic review and meta-analysis that suggests previous cesarean section could increase the risk of preterm birth in subsequent pregnancies. The result could provide policy makers, clinicians, and expectant parents to reduce the occurrence of unnecessary cesarean section.

Previous Adverse Outcome of Term Pregnancy and Risk of Preterm Birth in Subsequent Pregnancy.

Objective Evaluate risk of preterm birth (PTB, < 37 completed weeks' gestation) among a population of women in their second pregnancy with previous full term birth but other adverse pregnancy outcome. Methods The sample included singleton live born infants between 2007 and 2012 in a birth cohort file maintained by the California Office of Statewide Health Planning and Development. The sample was restricted to women with two pregnancies resulting in live born infants and first birth between 39 and 42weeks' gestation. Logistic regression was used to calculate the risk of PTB in the second birth for women with previous adverse pregnancy outcome including: small for gestational age (SGA) infant, preeclampsia, placental abruption, or neonatal death (≤ 28 days). Risks were adjusted for maternal factors recorded for second birth. Results The sample included 133,622 women. Of the women with any previous adverse outcome, 4.7% had a PTB while just 3.0% of the women without a previous adverse outcome delivered early (relative risk adjusted for maternal factors known at delivery 1.4, 95% CI 1.3-1.5). History of an SGA infant, placental abruption, or neonatal death increased the adjusted risk of PTB in their second birth by 1.5-3.7-fold. History of preeclampsia did not elevate the risk of a preterm birth in the subsequent birth. Conclusions for Practice The findings indicate that women with previous SGA infant, placental abruption, or neonatal death, despite a term delivery, may be at increased risk of PTB in the subsequent birth. These women may be appropriate participates for future interventions aimed at reduction in PTB.