Is there a role for cervical assessment and uterine artery Doppler in the first trimester of pregnancy as a screening test for spontaneous preterm delivery?

First-Trimester Prediction Models Based on Maternal Characteristics for Adverse Pregnancy Outcomes: A Systematic Review and Meta-Analysis

BACKGROUND

Early risk stratification can facilitate timely interventions for adverse pregnancy outcomes, including preeclampsia (PE), small-for-gestational-age neonates (SGA), spontaneous preterm birth (sPTB) and gestational diabetes mellitus (GDM).

OBJECTIVES

To perform a systematic review and meta-analysis of first-trimester prediction models for adverse pregnancy outcomes.

SEARCH STRATEGY

The PubMed database was searched until 6 June 2024.

SELECTION CRITERIA

First-trimester prediction models based on maternal characteristics were included. Articles reporting on prediction models that comprised biochemical or ultrasound markers were excluded.

DATA COLLECTION AND ANALYSIS

Two authors identified articles, extracted data and assessed risk of bias and applicability using PROBAST.

MAIN RESULTS

A total of 77 articles were included, comprising 30 developed models for PE, 15 for SGA, 11 for sPTB and 35 for GDM. Discriminatory performance in terms of median area under the curve (AUC) of these models was 0.75 [IQR 0.69-0.78] for PE models, 0.62 [0.60-0.71] for SGA models of nulliparous women, 0.74 [0.72-0.74] for SGA models of multiparous women, 0.65 [0.61-0.67] for sPTB models of nulliparous women, 0.71 [0.68-0.74] for sPTB models of multiparous women and 0.71 [0.67-0.76] for GDM models. Internal validation was performed in 40/91 (43.9%) of the models. Model calibration was reported in 21/91 (23.1%) models. External validation was performed a total of 96 times in 45/91 (49.5%) of the models. High risk of bias was observed in 94.5% of the developed models and in 58.3% of the external validations.

CONCLUSIONS

Multiple first-trimester prediction models are available, but almost all suffer from high risk of bias, and internal and external validations were often not performed. Hence, methodological quality improvement and assessment of the clinical utility are needed.

Effect of combination of uterine artery doppler and vitamin D level on perinatal outcomes in second trimester pregnant women

OBJECTIVES

To investigate the effect of the combination of uterine artery (UtA) Doppler and vitamin D levels on perinatal outcomes in second trimester pregnants was aimed.

METHODS

UtA Dopplers and vitamin D levels of 226 pregnant women in the second trimester were measured. Patients were followed for adverse pregnancy outcomes. The relationship of this combination with these pregnancy outcomes was evaluated.

RESULTS

Sensitivity and specificity values ​​are respectively; Left UtA-S/D ratio for preeclampsia was 85.29 and 81.77 %, left UtA-RI was 90.62 and 43.30 % for preterm birth, and 76.19 and 66.34 % for the development of fetal distress had the best predictive effect. Vitamin D values ​​had no predictive value for any parameter (p>0.005).

CONCLUSIONS

UtA Doppler has a good predictive value for many adverse pregnancy outcomes. However, in order to correlate these results with second trimester vitamin D levels, more homogeneous and specific groups are needed.

Cervical length measurement between 11 and 13 + 6 weeks of pregnancy: Comparison of maternal and ultrasonographic characteristics between term and preterm deliveries

OBJECTIVE

The aim of this study was to evaluate the maternal and ultrasonographic characteristics of pregnant women who underwent cervical length (CL) measurement by transvaginal ultrasound between 11 and 13 + 6 weeks of gestation and who delivered at term or preterm.

METHODS

A retrospective cohort study was carried out between March 2013 and December 2018 by analyzing ultrasound data of singleton pregnant women who underwent CL measurement by transvaginal ultrasound during the first trimester scan. CL was compared between the two groups (full-term and preterm birth [PB]) using Student's t-test.

RESULTS

A total of 5097 pregnant women were enrolled, of whom 5061 (99.3%) had term and 36 (0.7%) had PB < 34 weeks. CL measurements did not differ between the term and preterm groups (36.62 vs. 37.83 mm, p = 0.08). Maternal age showed a significant and linear association with CL (r = 0.034, p = 0.012) and CRL (r = 0.086, p < 0.001). Smoking status was associated with shorter CL (36.64 vs. 35.09 mm, p = 0.003). When we analyzed the CL of the pregnant women in the term and preterm groups, according to the gestational age cut-offs for prematurity (28, 30, 32, and 34 weeks), we found that there was no significant difference between the measurements in all groups (p > 0.05).

CONCLUSION

We observed no significant differences between CL measurements between 11 and 13 + 6 weeks in pregnant women who had preterm and term deliveries. Gestational age and CRL showed a significant and linear association with CL measurement.

First-trimester and early-second-trimester transvaginal cervical length before 16 weeks among women with preterm and term birth: a systematic review and meta-analysis

OBJECTIVE

This study aimed to evaluate the differences in first-trimester and early-second-trimester transvaginal cervical length between patients with spontaneous preterm birth and those with term birth.

DATA SOURCES

PubMed, MEDLINE, Embase, and the Cochrane Library were systematically searched through August 2023.

STUDY ELIGIBILITY CRITERIA

Studies had to include (1) transvaginal cervical length measurement before 16+0 weeks of gestation and (2) transvaginal cervical length measurement in a population of patients who delivered preterm and at term. Abstracts, studies with duplicated data, and those with cervical length measured by transabdominal ultrasound scan were excluded.

METHODS

K.W.C. and J.L. searched for, screened, and reviewed the articles independently. The quality of the studies was assessed using the Newcastle-Ottawa scale. Mean differences were calculated using a random-effects model and pooled through a meta-analysis.

RESULTS

A total of 5727 published articles were identified. Only 10 studies (which analyzed 22,151 pregnancies) met the inclusion criteria. All studies excluded iatrogenic preterm birth. Transvaginal cervical length was significantly shorter in women with spontaneous preterm birth than in those who delivered at term (mean difference, -0.97; 95% confidence interval, -1.65 to -0.29; P=.005; I2=69%). When a linear technique was used to measure transvaginal cervical length, a significantly shorter transvaginal cervical length was associated with spontaneous preterm birth as opposed to term birth (mean difference, -1.09; 95% confidence interval, -1.96 to -0.21; P=.02; I2=77%). A shorter transvaginal cervical length measured by other techniques was also associated with spontaneous preterm birth before 34 to 35 weeks (mean difference, -1.87; 95% confidence interval, -3.04 to -0.70; P=.002; I2=0%). When studies where interventions were given for a "short" cervix or studies with a mean transvaginal cervical length ≥40 mm were excluded, a significantly shorter transvaginal cervical length was observed among those with spontaneous preterm birth (mean difference, -1.13; 95% confidence interval, -1.89 to -0.37; P=.004; mean difference, -0.86; 95% confidence interval, -1.67 to -0.04; P=.04; respectively). The optimal transvaginal cervical length cutoff was 38 to 39 mm, yielding pooled sensitivity of 0.80, specificity of 0.45, positive likelihood ratio of 1.16, negative likelihood ratio of 0.33, diagnostic odds ratio of 5.12, and an area under the curve of 0.75.

CONCLUSION

Women with spontaneous preterm birth had significantly shorter transvaginal cervical length before 16 weeks of gestation compared with those who delivered at term. The linear method and the 2-line method are acceptable techniques for measuring transvaginal cervical length.

Blood pressure trajectories during pregnancy and preterm delivery: A prospective cohort study in China

Women's blood pressure (BP) changes throughout pregnancy. The effect of BP trajectories on preterm delivery is not clear. The authors aim to evaluate the association between maternal BP trajectories during pregnancy and preterm delivery. The authors studied pregnant women included in the Born in Guangzhou Cohort Study in China between February 2012 and June 2016. Maternal BP was measured at antenatal visits between 13 and 40 gestational weeks, and gestational age of delivery data was collected. The authors used linear mixed models to capture the BP trajectories of women with term, and spontaneous and iatrogenic preterm delivery. BP trajectories of women with various gestational lengths (34, 35, 36, 37, 38, 39, 40 weeks) were compared. Of the 17 426 women included in the analysis, 618 (3.55%) had spontaneous preterm delivery; 158 (.91%) had iatrogenic preterm delivery; and 16 650 (95.55%) women delivered at term. The BP trajectories were all J‐shaped curves for different delivery types. Women with iatrogenic preterm delivery had the highest mean BP from 13 weeks till delivery, followed by those with spontaneous preterm delivery and term delivery (p < .001). Trajectory analysis stratified by maternal parity showed similar results for nulliparous and multiparous women. Excluding women with pre‐eclampsia and gestational hypertension (GH) significantly attenuated the aforementioned association. Also, women with shorter gestational length tend to have higher BP trajectories during pregnancy. In conclusion, Women with spontaneous preterm delivery have a higher BP from 13 weeks till delivery than women with term delivery, while women with iatrogenic preterm delivery have the highest BP.

Screening for spontaneous preterm birth by cervical length and shear-wave elastography in the first trimester of pregnancy

BACKGROUND

First-trimester cervical length for the prediction of spontaneous preterm delivery remains controversial. A better method for the measurement of the first-trimester cervical length and additional cervical ultrasound parameters for the identification of women at high risk for spontaneous preterm delivery are needed.

OBJECTIVE

This study aimed to compare the predictive value of cervical length measured by 2 different methods in the first trimester of pregnancy to predict spontaneous preterm delivery and to explore the potential value of first-trimester cervical shear-wave elastography for the prediction of spontaneous preterm delivery.

STUDY DESIGN

This was a prospective study in unselected singleton pregnancies at 11⁺⁰ to 13⁺⁶ weeks' gestation. Cervical length was measured by the following 2 methods in the base-cohort population: (1) a linear distance between the 2 ends of the glandular area around the endocervical canal (single-line method: cervical length-s) and (2) a sum of the linear distance from the internal os to the greatest cervical curvature and the linear distance from this point to the external os (2-line method: cervical length-t). In a substudy, cervical shear-wave elastography scores for 9 regions of interest (inner, middle, and external parts of anterior lip, endocervical canal, and posterior lip) in midsagittal plane were also obtained by transvaginal ultrasonography. The screening performance of the first-trimester cervical length measured by the 2 different methods for the prediction of spontaneous preterm delivery was assessed by receiver operating characteristics curve analysis. The areas under the curves were compared using a DeLong test. The predictive performance of a soft cervix (mean elastography scores with multiple of median <5th, 10th, 15th, 20th, and 25th percentile) for spontaneous preterm delivery was also determined.

RESULTS

Among a total of 2316 included pregnancies, spontaneous delivery at <37 and <34 weeks' gestation occurred in 111 cases (4.8%) and 20 cases (0.9%), respectively. In the total study population, when compared with the term delivery group, the median cervical length-t was shorter in women with spontaneous delivery at <34 weeks' gestation (36.9 mm vs 35.1 mm; P=.015), but there was no clear correlation for cervical length-s. Receiver operating characteristics curves demonstrated that cervical length-t achieved better performance in predicting spontaneous delivery at <34 weeks' gestation (area under the curve, 0.658 vs 0.573; P<.01) than cervical length-s. The best combined model to predict spontaneous delivery at <34 weeks' gestation was provided by cervical length-t and history of preterm delivery (area under the curve, 0.692). In the substudy, a soft cervix with a mean elastography scores multiple of median <10th percentile had a relative risk of 7.8 (95% confidence interval, 2.1-28.6) for spontaneous delivery at <34 weeks' gestation; the detection rate was 44.4% at a false-positive rate of 9.0%.

CONCLUSION

The 2-line approach provides a better estimate of the actual first-trimester cervical length and achieves better performance as a screening tool for spontaneous preterm delivery at <34 weeks' gestation than the conventional measurement. A soft cervix as determined by shear-wave elastograpthy in the first trimester is associated with an increased risk for subsequent spontaneous preterm delivery.

A Review of Roles of Uterine Artery Doppler in Pregnancy Complications

The invasion of trophoblasts into the uterine decidua and decidual vessels is critical for the formation of placenta. The defects of placentation are related to the etiologies of preeclampsia (PE), fetal growth restriction (FGR), and small-for-gestational age (SGA) neonates. It is possible to predict significant vascular events during pregnancy through uterine artery Doppler (UAD). From the implantation stage to the end of pregnancy, detecting changes in uterine and placental blood vessels can provide a favorable diagnostic instrument for pregnancy complications. This review aims to collect literature about the roles of UAD in pregnancy complications. We consider all relevant articles in English from January 1, 1983 to October 30, 2021. Predicting pregnancy complications in advance allows practitioners to carry out timely interventions to avoid or lessen the harm to mothers and neonates. Administering low-dose aspirin daily before 16 weeks of pregnancy can significantly reduce the incidence of pregnancy complications. From early pregnancy to late pregnancy, UAD can combine with other maternal factors, biochemical indicators, and fetal measurement data to identify high-risk population. The identification of high-risk groups can also lessen maternal mortality. Besides, through moderate risk stratification, stringent monitoring for high-risk pregnant women can be implemented, decreasing the incidence of adversities.

Prediction of spontaneous preterm birth by cervical length in the first trimester of pregnancy: Comparison of two measurement methods

INTRODUCTION

Our objectives were to compare the single-line and two-line methods of cervical length measurement in the first trimester of pregnancy and to evaluate the potential value of the first trimester cervical length measured by the two methods in predicting spontaneous preterm birth.

MATERIAL AND METHODS

This was a prospective study in singleton pregnancies at 11+0 to 13+6  weeks of gestation. Cervical length was measured by two methods: (i) a linear distance between the two ends of the glandular area around the endocervical canal (single-line method) and (ii) a sum of a linear distance from the internal os to the greatest cervical curvature and a linear distance from this point of the cervix to the external os (two-line method). The screening performance of the first trimester cervical length measured by the two different methods for the prediction of spontaneous preterm delivery was assessed by receiver-operating characteristics (ROC) curve analysis. The areas under the ROC (AUROC) were compared by De Long test.

RESULTS

A total of 1484 consecutive singleton pregnancies were included in this study. Spontaneous preterm delivery at <37 and <32 weeks occurred in 75 cases (5.1%) and 12 cases (0.8%), respectively. The median cervical length measured by the single-line method was significantly shorter than that by the two-line method (33.5 vs 36.5 mm, p < .001). Compared with the term delivery group, the median cervical length measured by the two-line method was shorter in women with spontaneous delivery at <32 weeks of gestation (36.5 vs 33.6 mm, p < .01). No significant difference in the median cervical length measured by the single-line method was detected between the spontaneous preterm delivery and term delivery groups. Receiver-operating-characteristic curves demonstrated that cervical length measured by the two-line method achieved better performance in predicting spontaneous delivery at <32 weeks compared with the single-line method (AUROC: 0.72 vs 0.61, p < .01).

CONCLUSIONS

We have demonstrated that the first trimester cervical length, measured by the two-line approach, holds promise as a potential screening tool for early spontaneous preterm delivery.

The predictive capacity of uterine artery Doppler for preterm birth-A cohort study

Introduction

Mid‐trimester uterine artery resistance measured with Doppler sonography is predictive for iatrogenic preterm birth. In view of the emerging association between hypertensive disease in pregnancy and spontaneous preterm birth, we hypothesized that uterine artery resistance could also predict spontaneous preterm birth.

Material and methods

We performed a cohort study of women with singleton pregnancies. Uterine artery resistance was routinely measured at the 18‐22 weeks anomaly scan. Pregnancies complicated by congenital anomalies or intrauterine fetal death were excluded. We analyzed if the waveform of the uterine artery (no notch, unilateral notch or bilateral notch) was predictive for spontaneous and iatrogenic preterm birth, defined as delivery before 37 weeks of gestation. Furthermore, we assessed whether the uterine artery pulsatility index was associated with the risk of preterm birth.

Results

Between January 2009 and December 2016 we collected uterine Doppler indices and relevant outcome data in 4521 women. Mean gestational age at measurement was 19⁺⁶ weeks. There were 137 (3.0%) women with a bilateral and 213 (4.7%) with a unilateral notch. Mean gestational age at birth was 38⁺⁶ weeks. Spontaneous and iatrogenic preterm birth rates were 5.7% and 4.9%, respectively. Mean uterine artery resistance was 1.12 in the spontaneous preterm birth group compared with 1.04 in the term group (P = 0.004) The risk of preterm birth was increased with high uterine artery resistance (OR 2.9 per unit; 95% CI 2.4‐3.9). Prevalence of spontaneous preterm birth increased from 5.5% in women without a notch in the uterine arteries to 8.0% in women with a unilateral notch and 8.0% in women with a bilateral notch. For iatrogenic preterm birth, these rates were 3.9%, 13.6% and 23.4%, respectively. Likelihood ratios for the prediction of spontaneous preterm birth were 1.6 (95% CI 1.0‐2.6) and 1.9 (95% CI 1.0‐3.5) for unilateral and bilateral notches, respectively, and for iatrogenic preterm birth they were 3.6 (95% CI 2.5‐5.2) and 6.8 (95% CI 4.7‐9.9) for unilateral and bilateral notches, respectively. Of all women with bilateral notching, 31.4% delivered preterm.

Conclusions

Mid‐trimester uterine artery resistance measured at 18‐22 weeks of gestation is a weak predictor of spontaneous preterm birth.

The prediction of early preeclampsia: Results from a longitudinal proteomics study

OBJECTIVES

To identify maternal plasma protein markers for early preeclampsia (delivery <34 weeks of gestation) and to determine whether the prediction performance is affected by disease severity and presence of placental lesions consistent with maternal vascular malperfusion (MVM) among cases.

STUDY DESIGN

This longitudinal case-control study included 90 patients with a normal pregnancy and 33 patients with early preeclampsia. Two to six maternal plasma samples were collected throughout gestation from each woman. The abundance of 1,125 proteins was measured using high-affinity aptamer-based proteomic assays, and data were modeled using linear mixed-effects models. After data transformation into multiples of the mean values for gestational age, parsimonious linear discriminant analysis risk models were fit for each gestational-age interval (8-16, 16.1-22, 22.1-28, 28.1-32 weeks). Proteomic profiles of early preeclampsia cases were also compared to those of a combined set of controls and late preeclampsia cases (n = 76) reported previously. Prediction performance was estimated via bootstrap.

RESULTS

We found that 1) multi-protein models at 16.1-22 weeks of gestation predicted early preeclampsia with a sensitivity of 71% at a false-positive rate (FPR) of 10%. High abundance of matrix metalloproteinase-7 and glycoprotein IIbIIIa complex were the most reliable predictors at this gestational age; 2) at 22.1-28 weeks of gestation, lower abundance of placental growth factor (PlGF) and vascular endothelial growth factor A, isoform 121 (VEGF-121), as well as elevated sialic acid binding immunoglobulin-like lectin 6 (siglec-6) and activin-A, were the best predictors of the subsequent development of early preeclampsia (81% sensitivity, FPR = 10%); 3) at 28.1-32 weeks of gestation, the sensitivity of multi-protein models was 85% (FPR = 10%) with the best predictors being activated leukocyte cell adhesion molecule, siglec-6, and VEGF-121; 4) the increase in siglec-6, activin-A, and VEGF-121 at 22.1-28 weeks of gestation differentiated women who subsequently developed early preeclampsia from those who had a normal pregnancy or developed late preeclampsia (sensitivity 77%, FPR = 10%); 5) the sensitivity of risk models was higher for early preeclampsia with placental MVM lesions than for the entire early preeclampsia group (90% versus 71% at 16.1-22 weeks; 87% versus 81% at 22.1-28 weeks; and 90% versus 85% at 28.1-32 weeks, all FPR = 10%); and 6) the sensitivity of prediction models was higher for severe early preeclampsia than for the entire early preeclampsia group (84% versus 71% at 16.1-22 weeks).

CONCLUSION

We have presented herein a catalogue of proteome changes in maternal plasma proteome that precede the diagnosis of preeclampsia and can distinguish among early and late phenotypes. The sensitivity of maternal plasma protein models for early preeclampsia is higher in women with underlying vascular placental disease and in those with a severe phenotype.

Prediction of Preterm Birth: Maternal Characteristics, Ultrasound Markers, and Biomarkers: An Updated Overview

There is not a single or combined screening method for preterm birth with high sensitivity which will truly identify the women at risk for preterm birth while also with high specificity to prevent unnecessary interventions and high treatment costs. Measurement of cervical length is the most cost-effective method that is used in clinical practice. Bedside tests have also been developed for detecting markers like fetal fibronectin, insulin-like growth factor binding protein-1 (IGFBP-1), interleukin-6, and placental alpha-macroglobulin-1. Taking the maternal history, health condition, and sociodemographical factors into consideration is recommended. Ultrasound markers apart from cervical length measurements as uterocervical angle and placental strain ratio are studied. Investigations on metabolomics, proteomics, and microRNA profiling have brought a new aspect on this subject. Maybe in the future, with clear identification of women at true risk for preterm birth, development of more effective preventive strategies will not be unfeasible.

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.

Prediction models for the risk of spontaneous preterm birth based on maternal characteristics: a systematic review and independent external validation

Introduction

Prediction models may contribute to personalized risk‐based management of women at high risk of spontaneous preterm delivery. Although prediction models are published frequently, often with promising results, external validation generally is lacking. We performed a systematic review of prediction models for the risk of spontaneous preterm birth based on routine clinical parameters. Additionally, we externally validated and evaluated the clinical potential of the models.

Material and methods

Prediction models based on routinely collected maternal parameters obtainable during first 16 weeks of gestation were eligible for selection. Risk of bias was assessed according to the CHARMS guidelines. We validated the selected models in a Dutch multicenter prospective cohort study comprising 2614 unselected pregnant women. Information on predictors was obtained by a web‐based questionnaire. Predictive performance of the models was quantified by the area under the receiver operating characteristic curve (AUC) and calibration plots for the outcomes spontaneous preterm birth <37 weeks and <34 weeks of gestation. Clinical value was evaluated by means of decision curve analysis and calculating classification accuracy for different risk thresholds.

Results

Four studies describing five prediction models fulfilled the eligibility criteria. Risk of bias assessment revealed a moderate to high risk of bias in three studies. The AUC of the models ranged from 0.54 to 0.67 and from 0.56 to 0.70 for the outcomes spontaneous preterm birth <37 weeks and <34 weeks of gestation, respectively. A subanalysis showed that the models discriminated poorly (AUC 0.51–0.56) for nulliparous women. Although we recalibrated the models, two models retained evidence of overfitting. The decision curve analysis showed low clinical benefit for the best performing models.

Conclusions

This review revealed several reporting and methodological shortcomings of published prediction models for spontaneous preterm birth. Our external validation study indicated that none of the models had the ability to predict spontaneous preterm birth adequately in our population. Further improvement of prediction models, using recent knowledge about both model development and potential risk factors, is necessary to provide an added value in personalized risk assessment of spontaneous preterm birth.

Reference ranges for the uterine arteries Doppler and cervical length measurement at 11-13(+6) weeks of gestation in a Brazilian population

OBJECTIVE

To establish references ranges for the uterine arteries (UtA) Doppler and cervical length (CL) measurements at 11-13(+6) weeks of gestation in a Brazilian population.

METHODS

We performed a retrospective cross-sectional study with singleton low-risk pregnant women who underwent first trimester ultrasound exams of fetuses with crown-rump length (CRL) ranging from 45 to 84 mm. The mean UtA Doppler and CL measurements were performed by transvaginal route. The mean pulsatility index (PI) of uterine arteries was obtained with color Doppler at the level of cervico-corporeal junction. The CL was obtained in a sagittal view using the cervical gland area as landmark. We determined mean ± standard deviation (SD), ranges for mean PI of UtA and CL in each gestational age. Polynomial regression was performed to establish reference values.

RESULTS

We have assessed 598 first-trimester pregnancies: the CL measurement was obtained from 497, while the mean PI UtA Doppler was available in 450 pregnant women. The mean CL ranged from 33.41 to 35.58 mm while the PI UtA Doppler ranged from 1.89 to 1.45. The best fit curves were: CL = 30.790 + 0.057 × CRL and UtA PI = 2.411-0.011 × CRL.

CONCLUSION

References ranges for the mean UtA PI Doppler and CL measurement at 11-13(+6) weeks of gestation in a Brazilian population were established.

Prediction of Preterm Delivery by Late Cervical Length Measurement after 24 Weeks

Objective: To examine the value of the cervical length (CL) measurement at 24-30 gestational weeks in the prediction of spontaneous preterm delivery (SPD) between 30 and 34 weeks (SPD34) and between 34 and 37 weeks (SPD37). Methods: We performed a prospective cross-sectional study. CL was measured once by transvaginal ultrasound examination between 24 and 30 weeks. Results: The study sample consisted of 1,180 low-risk singleton pregnancies. 10 women (0.85%) had a SPD34 and 60 (5.08%) had a SPD37. CL was shorter (p < 0.001) in the women who had a SPD34 (median 11 mm) compared to the women who delivered after 34 weeks (median 31 mm). CL was shorter (p < 0.001) in the women who had a SPD37 (median 22 mm) compared to the women who delivered after 37 weeks (median 31 mm). CL predicted SPD34 (OR = 0.837, R2 = 0.2768, AUC = 0.9406, p < 0.001) and SPD37 (OR = 0.907, R2 = 0.1085, AUC = 0.7584, p < 0.001). The model achieved a sensitivity of 70.0 and 38.3% for 10% false-positive rate for SPD34 and SPD37, respectively. Conclusions: CL after 24 weeks is significantly shorter in women destined to have a SPD. In low-risk singleton pregnancies CL performs very well in predicting SPD34 and adequately in predicting SPD37.

Cervical length in late second and third trimesters: a mixture model for predicting delivery

OBJECTIVES

To examine the distribution of cervical length (CL) in the late second and third trimesters of pregnancy and construct survival models for spontaneous delivery.

METHODS

This cross-sectional study included 647 women with a singleton pregnancy who had routine CL measurements taken by transvaginal ultrasonography between 24 and 40 weeks' gestation. Only one measurement per patient was included in the analysis. Exploratory data analysis revealed that the distribution of CL measurements was a mixture of two Gaussian distributions, and subsequently a mixture model was applied to describe the distribution of CL. Changes in CL in relation to gestational age were examined by regression analysis and measurements were converted to Z-scores. Survival analysis was applied to the subgroups identified, to describe the probability of delivery throughout gestation.

RESULTS

CL was best described by a mixture model of two subgroups with Gaussian distribution, one including women with a long cervix (73.85% of the study population, mean CL of 28.2 ± 4.45 mm) and the other including women with a short cervix (26.15% of the study population, mean CL of 12.3 ± 5.14 mm). CL was dependent on gestational age (GA), therefore conversion to Z-scores was employed in the analysis. Women with a short cervix had a higher probability for spontaneous delivery (hazard ratio (HR), 1.807; P < 0.001) than did women with a long cervix, after adjustment for GA at the time of measurement (GA HR, 1.115; P < 0.001). In both subgroups, the probability of spontaneous delivery was predicted by the GA and CL Z-scores. Survival models for the prediction of spontaneous delivery were constructed separately for the short-cervix subgroup (GA HR, 1.085; P < 0.001 and CL Z-score HR, 0.819; P = 0.003) and the long-cervix subgroup (GA HR, 1.130; P < 0.001 and CL Z-score HR, 0.864; P = 0.005).

CONCLUSIONS

CL follows a mixture of two Gaussian distributions, one for a short and one for a long cervix. Late second-trimester/third-trimester CL measurement may be of value in estimating the probability for spontaneous delivery at any given gestational age.

First trimester screening can predict adverse pregnancy outcomes

There has been an increasing drive over the last two decades to push the detection of women at risk of adverse pregnancy outcomes into the first trimester. This has led to a plethora of techniques, risk assessments and biomarkers, both fascinating and bewildering in its breadth. Despite the vast amount of knowledge available, it is often difficult to determine what is practicable and valuable for clinical practice. This is especially true as earlier diagnosis does not necessarily equate to improved outcomes for mother and child. We suggest that, at least for preeclampsia, fetal growth restriction, spontaneous preterm birth and gestational diabetes, there are effective first trimester tests available to identify the women at risk of subsequently developing complications. Unfortunately, there are no currently reliable first trimester tests available for identifying women at risk of stillbirth. It is likely that this field will continue to develop over time, and we hope that new and better strategies will continue to emerge to target these clinically important pathologies.

First trimester biomarkers in the prediction of later pregnancy complications

Adverse obstetric outcomes, such as preeclampsia, preterm birth, gestational diabetes, and fetal growth restriction, are poorly predicted by maternal history and risk factors alone, especially in nulliparae. The ability to predict these outcomes from the first trimester would allow for the early initiation of prophylactic therapies, institution of an appropriate model and location of care, and recruitment of a truly "high risk" population to clinical trials of interventions to prevent or ameliorate these conditions. To this end, development of adequately sensitive and specific predictive tests for these outcomes has become a significant focus of perinatal research. This paper reviews the biomarkers involved in these multiparametric tests and also outlines the performance of these tests and issues regarding their introduction into clinical practice.