Predicting risk of spontaneous preterm delivery in women with a singleton pregnancy

Mode of Delivery and Neonatal Outcomes of Preterm Deliveries: A Retrospective Study in Greece

Background and Objectives: Preterm birth is a significant concern in obstetrics and neonatology since preterm neonates are at higher risk of various health complications and may require specialized care. The optimal mode of delivery in preterm birth is a matter of debate. This study aimed to evaluate the mode of delivery in preterm neonates and the associated neonatal outcomes. Material and Methods: This was a retrospective cohort study including all preterm neonates born between January 2010 and December 2020 at the 3rd Department of Obstetrics & Gynecology of Aristotle University of Thessaloniki, Greece. The mode of delivery in relation to gestational age groups and the cause of preterm birth were analyzed. Neonatal outcomes were also evaluated according to gestational age, indication and mode of delivery. Results: A total of 1167 preterm neonates were included in the study; the majority of them were delivered via cesarean section (76.1%). Most of the preterm neonates (n = 715; 61.3%) were delivered at 32+0-36+6 weeks, while cesarean section was the most common mode of delivery after 28+0 weeks. Furthermore, spontaneous onset of labor (OR: 6.038; 95% CI: 3.163-11.527; p < 0.001), multiple gestation (OR: 1.782; 95% CI: 1.165-2.227; p = 0.008) and fetal distress (OR: 5.326; 95% CI: 2.796-10.144; p < 0.001) were the main causes of preterm delivery at 32+0-36+6 weeks. The overall mortality rate was 8.1% among premature neonates. Regarding morbidity, 919 (78.7%) neonates were diagnosed with respiratory disorders, 129 (11.1%) with intraventricular hemorrhage and 30 (2.6%) with necrotizing enterocolitis. Early gestational age at delivery was the main risk factor of neonatal morbidity and mortality. Notably, the mode of delivery did not have any impact on neonatal survival (OR: 1.317; 95% CI: 0.759-2.284; p = 0.328), but preterm neonates born via cesarean section were at higher risk of respiratory disorders, compared to those born via vaginal delivery (OR: 2.208; 95% CI: 1.574-3.097; p < 0.001). Conclusions: Most preterm deliveries occurred in the moderate-to-late preterm period via cesarean section. Early gestational age at delivery was the main prognostic factor of neonatal morbidity and mortality, while the mode of delivery did not have any impact on neonatal survival. Future research on the mode of delivery of the preterm neonates is warranted to establish definitive answers for each particular gestational age.

Cervical microRNA expression and spontaneous preterm birth

BACKGROUND

Preterm birth remains a major public health issue affecting 10% of all pregnancies and increases risks of neonatal morbidity and mortality. Approximately 50% to 60% of preterm births are spontaneous, resulting from preterm premature rupture of membranes or preterm labor. The pathogenesis of spontaneous preterm birth is incompletely understood, and prediction of preterm birth remains elusive. Accurate prediction of preterm birth would reduce infant morbidity and mortality through targeted patient referral to hospitals equipped to care for preterm infants. Two previous studies have analyzed cervical microRNAs in association with spontaneous preterm birth and the length of gestation, but the extent to which microRNAs serve as predictive biomarkers remains unknown.

OBJECTIVE

This study aimed to examine associations between cervical microRNA expression and spontaneous preterm birth, with the specific goal of identifying a subset of microRNAs that predict spontaneous preterm birth.

STUDY DESIGN

We performed a prospective, nested, case-control study of 25 cases with spontaneous preterm birth and 49 term controls. Controls were matched to cases in a 2:1 ratio on the basis of age, parity, and self-identified race. Cervical swabs were collected at a mean gestational age of 17.1 (4.8) weeks of gestation, and microRNAs were analyzed using a quantitative polymerase chain reaction array. Normalized microRNA expression was compared between cases and controls, and a false discovery rate of 0.2 was applied to account for multiple comparisons. Histopathologic analysis of slides of cervical swab samples was performed to quantify leukocyte burden for adjustment in conditional regression models. We explored the use of Relief-based unsupervised identification of top microRNAs and support vector machines to predict spontaneous preterm birth. We performed microRNA enrichment analysis to explore potential biologic targets and pathways in which up-regulated microRNAs might be involved.

RESULTS

Of the 754 microRNAs on the polymerase chain reaction array, 346 were detected in ≥75% of participants' cervical swabs. Average cervical microRNA expression was significantly higher in cases of spontaneous preterm birth than in controls (P=.01). There were 95 significantly up-regulated individual microRNAs (>2-fold change) in cases of subsequent spontaneous preterm birth compared with term controls (P<.05; q<0.2). Notably, miR-143, miR-30e-3p, and miR-199b were all significantly up-regulated, which is consistent with the 1 previous study of cervical microRNA and spontaneous preterm birth. A Relief-based, novel variable (feature) selection machine learning approach had low-to-moderate prediction accuracy, with an area under the receiver operating curve of 0.71. Enrichment analysis revealed that identified microRNAs may modulate inflammatory cell signaling.

CONCLUSION

In this prospective nested case-control study of cervical microRNA expression and spontaneous preterm birth, we identified a global increase in microRNA expression and up-regulation of 95 distinct microRNAs in association with subsequent spontaneous preterm birth. Larger and more diverse studies are required to determine the ability of microRNAs to accurately predict spontaneous preterm birth, and mechanistic work to facilitate development of novel therapeutic interventions to prevent spontaneous preterm birth is warranted.

Dense phenotyping from electronic health records enables machine learning-based prediction of preterm birth

BACKGROUND

Identifying pregnancies at risk for preterm birth, one of the leading causes of worldwide infant mortality, has the potential to improve prenatal care. However, we lack broadly applicable methods to accurately predict preterm birth risk. The dense longitudinal information present in electronic health records (EHRs) is enabling scalable and cost-efficient risk modeling of many diseases, but EHR resources have been largely untapped in the study of pregnancy.

METHODS

Here, we apply machine learning to diverse data from EHRs with 35,282 deliveries to predict singleton preterm birth.

RESULTS

We find that machine learning models based on billing codes alone can predict preterm birth risk at various gestational ages (e.g., ROC-AUC = 0.75, PR-AUC = 0.40 at 28 weeks of gestation) and outperform comparable models trained using known risk factors (e.g., ROC-AUC = 0.65, PR-AUC = 0.25 at 28 weeks). Examining the patterns learned by the model reveals it stratifies deliveries into interpretable groups, including high-risk preterm birth subtypes enriched for distinct comorbidities. Our machine learning approach also predicts preterm birth subtypes (spontaneous vs. indicated), mode of delivery, and recurrent preterm birth. Finally, we demonstrate the portability of our approach by showing that the prediction models maintain their accuracy on a large, independent cohort (5978 deliveries) from a different healthcare system.

CONCLUSIONS

By leveraging rich phenotypic and genetic features derived from EHRs, we suggest that machine learning algorithms have great potential to improve medical care during pregnancy. However, further work is needed before these models can be applied in clinical settings.

Maternal preterm birth prediction in the United States: a case-control database study

Background

Preterm birth is serious public health worldwide, and early prediction of preterm birth in pregnant women may provide assistance for timely intervention and reduction of preterm birth. This study aimed to develop a preterm birth prediction model that is readily available and convenient for clinical application.

Methods

Data used in this case-control study were extracted from the National Vital Statistics System (NVSS) database between 2018 and 2019. Univariate and multivariate logistic regression analyses were utilized to find factors associated with preterm birth. Odds ratio (OR) and 95% confidence interval (CI) were used as effect measures. The area under the curve (AUC), accuracy, sensitivity, and specificity were utilized as model performance evaluation metrics.

Results

Data from 3,006,989 pregnant women in 2019 and 3,039,922 pregnant women in 2018 were used for the model establishment and external validation, respectively. Of these 3,006,989 pregnant women, 324,700 (10.8%) had a preterm birth. Higher education level of pregnant women [bachelor (OR = 0.82; 95%CI, 0.81–0.84); master or above (OR = 0.82; 95%CI, 0.81–0.83)], pre-pregnancy overweight (OR = 0.96; 95%CI, 0.95–0.98) and obesity (OR = 0.94; 95%CI, 0.93–0.96), and prenatal care (OR = 0.48; 95%CI, 0.47–0.50) were associated with a reduced risk of preterm birth, while age ≥ 35 years (OR = 1.27; 95%CI, 1.26–1.29), black race (OR = 1.26; 95%CI, 1.23–1.29), pre-pregnancy underweight (OR = 1.26; 95%CI, 1.22–1.30), pregnancy smoking (OR = 1.27; 95%CI, 1.24–1.30), pre-pregnancy diabetes (OR = 2.08; 95%CI, 1.99–2.16), pre-pregnancy hypertension (OR = 2.22; 95%CI, 2.16–2.29), previous preterm birth (OR = 2.95; 95%CI, 2.88–3.01), and plurality (OR = 12.99; 95%CI, 12.73–13.24) were related to an increased risk of preterm birth. The AUC and accuracy of the prediction model in the testing set were 0.688 (95%CI, 0.686–0.689) and 0.762 (95%CI, 0.762–0.763), respectively. In addition, a nomogram based on information on pregnant women and their spouses was established to predict the risk of preterm birth in pregnant women.

Conclusions

The nomogram for predicting the risk of preterm birth in pregnant women had a good performance and the relevant predictors are readily available clinically, which may provide a simple tool for the prediction of preterm birth.

Society for Maternal-Fetal Medicine Special Statement: Quality metrics for optimal timing of antenatal corticosteroid administration

Preterm birth is a leading cause of perinatal morbidity and mortality. Antenatal corticosteroid administration before preterm birth reduces the risks of perinatal death, respiratory morbidity, necrotizing enterocolitis, and intraventricular hemorrhage and reduces the costs of perinatal care. Antenatal corticosteroids are optimally effective when administered within 7 days before preterm birth. However, only 20% to 40% of early preterm infants receive antenatal corticosteroids within 7 days before birth, in part because it is difficult to predict the precise timing of preterm birth. Until 2020, The Joint Commission had a Perinatal Care quality metric measuring the rate of antenatal corticosteroid administration at any time before early preterm birth. This metric incentivized providers to use antenatal corticosteroids liberally. The Joint Commission retired the metric in 2020 after the rate reached more than 97% in The Joint Commission-accredited hospitals. However, the metric did not evaluate whether the timing of antenatal corticosteroid administration was optimal, that is, within 7 days of birth. A 2016 multistakeholder Cooperative Workshop recommended the development of a new quality metric to assess the rate of optimally timed antenatal corticosteroids among early preterm births. In this statement, we outline proposed specifications for such a metric and discuss potential uses, advantages, limitations, and barriers. Furthermore, we propose a balancing metric that tracks the percentage of patients treated with antenatal corticosteroids who ultimately give birth at term. We suggest that the use of these new metrics may incentivize more conservative antenatal corticosteroid timing, which could, in turn, lead to meaningfully improved outcomes for preterm neonates.

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

BACKGROUND

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.

AIMS

This study aimed to assess the risk and patterns of (recurrent) preterm birth up to the fourth pregnancy.

MATERIALS AND METHODS

We used Western Australian routinely linked population health datasets to identify women who had two or more consecutive singleton births (≥20 weeks 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.

RESULTS

We analysed 255 435 women with 651 726 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 32-36 weeks gestation, and second pregnancy was less than 32 weeks gestation (RR 11.8, 95% CI: 10.3, 13.5). There were similar findings for the second and fourth deliveries.

CONCLUSIONS

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.

PredictPTB: an interpretable preterm birth prediction model using attention-based recurrent neural networks

BACKGROUND

Early identification of pregnant women at risk for preterm birth (PTB), a major cause of infant mortality and morbidity, has a significant potential to improve prenatal care. However, we lack effective predictive models which can accurately forecast PTB and complement these predictions with appropriate interpretations for clinicians. In this work, we introduce a clinical prediction model (PredictPTB) which combines variables (medical codes) readily accessible through electronic health record (EHR) to accurately predict the risk of preterm birth at 1, 3, 6, and 9 months prior to delivery.

METHODS

The architecture of PredictPTB employs recurrent neural networks (RNNs) to model the longitudinal patient's EHR visits and exploits a single code-level attention mechanism to improve the predictive performance, while providing temporal code-level and visit-level explanations for the prediction results. We compare the performance of different combinations of prediction time-points, data modalities, and data windows. We also present a case-study of our model's interpretability illustrating how clinicians can gain some transparency into the predictions.

RESULTS

Leveraging a large cohort of 222,436 deliveries, comprising a total of 27,100 unique clinical concepts, our model was able to predict preterm birth with an ROC-AUC of 0.82, 0.79, 0.78, and PR-AUC of 0.40, 0.31, 0.24, at 1, 3, and 6 months prior to delivery, respectively. Results also confirm that observational data modalities (such as diagnoses) are more predictive for preterm birth than interventional data modalities (e.g., medications and procedures).

CONCLUSIONS

Our results demonstrate that PredictPTB can be utilized to achieve accurate and scalable predictions for preterm birth, complemented by explanations that directly highlight evidence in the patient's EHR timeline.

Pregnancy outcomes in relation to disease activity and anti-rheumatic treatment strategies in women with rheumatoid arthritis

OBJECTIVES

To explore the association of maternal rheumatoid arthritis (RA) to pregnancy outcomes, especially preterm birth (PTB) and small for gestational age (SGA), in relation to disease activity and anti-rheumatic treatment before and during pregnancy.

METHODS

By linking prospective clinical rheumatology registers (CRR) in Sweden (SRQ) and Denmark (DANBIO) with medical birth registers, we identified 1,739 RA-pregnancies and 17 390 control-pregnancies (matched 1:10 on maternal age, birth year, parity) with delivery 2006-2018. Disease activity (DAS28, CRP, HAQ-score) and anti-rheumatic treatment nine months before and during pregnancy were identified through CRR and prescribed drug registers. Using logistic regression, we estimated adjusted odds ratios (aOR) with 95% confidence intervals (CI) for PTB and SGA overall and stratified by disease activity and anti-rheumatic treatment before and during pregnancy, adjusting for maternal characteristics.

RESULTS

We found increased aOR of PTB (1.92, 1.56-2.35) and SGA (1.93, 1.45-2.57) in RA-pregnancies vs control-pregnancies. For RA-pregnancies with DAS28-CRP ≥ 4.1 vs < 3.2 during pregnancy, aOR was 3.38 (1.52-7.55) for PTB and 3.90 (1.46-10.4) for SGA. Use of oral corticosteroids (yes/no) during pregnancy resulted in an aOR of 2.11 (0.94-4.74) for PTB. Corresponding figure for biologics was 1.38 (0.66-2.89). Combination therapy, including biologics before pregnancy, was a marker of increased risk of both PTB and SGA.

CONCLUSION

During pregnancy, disease activity rather than treatment seems to be the most important risk factor for PTB and SGA in RA. Women with RA should be carefully monitored during pregnancy, especially if they have moderate to high disease activity or/and are treated with extensive anti-rheumatic treatment.

Developing and validating multivariable prediction models for predicting the risk of 7-day neonatal readmission following vaginal and cesarean birth using administrative databases

BACKGROUND

Approximately 3.5% of deliveries in Canada result in potentially preventable neonatal readmission, often times due to preventable morbidities. With complexities in hospital discharge planning, health care providers may benefit in identifying infants at risk of readmission for additional monitoring.

OBJECTIVES

To develop and validate models for predicting 7-day neonatal readmission following vaginal or cesarean births.

METHODS

All liveborn term singleton infants without congenital anomalies in the province of Alberta who were not admitted to the NICU were identified using perinatal and hospitalization databases. A temporal split-sample was used for model development (2012-2014, vaginal n = 63,378; cesarean n = 21,225) and external validation (2014-2015, vaginal n = 21,583, cesarean n = 7,477). Multivariable logistic regression models using backward stepwise selection were used to identify predictors of 7-day readmission. We evaluated predictors of maternal age, Apgar score, length-of-stay, birthweight, gestational age, parity, residence, and sex. Hosmer-Lemeshow test and c-statistics were used to estimate calibration and discrimination.

RESULTS

The rate of readmission was 3.3% (95% CI 3.1%, 3.4%) and 2.1% (95% CI 1.9%, 2.3%) following vaginal and cesarean births in the development dataset. Prediction model following vaginal birth, excluding predictors of length-of-stay and birthweight, had sub-optimal performance in development (c-statistics 0.69) and validation data (c-statistics 0.68). Prediction model following cesarean birth, excluding predictors of maternal age, birthweight, and residence, had sub-optimal performance in development (c-statistics 0.62) and validation data (c-statistics 0.64). Readmission was observed in 7.9% (95% CI 7.1%, 8.8%) and 4.9% (95% CI 3.9%, 6.1%) of infants of vaginal and cesarean births, respectively, in the top quintile for the risk of 7-day readmission.

CONCLUSION

Using routinely collected administrative data, we developed and validated prediction models for neonatal readmission following vaginal and cesarean births. Presently the model is sub-optimal for use in risk assessment and planning at discharge, however, additional information may improve the predictive performance.

Second-trimester transvaginal ultrasound measurement of cervical length for prediction of preterm birth: a blinded prospective multicentre diagnostic accuracy study

Objective

To estimate the diagnostic performance of sonographic cervical length for the prediction of preterm birth (PTB).

Design

Prospective observational multicentre study.

Setting

Seven Swedish ultrasound centres.

Sample

A cohort of 11 456 asymptomatic women with a singleton pregnancy.

Methods

Cervical length was measured with transvaginal ultrasound at 18–20 weeks of gestation (C×1) and at 21–23 weeks of gestation (C×2, optional). Staff and participants were blinded to results.

Main outcome measures

Area under receiver operating characteristic curve (AUC), sensitivity, specificity, positive and negative predictive values (PPV and NPV), positive and negative likelihood ratios (LR+ and LR−), number of false‐positive results per true‐positive result (FP/TP), number needed to screen to detect one PTB (NNS) and prevalence of ‘short’ cervix.

Results

Spontaneous PTB (sPTB) at <33 weeks of gestation occurred in 56/11 072 (0.5%) women in the C×1 population (89% white) and in 26/6288 (0.4%) in the C×2 population (92% white). The discriminative ability of shortest endocervical length was better the earlier the sPTB occurred and was better at C×2 than at C×1 (AUC to predict sPTB at <33 weeks of gestation 0.76 versus 0.65, difference in AUC 0.11, 95% CI 0.01–0.23). At C×2, the shortest endocervical length of ≤25 mm (prevalence 4.4%) predicted sPTB at <33 weeks of gestation with sensitivity 38.5% (10/26), specificity 95.8% (5998/6262), PPV 3.6% (10/274), NPV 99.7% (5988/6014), LR+ 9.1, LR− 0.64, FP/TP 26 and NNS 629.

Conclusions

Second‐trimester sonographic cervical length can identify women at high risk of sPTB. In a population of mainly white women with a low prevalence of sPTB its diagnostic performance is at best moderate.

Tweetable abstract

Cervical length screening to predict preterm birth in a white low‐risk population has moderate performance.

Cervical length screening to predict preterm birth in a white low‐risk population has moderate performance.

Uterine distention as a factor in birth timing: retrospective nationwide cohort study in Sweden

OBJECTIVES

To determine whether uterine distention is associated with human pregnancy duration in a non-invasive observational setting.

DESIGN

Retrospective cohort study modelling uterine distention by interaction between maternal height and uterine load.

SETTING

The study is based on the 1990-2013 population data from all delivery units in Sweden.

PARTICIPANTS

Uncomplicated first pregnancies of healthy Nordic-born mothers with spontaneous onset of labour. Pregnancies were classified as twin (n=2846) or singleton (n=527 868). Singleton pregnancies were further classified as carrying a large for gestational age fetus (LGA, n=24 286) or small for gestational age fetus (SGA, n=33 780).

OUTCOME MEASURES

Statistical interaction between maternal height and uterine load categories (twin vs singleton pregnancies, and LGA vs SGA singleton pregnancies), where the outcome is pregnancy duration.

RESULTS

In all models, statistically significant interaction was found. Mothers carrying twins had 2.9 times larger positive linear effect of maternal height on gestational age than mothers carrying singletons (interaction p=5e-14). Similarly, the effect of maternal height was strongly modulated by the fetal growth rate in singleton pregnancies: the effect size of maternal height on gestational age in LGA pregnancies was 2.1 times larger than that in SGA pregnancies (interaction p<1e-11). Preterm birth OR was 1.4 when the mother was short, and 2.8 when the fetus was extremely large for its gestational age; however, when both risk factors were present together, the OR for preterm birth was larger than expected, 10.2 (interaction p<0.0005).

CONCLUSIONS

Across all classes, maternal height was significantly associated with child's gestational age at birth. Interestingly, in short-statured women with large uterine load (twins, LGA), spontaneous delivery occurred much earlier than expected. The interaction between maternal height, uterine load size and gestational age at birth strongly suggests the effect of uterine distention imposed by fetal growth on birth timing.

Predictions of Preterm Birth from Early Pregnancy Characteristics: Born in Guangzhou Cohort Study

Preterm birth (PTB, <37 weeks) is the leading cause of death in children <5 years of age. Early risk prediction for PTB would enable early monitoring and intervention. However, such prediction models have been rarely reported, especially in low- and middle-income areas. We used data on a number of easily accessible predictors during early pregnancy from 9044 women in Born in Guangzhou Cohort Study, China to generate prediction models for overall PTB and spontaneous, iatrogenic, late (34–36 weeks), and early (<34 weeks) PTB. Models were constructed using the Cox proportional hazard model, and their performance was evaluated by Harrell’s c and D statistics and calibration plot. We further performed a systematic review to identify published models and validated them in our population. Our new prediction models had moderate discrimination, with Harrell’s c statistics ranging from 0.60–0.66 for overall and subtypes of PTB. Significant predictors included maternal age, height, history of preterm delivery, amount of vaginal bleeding, folic acid intake before pregnancy, and passive smoking during pregnancy. Calibration plots showed good fit for all models except for early PTB. We validated three published models, all of which were from studies conducted in high-income countries; the area under receiver operating characteristic for these models ranged from 0.50 to 0.56. Based on early pregnancy characteristics, our models have moderate predictive ability for PTB. Future studies should consider inclusion of laboratory markers for the prediction of PTB.

Fathers Count: The Impact of Paternal Risk Factors on Birth Outcomes

Objective To determine the contribution of paternal factors to the risk of adverse birth outcomes. Methods This is a retrospective cross-sectional analysis using birth certificate data from 2004 to 2015 retrieved from the Finger Lakes Regional Perinatal Data System. Primiparous women with singleton pregnancies were analyzed in the study. Two multivariate logistic regression models were conducted to assess potential paternal risk factors including age, race/ethnicity, and education on four birth outcomes, including preterm birth (PTB), low birthweight (LBW), high birthweight (HBW), and small for gestational age (SGA). Results A total of 36,731 singleton births were included in the analysis. Less paternal education was significantly related to an elevated risk of PTB, LBW, and SGA, even after adjustment for maternal demographic, medical, and lifestyle factors (P < 0.05). Paternal race/ethnicity was also significantly associated with all four birth outcomes (P < 0.05) while controlling for maternal factors. Older paternal age was associated with increased odds (OR 1.012, 95% CI 1.003-1.022) of LBW. Maternal race/ethnicity partially mediated the association of paternal race/ethnicity with HBW and SGA. Maternal education partially mediated the relationship between paternal education and SGA. Conclusion Paternal factors were important predictors of adverse birth outcomes. Our results support the inclusion of fathers in future studies and clinical programs aimed at reducing adverse birth outcomes.

Accuracy of a combined insulin-like growth factor-binding protein-1/interleukin-6 test (Premaquick) in predicting delivery in women with threatened preterm labor

PURPOSE

To determine values of combinations of interleukin-6 (IL-6)/cervical native insulin-like growth factor-binding protein-1 (IGFBP-1)/total IGFBP-1 (Premaquick©) in predicting spontaneous deliveries and spontaneous exclusive preterm deliveries in women with threatened preterm labor.

METHODS

Women with singleton pregnancies between gestation age (GA) of 24 weeks and 36 weeks and 6 days with preterm labor were recruited during a prospective multicenter study. Premaquick© was positive when at least two of three biomarkers were positive. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were estimated for both prediction of spontaneous deliveries and spontaneous exclusive preterm deliveries.

RESULTS

Ninety-seven (99.0%) out of 98 women enrolled were analyzed. Based on delivery status 7/14 days post-enrollment of general study population, Premaquick© had a sensitivity of 87.1/85.7%, a specificity of 92.4/96.8%, a PPV of 84.4/93.8% and a NPV of 93.9/92.3% for prediction of spontaneous delivery. Predictive accuracy of Premaquick© test in relation to days of enrollment were: 90.7% (≤7 days) and 92.8% (≤14 days). For women enrolled at GA <35 weeks, Premaquick© had a sensitivity of 100.0/87.5%, a specificity of 94.1/96.9%, a PPV of 70.5/87.5%, a NPV of 100.0/96.9% and an accuracy of 95.0/95.0% for prediction of preterm delivery within 7/14 days of enrollment, respectively. PPV was most significantly different in both groups when outcomes were compared between 2 days and 14 days post-enrollment (P<0.001).

CONCLUSION

This novel triple biomarker model of native and total IGFBP-1 and IL-6 appears to be an accurate test in predicting spontaneous deliveries and spontaneous exclusive preterm deliveries in threatened preterm labor in singleton pregnancies.

The transformative potential of an integrative approach to pregnancy

BACKGROUND

Complex traits typically involve diverse biological pathways and are shaped by numerous genetic and environmental factors. Pregnancy-associated traits and pathologies are further complicated by extensive communication across multiple tissues in two individuals, interactions between two genomes-maternal and fetal-that obscure causal variants and lead to genetic conflict, and rapid evolution of pregnancy-associated traits across mammals and in the human lineage. Given the multi-faceted complexity of human pregnancy, integrative approaches that synthesize diverse data types and analyses harbor tremendous promise to identify the genetic architecture and environmental influences underlying pregnancy-associated traits and pathologies.

METHODS

We review current research that addresses the extreme complexities of traits and pathologies associated with human pregnancy.

RESULTS

We find that successful efforts to address the many complexities of pregnancy-associated traits and pathologies often harness the power of many and diverse types of data, including genome-wide association studies, evolutionary analyses, multi-tissue transcriptomic profiles, and environmental conditions.

CONCLUSION

We propose that understanding of pregnancy and its pathologies will be accelerated by computational platforms that provide easy access to integrated data and analyses. By simplifying the integration of diverse data, such platforms will provide a comprehensive synthesis that transcends many of the inherent challenges present in studies of pregnancy.

Applying Precision Public Health to Prevent Preterm Birth

Preterm birth (PTB) is one of the major health-care challenges of our time. Being born too early is associated with major risks to the child with potential for serious consequences in terms of life-long disability and health-care costs. Discovering how to prevent PTB needs to be one of our greatest priorities. Recent advances have provided hope that a percentage of cases known to be related to risk factors may be amenable to prevention; but the majority of cases remain of unknown cause, and there is little chance of prevention. Applying the principle of precision public health may offer opportunities previously unavailable. Presented in this article are ideas that may improve our abilities in the fields of studying the effects of migration and of populations in transition, public health programs, tobacco control, routine measurement of length of the cervix in mid-pregnancy by ultrasound imaging, prevention of non-medically indicated late PTB, identification of pregnant women for whom treatment of vaginal infection may be of benefit, and screening by genetics and other “omics.” Opening new research in these fields, and viewing these clinical problems through a prism of precision public health, may produce benefits that will affect the lives of large numbers of people.

Different insulin types and regimens for pregnant women with pre-existing diabetes

BACKGROUND

Insulin requirements may change during pregnancy, and the optimal treatment for pre-existing diabetes is unclear. There are several insulin regimens (e.g. via syringe, pen) and types of insulin (e.g. fast-acting insulin, human insulin).

OBJECTIVES

To assess the effects of different insulin types and different insulin regimens in pregnant women with pre-existing type 1 or type 2 diabetes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 October 2016), ClinicalTrials.gov (17 October 2016), the WHO International Clinical Trials Registry Platform (ICTRP; 17 October 2016), and the reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared different insulin types and regimens in pregnant women with pre-existing diabetes.We had planned to include cluster-RCTs, but none were identified. We excluded quasi-randomised controlled trials and cross-over trials. We included studies published in abstract form and contacted the authors for further details when applicable. Conference abstracts were superseded by full publications.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, conducted data extraction, assessed risk of bias, and checked for accuracy. We assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

The findings in this review were based on very low-quality evidence, from single, small sample sized trial estimates, with wide confidence intervals (CI), some of which crossed the line of no effect; many of the prespecified outcomes were not reported. Therefore, they should be interpreted with caution. We included five trials that included 554 women and babies (four open-label, multi-centre, two-arm trials; one single centre, four-arm RCT). All five trials were at a high or unclear risk of bias due to lack of blinding, unclear methods of randomisation, and selective reporting of outcomes. Pooling of data from the trials was not possible, as each trial looked at a different comparison.1. One trial (N = 33 women) compared Lispro insulin with regular insulin and provided very low-quality evidence for the outcomes. There were seven episodes of pre-eclampsia in the Lispro group and nine in the regular insulin group, with no clear difference between the two groups (risk ratio (RR) 0.68, 95% CI 0.35 to 1.30). There were five caesarean sections in the Lispro group and nine in the regular insulin group, with no clear difference between the two groups (RR 0.59, 95% CI 0.25 to 1.39). There were no cases of fetal anomaly in the Lispro group and one in the regular insulin group, with no clear difference between the groups (RR 0.35, 95% CI 0.02 to 8.08). Macrosomia, perinatal deaths, episodes of birth trauma including shoulder dystocia, nerve palsy, and fracture, and the composite outcome measure of neonatal morbidity were not reported.2. One trial (N = 42 women) compared human insulin to animal insulin, and provided very low-quality evidence for the outcomes. There were no cases of macrosomia in the human insulin group and two in the animal insulin group, with no clear difference between the groups (RR 0.22, 95% CI 0.01 to 4.30). Perinatal death, pre-eclampsia, caesarean section, fetal anomaly, birth trauma including shoulder dystocia, nerve palsy and fracture and the composite outcome measure of neonatal morbidity were not reported.3. One trial (N = 93 women) compared pre-mixed insulin (70 NPH/30 REG) to self-mixed, split-dose insulin and provided very low-quality evidence to support the outcomes. Two cases of macrosomia were reported in the pre-mixed insulin group and four in the self-mixed insulin group, with no clear difference between the two groups (RR 0.49, 95% CI 0.09 to 2.54). There were seven cases of caesarean section (for cephalo-pelvic disproportion) in the pre-mixed insulin group and 12 in the self-mixed insulin group, with no clear difference between groups (RR 0.57, 95% CI 0.25 to 1.32). Perinatal death, pre-eclampsia, fetal anomaly, birth trauma including shoulder dystocia, nerve palsy, or fracture and the composite outcome measure of neonatal morbidity were not reported.4. In the same trial (N = 93 women), insulin injected with a Novolin pen was compared to insulin injected with a conventional needle (syringe), which provided very low-quality evidence to support the outcomes. There was one case of macrosomia in the pen group and five in the needle group, with no clear difference between the different insulin regimens (RR 0.21, 95% CI 0.03 to 1.76). There were five deliveries by caesarean section in the pen group compared with 14 in the needle group; women were less likely to deliver via caesarean section when insulin was injected with a pen compared to a conventional needle (RR 0.38, 95% CI 0.15 to 0.97). Perinatal death, pre-eclampsia, fetal anomaly, birth trauma including shoulder dystocia, nerve palsy, or fracture, and the composite outcome measure of neonatal morbidity were not reported.5. One trial (N = 223 women) comparing insulin Aspart with human insulin reported none of the review's primary outcomes: macrosomia, perinatal death, pre-eclampsia, caesarean section, fetal anomaly, birth trauma including shoulder dystocia. nerve palsy, or fracture, or the composite outcome measure of neonatal morbidity.6. One trial (N = 162 women) compared insulin Detemir with NPH insulin, and supported the outcomes with very low-quality evidence. There were three cases of major fetal anomalies in the insulin Detemir group and one in the NPH insulin group, with no clear difference between the groups (RR 3.15, 95% CI 0.33 to 29.67). Macrosomia, perinatal death, pre-eclampsia, caesarean section, birth trauma including shoulder dystocia, nerve palsy, or fracture and the composite outcome of neonatal morbidity were not reported.

AUTHORS' CONCLUSIONS

With limited evidence and no meta-analyses, as each trial looked at a different comparison, no firm conclusions could be made about different insulin types and regimens in pregnant women with pre-existing type 1 or 2 diabetes. Further research is warranted to determine who has an increased risk of adverse pregnancy outcome. This would include larger trials, incorporating adequate randomisation and blinding, and key outcomes that include macrosomia, pregnancy loss, pre-eclampsia, caesarean section, fetal anomalies, and birth trauma.

Maternal Circulating Lipid Profile during Early Pregnancy: Racial/Ethnic Differences and Association with Spontaneous Preterm Delivery

Prior reports on the association between altered maternal serum lipid levels with preterm delivery are inconsistent. Ethnic differences in serum lipids during pregnancy and their relation to preterm delivery have not been studied. We examined the relationships of six maternal lipids during early pregnancy with the risk of spontaneous preterm delivery (SPTD). The design represents a case-control study nested within a large prospective, multiethnic cohort of young, generally healthy pregnant women. SPTD cases (n = 183) and controls who delivered at term (n = 376) were included. SPTD is defined as delivery at <37 completed weeks of gestation without indicated conditions. We found that African-American women had significantly increased levels of high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A1 (apoA1), and lower triglyceride (TG) and apolipoprotein B (apoB) levels compared to Hispanic and non-Hispanic Caucasians combined. Elevated HDL-C and apoA1 concentrations were significantly associated with an increased odds of SPTD after controlling for potential confounding factors. The adjusted odds ratio (AOR) was 1.91 (95% confidence interval (CI) 1.15, 3.20) for the highest quartile of HDL-C relative to the lowest quartile, and for apoA1 the AOR was 1.94 (95% CI 1.16, 3.24). When controlling for ethnicity, the results remained comparable. These data suggest that pregnant African-American women had a more favorable lipid profile suggestive of a reduction in cardiovascular risk. Despite this, increased HDL-C and apoA1 were both found to be associated with SPTD.

Is maternal trait anxiety a risk factor for late preterm and early term deliveries?

Background

Anxiety is associated with preterm deliveries in general (before week 37 of pregnancy), but is that also true for late preterm (weeks 34/0–36/6) and early term deliveries (weeks 37/0–38/6)? We aim to examine this association separately for spontaneous and provider-initiated deliveries.

Methods

Participants were pregnant women from the Norwegian Mother and Child Cohort Study (MoBa), which has been following 95 200 pregnant women since 1999. After excluding pregnancies with serious health complications, 81 244 participants remained. National ultrasound records were used to delineate late preterm, early term, and full-term deliveries, which then were subdivided into spontaneous and provider-initiated deliveries. We measured trait anxiety based on two ratings of the anxiety items on the Symptom Checklist-8 (Acta Psychiatr Scand 87:364–7, 1993). Trait anxiety was transformed into categorizing the score at the mean and at ± 2 standard deviations.

Results

Trait anxiety was substantially associated with late preterm and early term deliveries after adjusting for confounders. In the whole sample, women with the highest anxiety scores (+2 standard deviations) were more likely [(odds ratio (OR) = 1.7; 95 % confidence-interval (CI) 1.3-2.0)] to delivering late preterm than women with the lowest anxiety scores. Their odds of delivering early term were also high (OR = 1.4; CI 1.3-1.6). Women with spontaneous deliveries and the highest anxiety scores had higher odds (OR = 1.4; CI 1.1-1.8) of delivering late preterm and early term (OR = 1.3; CI = 1.3-1.5). The corresponding odds for women with provider-initiated deliveries were OR = 1.7 (CI = 1.2-2.4) for late preterm and OR = 1.3 for early term (CI = 1.01-1.6). Irrespective of delivery onset, women with provider-initiated deliveries had higher levels of anxiety than women delivering spontaneously. However, women with high anxiety were equally likely to have provider-initiated or spontaneous deliveries.

Conclusions

This study is the first to show substantial associations between high levels of trait anxiety and late preterm delivery. Increased attention should be given to the mechanism underlying this association, including factors preceding the pregnancy. In addition, acute treatment should be offered to women displaying high levels of anxiety throughout pregnancy to avoid suffering for the mother and the child.

Cross-Country Individual Participant Analysis of 4.1 Million Singleton Births in 5 Countries with Very High Human Development Index Confirms Known Associations but Provides No Biologic Explanation for 2/3 of All Preterm Births

BACKGROUND

Preterm birth is the most common single cause of perinatal and infant mortality, affecting 15 million infants worldwide each year with global rates increasing. Understanding of risk factors remains poor, and preventive interventions have only limited benefit. Large differences exist in preterm birth rates across high income countries. We hypothesized that understanding the basis for these wide variations could lead to interventions that reduce preterm birth incidence in countries with high rates. We thus sought to assess the contributions of known risk factors for both spontaneous and provider-initiated preterm birth in selected high income countries, estimating also the potential impact of successful interventions due to advances in research, policy and public health, or clinical practice.

METHODS

We analyzed individual patient-level data on 4.1 million singleton pregnancies from four countries with very high human development index (Czech Republic, New Zealand, Slovenia, Sweden) and one comparator U.S. state (California) to determine the specific contribution (adjusting for confounding effects) of 21 factors. Both individual and population-attributable preterm birth risks were determined, as were contributors to cross-country differences. We also assessed the ability to predict preterm birth given various sets of known risk factors.

FINDINGS

Previous preterm birth and preeclampsia were the strongest individual risk factors of preterm birth in all datasets, with odds ratios of 4.6-6.0 and 2.8-5.7, respectively, for individual women having those characteristics. In contrast, on a population basis, nulliparity and male sex were the two risk factors with the highest impact on preterm birth rates, accounting for 25-50% and 11-16% of excess population attributable risk, respectively (p<0.001). The importance of nulliparity and male sex on population attributable risk was driven by high prevalence despite low odds ratios for individual women. More than 65% of the total aggregated risk of preterm birth within each country lacks a plausible biologic explanation, and 63% of difference between countries cannot be explained with known factors; thus, research is necessary to elucidate the underlying mechanisms of preterm birth and, hence, therapeutic intervention. Surprisingly, variation in prevalence of known risk factors accounted for less than 35% of the difference in preterm birth rates between countries. Known risk factors had an area under the curve of less than 0.7 in ROC analysis of preterm birth prediction within countries. These data suggest that other influences, as yet unidentified, are involved in preterm birth. Further research into biological mechanisms is warranted.

CONCLUSIONS

We have quantified the causes of variation in preterm birth rates among countries with very high human development index. The paucity of explicit and currently identified factors amenable to intervention illustrates the limited impact of changes possible through current clinical practice and policy interventions. Our research highlights the urgent need for research into underlying biological causes of preterm birth, which alone are likely to lead to innovative and efficacious interventions.

The global network antenatal corticosteroids trial: impact on stillbirth

Background

Antenatal corticosteroids are commonly used to reduce neonatal mortality, but most research to date has been in high-resource settings and few studies have evaluated its impact on stillbirth. In the Antenatal Corticosteroids Trial (ACT), a multi-country trial to assess impact of a multi-faceted intervention including antenatal corticosteroids to reduce neonatal mortality associated with preterm birth, we found an overall increase in 28-day neonatal mortality and stillbirth associated with the intervention.

Methods

The ACT was a cluster-randomized trial conducted in 102 clusters across 7 research sites in 6 countries (India [2 sites], Pakistan, Zambia, Kenya, Guatemala and Argentina), comparing an intervention to train birth attendants at all levels of the health system to identify women at risk of preterm birth, administer corticosteroids and refer women at risk. Because of inadequate gestational age dating, the <5^th percentile birth weight was used as a proxy for preterm birth. A pre-specified secondary outcome of the trial was stillbirth.

Results

After adjusting for the pre-trial imbalance in stillbirth rates, the ACT intervention was associated with a non-significant increased risk of stillbirth (aRR 1.08, 95 % CI, 0.99–1.17, p–0.073). Additionally, the stillbirth rate was higher in the term births (1.20 95 % CI 1.06–1.37, 0.004) and among those with signs of maceration (RR 1.18 (1.04–1.35), p = 0.013) in the intervention vs. control clusters. Differences in obstetric care favored the control clusters and maternal infection was likely more common in the intervention clusters.

Conclusions

In this pragmatic trial, limited data were available to identify the causes of the increase in stillbirths in the intervention clusters. A higher rate of stillbirth in the intervention clusters prior to the trial, differences in obstetric care and an increase in maternal infection are potential explanations for the observed increase in stillbirths in the intervention clusters during the trial.

Trial registration

clinicaltrials.gov (NCT01084096)

Assessing the Causal Relationship of Maternal Height on Birth Size and Gestational Age at Birth: A Mendelian Randomization Analysis

BACKGROUND

Observational epidemiological studies indicate that maternal height is associated with gestational age at birth and fetal growth measures (i.e., shorter mothers deliver infants at earlier gestational ages with lower birth weight and birth length). Different mechanisms have been postulated to explain these associations. This study aimed to investigate the casual relationships behind the strong association of maternal height with fetal growth measures (i.e., birth length and birth weight) and gestational age by a Mendelian randomization approach.

METHODS AND FINDINGS

We conducted a Mendelian randomization analysis using phenotype and genome-wide single nucleotide polymorphism (SNP) data of 3,485 mother/infant pairs from birth cohorts collected from three Nordic countries (Finland, Denmark, and Norway). We constructed a genetic score based on 697 SNPs known to be associated with adult height to index maternal height. To avoid confounding due to genetic sharing between mother and infant, we inferred parental transmission of the height-associated SNPs and utilized the haplotype genetic score derived from nontransmitted alleles as a valid genetic instrument for maternal height. In observational analysis, maternal height was significantly associated with birth length (p = 6.31 × 10-9), birth weight (p = 2.19 × 10-15), and gestational age (p = 1.51 × 10-7). Our parental-specific haplotype score association analysis revealed that birth length and birth weight were significantly associated with the maternal transmitted haplotype score as well as the paternal transmitted haplotype score. Their association with the maternal nontransmitted haplotype score was far less significant, indicating a major fetal genetic influence on these fetal growth measures. In contrast, gestational age was significantly associated with the nontransmitted haplotype score (p = 0.0424) and demonstrated a significant (p = 0.0234) causal effect of every 1 cm increase in maternal height resulting in ~0.4 more gestational d. Limitations of this study include potential influences in causal inference by biological pleiotropy, assortative mating, and the nonrandom sampling of study subjects.

CONCLUSIONS

Our results demonstrate that the observed association between maternal height and fetal growth measures (i.e., birth length and birth weight) is mainly defined by fetal genetics. In contrast, the association between maternal height and gestational age is more likely to be causal. In addition, our approach that utilizes the genetic score derived from the nontransmitted maternal haplotype as a genetic instrument is a novel extension to the Mendelian randomization methodology in casual inference between parental phenotype (or exposure) and outcomes in offspring.

Changes in antimüllerian hormone levels in early pregnancy are associated with preterm birth

OBJECTIVE

To determine the association of preterm birth with antimüllerian hormone (AMH) levels both in isolation and in combination with other markers of fetoplacental health commonly measured during integrated prenatal screening (IPS) for aneuploidy.

DESIGN

Retrospective case-control study.

SETTING

Not applicable.

PATIENT(S)

Pregnant women in Iowa who elected to undergo IPS and who subsequently delivered in Iowa, including women giving birth at <37 weeks' gestation and controls who delivered at ≥37 weeks' gestation.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Probability of a preterm birth.

RESULT(S)

Second trimester AMH levels were not associated with preterm birth, either independently or after controlling for other markers of fetoplacental health. The AMH difference was not associated with preterm birth when modeled alone, but a statistically significant association was found after adjusting for maternal serum α-fetoprotein (MSAFP) and maternal weight change between the first and second trimesters. After stratifying the model by MSAFP level, most of the risk for preterm birth was identified in women with an MSAFP >1 multiple of the median and who had a stable or rising AMH level in early pregnancy.

CONCLUSION(S)

A lack of decline in the AMH level in early pregnancy can be used to identify women with a high probability for preterm birth, especially when MSAFP levels are >1 multiple of the median. Monitoring changes in the AMH level between the first and second trimesters of pregnancy may help identify women who would benefit from interventional therapies such as supplemental progesterone.

Neutrophil elastase and fetal fibronectin levels as predictors of single-birth prematurity

The aim of this study was to investigate the predictive values (PVs) of neutrophil elastase (NE) and fetal fibronectin (fFN) in cervical secretions for single-birth premature delivery. Samples of cervical secretions were obtained from 144 women with high-risk singleton pregnancies at 20-34 weeks' gestation and premature Creasy scores of >12 points for NE and fFN level testing, and the PVs of the two indicators for premature birth (PB) were retrospectively analyzed. NE and fFN had high negative PVs (NPVs) for PB; the NPV of NE and fFN for delivery 7 days after detection was significantly higher than the positive PV (P<0.01). In addition, the sensitivity of the combined use of NE and fFN levels for PB prediction was high if both were present, and the PB rate of the double-positive group was higher than that of the single-positive group (P<0.01). Clinical intervention could turn the NE and fFN values negative in certain cases; in these cases, the PB rate was significantly lower than that in the sustained-positive group. In conclusion, NE and fFN in cervical secretions could be used as objective predictors of premature delivery, and their combined application could improve the prediction sensitivity. Effective clinical intervention could then reduce the incidence of PB.

The risk of preterm birth of treated versus untreated cervical intraepithelial neoplasia (CIN): a systematic review and meta-analysis

Cervical surgery is associated with preterm birth (PTB) and neonatal morbidity. However, it is unknown whether this increased risk is due to the surgery itself or to the cervical intraepithelial neoplasia (CIN) underlying the surgery. Our objective was to assess the risk for PTB in women with treated and untreated CIN. We performed an electronic literature search in MEDLINE, Embase and CENTRAL for studies that reported on pregnancy outcome after treated and untreated CIN. The methodological quality was scored using the STROBE combined checklist for observational studies. We extracted data on PTB<37 weeks, very PTB<32 weeks, spontaneous PTB<37 weeks, (preterm) premature rupture of membranes ((P)PROM), perinatal mortality and section caesarean each before and after treatment for CIN. We used the Mantel-Haenszel method to estimate summarizing odds ratios. Our search identified 620 studies, of which 20 were reporting on pregnancy outcome for a total of 12,159,293 women. There were 20,832 women who gave birth after treatment for CIN before pregnancy, 52 women who gave birth after treatment for CIN during pregnancy, 64,237 women with CIN who gave birth before treatment, and 8,902,865 women who gave birth without CIN. Compared to women with untreated CIN, women treated for CIN before or during pregnancy, had a significantly higher risk of PTB<37 weeks (OR 1.7, 95% CI 1.0-2.7). When comparing women treated for CIN before pregnancy (n=20,832) to women with untreated CIN (n=64,162), we found an OR of 1.4 with a 95% confidence interval of 0.85-2.3. Women treated during pregnancy had a clearly increased risk for PTB (OR 6.5, 95% CI 1.1-37), and (P)PROM (OR 1.8, 95% CI 1.4-2.2). In women with cervical surgery, the risks for spontaneous PTB<37 weeks (OR 0.87, 95% CI 0.54-1.4), caesarean section (OR 1.0, 95% CI 0.71-1.5) and perinatal mortality (OR 1.0, 95% CI 0.38-2.8) were not increased. The increased risk of PTB in women who underwent cervical surgery for CIN is especially increased when performed during pregnancy. When performed before pregnancy the risk of PTB is increased, although insignificant.

Is universal cervical length screening indicated in women with prior term birth?

OBJECTIVE

To determine whether universal transvaginal ultrasound (TVU) cervical length (CL) screening is indicated in women with prior term births.

STUDY DESIGN

We conducted a prospective cohort study from Jan. 1, 2012, to June 30, 2013, of singleton gestations between 18 0/7-23 6/7 weeks undergoing TVU CL screening for prediction of spontaneous preterm birth (sPTB). Women with a prior sPTB, with cerclage, and without delivery data available were excluded. Primary outcomes were the incidence of a CL ≤20 mm, and rates of sPTB <37, <34, and <32 weeks gestation among women with prior term births vs nulliparous women.

RESULTS

A total of 1569 women underwent TVU CL screening; 18 women with a prior iatrogenic preterm birth were excluded. Of those screened, 756 (48.7%) had a prior term delivery and 795 (51.3%) were nulliparous. Women with prior term births differed from nulliparous women with respect to age, body mass index, race, smoking status, and prior dilation and curettage. After adjustment for these confounders, there was no statistical difference in the incidence of CL ≤20 mm (0.8 vs 1.4%; adjusted odds ratio, 0.35; 95% confidence interval, 0.12-1.03) among women with prior term births compared with nulliparous women. Rates of sPTB <37, <34, <32 weeks were similar in women with a prior term birth compared with nulliparous women. The overall incidence of sPTB <37 weeks was 3.2% in women with a prior term birth and 5.0% in nulliparous women. When a CL ≤20 mm was identified, 3 of 6 women with prior term birth delivered at <37 weeks compared with 8 of 11 nulliparous women. There were no identified differences between the odds of sPTB between women with a CL ≤20 mm who had a prior term birth compared with nulliparous women.

CONCLUSION

Women with prior term birth have a trend toward a lower incidence of CL ≤20 mm, compared with nulliparous women. Further studies are needed to determine whether women with prior term births should be included or excluded from TVU CL screening.

Preterm subtypes by immigrants' length of residence in Norway: a population-based study

Background

The reduction of the preterm delivery (PTD) rate is a maternal and child health target. Elevated rates have been found among several immigrant groups, but few studies have distinguished between PTD according to the mode of birth start. In addition, migrants’ birth outcomes have further been shown to be affected by the time in residence; however, the association to PTD subtypes has not previously been assessed. In this study we examined if the risk of spontaneous and non-spontaneous, or iatrogenic, PTD among immigrants in Norway varied according to the length of residence and the country of birth, and compared with the risks among the majority population.

Methods

We linked population-based birth and immigration data for 40 709 singletons born to immigrant women from Iraq, Pakistan, the Philippines, Somalia, Sri Lanka and Vietnam and 868 832 singletons born to non-immigrant women from 1990–2009. Associations between the length of residence and subtypes of PTD were estimated as relative risks (RRs) with 95% confidence intervals (CIs) from multivariable models.

Results

In total, 48 191 preterm births occurred. Both spontaneous and non-spontaneous PTD rates were higher among immigrants (4.8% and 2.0%) than among non-immigrants (3.6% and 1.6%). Only non-spontaneous PTD was associated with longer lengths of residence (p trend <0.001). Recent immigrants (<5 years of residence) and non-immigrants had a similar risk of non-spontaneous PTD, whereas immigrants with lengths of residence of 5–9 years, 10–14 years and ≥15 years had adjusted RRs of 1.18 [95% CI 1.03,1.35], 1.43 [95% CI 1.20,1.71] and 1.66 [95% CI 1.41,1.96]. The association was reduced after further adjustments for maternal and infant morbidity. Conversely, the risk of spontaneous PTD among immigrants was not mitigated by length of residence, but varied with country of birth according to the duration of pregnancy in term births.

Conclusions

Non-spontaneous PTD increased with the length of residence whereas spontaneous PTD remained elevated regardless of the length of residence. Policies to improve birth outcomes in ethnically mixed populations should address the modifiable causes of PTD rather than aiming to reduce absolute PTD rates.