Predictive value of cervical length in women with twin pregnancy presenting with threatened preterm labor

Preterm Birth: Screening and Prediction

Preterm birth (PTB) affects approximately 10% of births globally each year and is the most significant direct cause of neonatal death and of long-term disability worldwide. Early identification of women at high risk of PTB is important, given the availability of evidence-based, effective screening modalities, which facilitate decision-making on preventative strategies, particularly transvaginal sonographic cervical length (CL) measurement. There is growing evidence that combining CL with quantitative fetal fibronectin (qfFN) and maternal risk factors in the extensively peer-reviewed and validated QUanititative Innovation in Predicting Preterm birth (QUiPP) application can aid both the triage of patients who present as emergencies with symptoms of preterm labor and high-risk asymptomatic women attending PTB surveillance clinics. The QUiPP app risk of delivery thus supports shared decision-making with patients on the need for increased outpatient surveillance, in-patient treatment for preterm labor or simply reassurance for those unlikely to deliver preterm. Effective triage of patients at preterm gestations is an obstetric clinical priority as correctly timed administration of antenatal corticosteroids will maximise their neonatal benefits. This review explores the predictive capacity of existing predictive tests for PTB in both singleton and multiple pregnancies, including the QUiPP app v.2. and discusses promising new research areas, which aim to predict PTB through cervical stiffness and elastography measurements, metabolomics, extracellular vesicles and artificial intelligence.

Glycemic control and neonatal outcomes in twin pregnancies with gestational diabetes mellitus

BACKGROUND

Preliminary data suggest that strict glycemic control in twin pregnancies with gestational diabetes mellitus may not improve outcomes but might increase the risk of fetal growth restriction.

OBJECTIVE

This study aimed to investigate the association of maternal glycemic control with the risk of gestational diabetes mellitus-related complications and small for gestational age in twin pregnancies complicated by gestational diabetes mellitus.

STUDY DESIGN

This was a retrospective cohort study of all patients with a twin pregnancy complicated by gestational diabetes mellitus in a single tertiary center between 2011 and 2020, and a matched control group of patients with a twin pregnancy without gestational diabetes mellitus in a 1:3 ratio. The exposure was the level of glycemic control, described as the proportion of fasting, postprandial, and overall glucose values within target. Good glycemic control was defined as a proportion of values within target above the 50th percentile. The first coprimary outcome was a composite variable of neonatal morbidity, defined as at least 1 of the following: birthweight >90th centile for gestational age, hypoglycemia requiring treatment, jaundice requiring phototherapy, birth trauma, or admission to the neonatal intensive care unit at term. A second coprimary outcome was small for gestational age, defined as birthweight <10th centile or <3rd centile for gestational age. Associations between the level of glycemic control and the study outcomes were estimated using logistic regression analysis and were expressed as adjusted odds ratio with 95% confidence interval.

RESULTS

A total of 105 patients with gestational diabetes mellitus in a twin pregnancy met the study criteria. The overall rate of the primary outcome was 32.4% (34/105), and the overall proportion of pregnancies with a small for gestational age newborn at birth was 43.8% (46/105). Good glycemic control was not associated with a reduction in the risk of composite neonatal morbidity when compared with suboptimal glycemic control (32.1% vs 32.7%; adjusted odds ratio, 2.06 [95% confidence interval, 0.77-5.49]). However, good glycemic control was associated with higher odds of small for gestational age compared with nongestational diabetes mellitus pregnancies, especially in the subgroup of diet-treated gestational diabetes mellitus (65.5% vs 34.0%, respectively; adjusted odds ratio, 4.17 [95% confidence interval, 1.74-10.01] for small for gestational age <10th centile; and 24.1% vs 7.0%, respectively; adjusted odds ratio, 3.97 [95% confidence interval, 1.42-11.10] for small for gestational age <3rd centile). In contrast, the rate of small for gestational age in gestational diabetes mellitus pregnancies with suboptimal control was not considerably different when compared with non-gestational diabetes mellitus pregnancies. In addition, in cases of diet-treated gestational diabetes mellitus, good glycemic control was associated with a left-shift of the distribution of birthweight centiles, whereas the distribution of birthweight centiles among gestational diabetes mellitus pregnancies with suboptimal control was similar to that of nongestational diabetes mellitus pregnancies.

CONCLUSION

In patients with gestational diabetes mellitus in a twin pregnancy, good glycemic control is not associated with a reduction in the risk of gestational diabetes mellitus-related complications but may increase the risk of a small for gestational age newborn in the subgroup of patients with mild (diet-treated) gestational diabetes mellitus. These findings further question whether the gestational diabetes mellitus glycemic targets used in singleton pregnancies also apply to twin pregnancies and support the concern that applying the same diagnostic criteria and glycemic targets in twin pregnancies may result in overdiagnosis and overtreatment of gestational diabetes mellitus and potential neonatal harm.

Timing of antenatal corticosteroids in relation to clinical indication

PURPOSE

This study aimed at determining the proportion of women who receive antenatal corticosteroids (ACS) within the optimal time window before birth based on the indication for ACS, and to explore in more detail indications that are associated with suboptimal timing.

METHODS

A retrospective cohort study of all women who received ACS in a single tertiary center between 2014 and 2017. The primary outcome was an ACS-to-birth interval ≤ 7 days. Secondary outcomes were ACS-to-birth interval of ≤ 14 days, and the proportion women who received ACS but ultimately gave birth at term (≥ 37^0/7 weeks). The study outcomes were stratified by the clinical indication for ACS.

RESULTS

A total of 1261 women met the study criteria, of whom 401 (31.8%) and 569 (45.1%) received ACS within ≤ 7 days and ≤ 14 days before birth, respectively, and 203 (16.1%) ultimately gave birth at term. The proportion of women who received ACS within 7 days before birth was highest for women with preeclampsia (50.4%), and was lowest for women with an incidental finding of a short cervix (8.4%). In the subgroup of women with an incidental finding of a short cervix, the likelihood of optimal timing was not related to the magnitude of cervical shortening, history of preterm birth, multifetal gestation, presence of cervical funneling, or the presence of cervical cerclage.

CONCLUSION

Over two-thirds of infants who are exposed to ACS do not get the maximal benefit from this intervention. The current study identified clinical indications for ACS that are associated with suboptimal timing of ACS where more research is needed to develop quantitative, indication-specific prediction models to guide the timing of ACS.

Patterns of discordant growth and adverse neonatal outcomes in twins

BACKGROUND

Intertwin size discordance is an independent risk factor for adverse neonatal outcomes in twin pregnancies. However, size discordance at a given point in gestation fails to take into consideration information, such as the timing of onset and the rate of progression of discordance, that may be of prognostic value.

OBJECTIVE

In this study, we aimed to identify distinct patterns of discordant fetal growth in twin pregnancies and to determine whether these patterns are predictive of adverse pregnancy outcomes.

STUDY DESIGN

This was a retrospective cohort study of women with twin pregnancies in a single tertiary referral center between January 2011 and April 2020, who had at least 3 ultrasound examinations during pregnancy that included assessment of fetal biometry. Size discordance was calculated at each ultrasound examination, and pregnancies were classified into 1 of 4 predetermined patterns based on the timing of onset and the progression of discordance: pattern 1, no significant discordance group (referent); pattern 2, early (<24 weeks' gestation) progressive discordance group; pattern 3, early discordance with plateau group; or pattern 4, late (≥24 weeks' gestation) discordance group. The associations of discordance pattern (using pattern 1 as referent) with preterm birth, preeclampsia, size discordance at birth, and birthweight<10th percentile were expressed as adjusted relative risk with 95% confidence intervals and were compared with those observed for a single measurement of size discordance at 32 weeks' gestation.

RESULTS

Of 2075 women with a twin gestation who were identified during the study period, 1059 met the study criteria. Of the 1059 women, 599 (57%) were classified as no significant discordance (pattern 1), 23 (2%) as early progressive discordance (pattern 2), 160 (15%) as early discordance with plateau (pattern 3), and 277 (26%) as late discordance (pattern 4). The associations of discordance pattern with preterm birth at <34 weeks' gestation and preeclampsia were strongest for pattern 2 (rates of 43% [adjusted relative risk, 3.43; 95% confidence interval, 2.10-5.62] and 17% [adjusted relative risk, 5.81; 95% confidence interval, 2.31-14.60], respectively), intermediate for pattern 3 (rates of 23% [adjusted relative risk, 1.82; 95% confidence interval, 1.28-2.59] and 6% [adjusted relative risk, 2.08; 95% confidence interval, 1.01-4.43], respectively), and weakest for pattern 4 (rates of 12% [adjusted relative risk, 0.96; 95% confidence interval, 0.65-1.42] and 4% [adjusted relative risk, 1.41; 0.68-2.92], respectively). In contrast, a single measurement of size discordance at 32 weeks' gestation showed no association with preeclampsia and only a weak association with preterm birth at <34 weeks' gestation.

CONCLUSION

We identified 4 distinct discordance growth patterns among twins that demonstrated a dose-response relationship with adverse outcomes and seemed to be more informative than a single measurement of size discordance.

Development and external validation of a nomogram for predicting preterm birth at < 32 weeks in twin pregnancy

The purpose of this study was to develop a dynamic model to predict the risk of spontaneous preterm birth at < 32 weeks in twin pregnancy. A retrospective clinical study of consecutively asymptomatic women with twin pregnancies from January 2017 to December 2019 in two tertiary medical centres was performed. Data from one centre were used to construct the model, and data from the other were used to evaluate the model. Data on maternal demographic characteristics, transvaginal cervical length and funnelling during 20-24 weeks were extracted. The prediction model was constructed with independent variables determined by multivariate logistic regression analyses. After applying specified exclusion criteria, an algorithm with maternal and biophysical factors was developed based on 88 twin pregnancies with a preterm birth < 32 weeks and 639 twin pregnancies with a delivery ≥ 32 weeks. It was then evaluated among 34 pregnancies with a preterm birth < 32 weeks and 252 pregnancies with a delivery ≥ 32 weeks in a second tertiary centre without specific training. The model reached a sensitivity of 80.00%, specificity of 88.17%, positive predictive value of 50.33% and negative predictive value of 96.71%; ROC characteristics proved that the model was superior to any single parameter with an AUC of 0.848 (all P < 0.005). We developed and validated a dynamic nomogram model to predict the individual probability of early preterm birth to better represent the complex aetiology of twin pregnancies and hopefully improve the prediction and indication of interventions.

Two-stage nomogram models in mid-gestation for predicting the risk of spontaneous preterm birth in twin pregnancy

PURPOSE

This study aimed to develop two-stage nomogram models to predict individual risk of preterm birth at < 34 weeks of gestation in twin pregnancies by incorporating clinical characteristics at mid-gestation.

METHODS

We used a case-control study design of women with twin pregnancies followed up in a tertiary medical centre from January 2018 to March 2019. Maternal demographic characteristics and transvaginal cervical length data were extracted. The nomogram models were constructed with independent variables determined by multivariate logistic regression analyses. The risk score was calculated based on the nomogram models.

RESULTS

In total, 65 twin preterm birth cases (< 34 weeks) and 244 controls met the inclusion criteria. Based on univariate and multivariate logistic regression analyses, we built two-stage nomogram prediction models with satisfactory discrimination and calibration when applied to the validation sets (first-stage [22-24 weeks] prediction model, C-index: 0.805 and 0.870, respectively; second-stage [26-28 weeks] prediction model, C-index: 0.847 and 0.908, respectively). Restricted cubic splines graphically showed the risk of preterm birth among individuals with increased risk scores. Moreover, the decision curve analysis indicated that both prediction models show positive clinical benefit.

CONCLUSION

We developed and validated two-stage nomogram models at mid-gestation to predict the individual probability of preterm birth at < 34 weeks in twin pregnancy.

Single and repeat cervical-length measurement in twin gestation with threatened preterm labor

OBJECTIVE

To examine the effectiveness of single and repeat sonographic cervical-length (CL) measurement in predicting preterm delivery in symptomatic women with a twin pregnancy.

METHODS

This was a retrospective study of women with a twin gestation who presented with painful and regular uterine contractions at 24 + 0 to 33 + 6 weeks' gestation at the perinatal unit of the University Hospital of Tübingen, Tübingen, Germany between 2012 and 2018. CL was measured on transvaginal ultrasound at the time of admission and a few days later after cessation of contractions. Treatment included administration of tocolytics (usually oral nifedipine), for no more than 48 h, and administration of steroids if CL was ≤ 25 mm. Patients were clustered into five groups according to the CL measurement obtained at first assessment: < 10.0 mm; between 10.0 and 14.9 mm; between 15.0 and 19.9 mm; between 20.0 and 24.9 mm; and ≥ 25.0 mm. For each group, we calculated the test performance of CL measurement for prediction of preterm delivery within the subsequent 7 days and before 34 weeks' gestation. Regression analysis was used to evaluate the test performance of the second CL measurement for predicting preterm delivery within 7 days after the second assessment.

RESULTS

The study population consisted of 257 twin pregnancies, of which 80.2% were dichorionic diamniotic. Median maternal and gestational ages at the time of admission were 32.0 years and 29.9 weeks' gestation, respectively. Preterm birth within 7 days of admission occurred in 23 (8.9%) pregnancies, and 82 (31.9%) patients delivered prior to 34 weeks' gestation. Median CL for the entire study population was 17.0 mm. Delivery within 7 days after the first assessment occurred in 29.0%, 10.6%, 4.2%, 6.3% and 0% of women with CL < 10.0 mm, 10.0-14.9 mm, 15.0-19.9 mm, 20.0-24.9 mm and ≥ 25.0 mm, respectively. There was a weak, but significant, association between the CL measurement at the time of admission and the time interval between admission and delivery (interval = 27.9 + 0.58 × CL; P = 0.003, r = 0.184). CL was measured again after a median time interval of 3 (interquartile range (IQR), 2-5) days in 248 cases. Median second CL measurement was 17.0 (IQR, 11.5-22.0) mm. Delivery occurred within the subsequent 7 days after the second measurement in 25/248 (10.1%) cases. Binary regression analysis indicated that the first (odds ratio (OR), 0.895; P = 0.003) and second (OR, 0.908; P = 0.002) CL measurements, but not the difference between the two measurements (OR, 0.961; P = 0.361), were associated significantly with delivery within 7 days after the second measurement. Receiver-operating-characteristics (ROC)-curve analysis for the prediction of delivery within 7 days after the second assessment did not show a significant difference between the predictive performance of the first (area under ROC curve (AUC), 0.676 (95% CI, 0.559-0.793)) and the second (AUC, 0.661 (95% CI, 0.531-0.790)) measurement.

CONCLUSION

Sonographic measurement of CL can be helpful in predicting preterm delivery within 7 days of presentation in symptomatic women with a twin gestation; however, the test performance is relatively weak. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Additional benefits of three-dimensional ultrasound for prenatal assessment of twins

Three-dimensional ultrasound (3DUS) may provide additional information for prenatal assessment of twins. It may improve the diagnostic confidence of dating, nuchal translucency (NT) and chorionicity assignment in twin pregnancies. The "virtual 3DUS placentoscopy" can guide selective fetoscopic laser photocoagulation (SFLP) to treat twin-twin transfusion syndrome (TTTS). Volumetric assessment of the dysmorphic acardiac twin with the Virtual Organ Computer-aided Analysis (VOCAL) software is more accurate than the conventional ultrasound measurement. Twin anemia polycythemia (TAP) sequence and selective intrauterine growth restriction (sIUGR) may be clinically monitored with 3DUS placental volume (PV) and power Doppler vascular indices. Congenital anomalies are more common in twins. Evaluation of fetal anomalies with 3DUS could assist perinatal management. The 3DUS power Doppler can provide a better understanding of true and false umbilical cord knots, which are commonly found in monoamniotic (MA) twins. Single demise in monochorionic (MC) twin pregnancies can cause severe neurologic morbidity in the surviving co-twin. Prenatal prediction of brain injury in the surviving co-twin with unremarkable neurosonographic examination is difficult. The 3DUS power Doppler may aid in prenatal detection of subtle abnormal cerebral perfusion. Prenatal assessment of conjoined twins with 3DUS is important if emergency postnatal surgical separation is anticipated. There is no significant additional advantage in using real-time 3DUS to guide prenatal interventions. Assessment of the cervix and pelvic floor during twin pregnancies is enhanced with 3DUS. Due to lack of high-quality studies, routine prenatal 3DUS in twin pregnancies needs to be balanced with risks of excessive ultrasound exposure.

Efficacy of allylestrenol combined with ritodrine on threatened premature labor and its influence on inflammatory factors in peripheral blood

Efficacy of allylestrenol combined with ritodrine on threatened premature labor (TPTL) and its influence on inflammatory factors in peripheral blood were investigated. A total of 206 cases of TPTL patients from 2014 to 2016 were collected in Zhongshan Hospital Affiliated to Fudan University, and 106 cases were treated with allylestrenol combined with ritodrine as a research group and 100 cases were treated with allylestrenol combined with magnesium sulfate as a control group. General information of patients was collected, and changes in the expression levels of IL-17, IL-10 and IL-6 were detected by enzyme-linked immunosorbent assay. Prolonged pregnancy time, success rate of fetal protection and average delivery time of patients were recorded. The adverse pregnancy conditions were compared, including the Apgar score of newborns, birth weight and adverse conditions, and postpartum hemorrhage volume and postpartum hospital stays in the two groups were recorded. Prolonged pregnancy time, success rate of fetal protection and average delivery time in the research group were significantly higher than those in the control group (P<0.05). After treatment, the levels of IL-17, IL-10 and IL-6 in serum of the two groups were significantly lower than those before treatment (P<0.05), and were significantly lower in the research group than in the control group (P<0.05). The average neonatal weight and Apgar score in the research group were significantly better than those in the control group (P<0.05). Postpartum hemorrhage, postpartum hospital stays and incidence rate of toxic side effects, neonatal death, malformation and asphyxia in the research group were significantly lower than those in the control group (P<0.05). Allylestrenol combined with ritodrine can significantly reduce the expression levels of IL-17, IL-10 and IL-6 in TPTL, reduce adverse pregnancy conditions, prolong gestational weeks, and has higher safety and better application value.

Cervical pessary for preventing preterm birth in twin pregnancies with maternal short cervix after an episode of threatened preterm labor: randomised controlled trial

BACKGROUND

No intervention has proved effective to date in reducing the spontaneous preterm birth rate in twin pregnancies following an episode of threatened preterm labor and with a short cervix remaining. This study was designed to ascertain whether cervical pessaries are useful in preventing spontaneous preterm birth in women with twin pregnancies and a short cervix remaining after a threatened preterm labor episode.

STUDY DESIGN

This open, randomized, controlled trial was conducted in 132 pregnant women who had not delivered 48 hours after a threatened preterm labor episode and had a short cervix remaining (≤20 mm between 24⁰ and 29⁶ weeks and ≤10 mm between 30⁰ and 33⁶ weeks). Patients were randomly assigned to cervical pessary (n = 67) or routine management (n = 65). The primary outcome was the spontaneous preterm birth rate before 34 weeks. Spontaneous preterm birth before 28 and 37 weeks and neonatal morbidity and mortality were also evaluated in an intention-to-treat analysis.

RESULTS

Significant differences were observed in the spontaneous preterm birth rate before 34 weeks between the pessary and routine management groups (11 of 67 [16.4%] in the pessary group vs 21 of 65 [32.3%] in the control group; relative risk, 0.51 [confidence interval, 0.27-0.97]; P = .03). No significant differences were observed in the preterm birth rate < 28 weeks or < 37 weeks between groups. The pessary group less frequently required readmission for new threatened preterm labor episodes (4 of 67 [5.6%] vs 14 of 65 [21.5%]; relative risk, 0.28 [confidence interval, 0.10-0.80]; P = .009). Significant reduction was observed in the number of neonates weighing less than 2500 g (17.9% [24 of 134] vs 70.8% [92 of 130]; relative risk, 0.25 [confidence interval, 0.15-0.43]; P < .0001).

CONCLUSION

Pessary use did significantly lower the spontaneous preterm birth rate before 34 weeks in twin pregnancies with maternal short cervix remaining after a threatened preterm labor episode. Pessary use also reduced the threatened preterm labor recurrence and neonates' weight less than 2500 g.

Quantitative fetal fibronectin to predict spontaneous preterm delivery after laser surgery for twin-twin transfusion syndrome

Our goal was to assess whether quantitative fetal fibronectin (qfFN) is associated with spontaneous preterm birth (sPTB) after laser surgery for twin-twin transfusion syndrome (TTTS). qfFN was collected within 24 hours before and after laser surgery. Aims were: (1) To determine if qfFN changed with operative fetoscopy; and (2) To estimate the number of patients needed to study the predictive value of qfFN for sPTB <28 and <32 weeks. Results are reported as median (range). Among 49 patients, there was no net difference in qfFN levels after laser surgery [0.0 ng/mL (-37 to +400), p = 0.6041]. However, patients with a qfFN increase >10 ng/mL were 19 times more likely to undergo sPTB at <28 weeks (OR = 19.5). We determined that 383 and 160 patients would be needed to achieve adequate statistical power for qfFN to be predictive of sPTB at a GA <28 weeks and <32 weeks, respectively. In conclusion, laser surgery did not alter the qfFN level within the entire cohort, but qfFN may be useful in identifying a subset of patients at increased risk of preterm delivery.

The greater risk of preterm birth in triplets is mirrored by a more rapid cervical shortening along gestation

BACKGROUND

The risk of preterm birth increases with plurality. However, data are limited about the role of cervical length in triplet pregnancies and how the greater predisposition for preterm birth in triplet pregnancies, compared with twin pregnancies, is reflected by cervical length. Specifically, it is unclear whether the greater predisposition of triplet pregnancies for preterm birth is reflected by a more rapid cervical shortening during gestation compared with twin pregnancies (and therefore a shorter cervical length at any given gestational age), by a greater risk for preterm birth per given cervical length at any given gestational age, or both.

OBJECTIVE

The purpose of the study was to compare the rate of cervical shortening during gestation and the correlation between cervical length and gestational age at birth in asymptomatic women with triplet vs twin pregnancies.

STUDY DESIGN

This was a retrospective study of women with triplet or twin pregnancies who were who were observed in a tertiary center who underwent serial sonographic measurement of cervical length from 16-32 weeks gestation. Change in cervical length during gestation and relationship of cervical length with gestational age at birth were compared between the triplets and twins groups.

RESULTS

A total of 431 measurements of cervical length from 86 women with triplets was analyzed and compared with 2826 measurements of cervical length from 441 women with twins. The rate of cervical shortening among triplet pregnancies was higher than among twin pregnancies starting from 18 weeks of gestation (slope of regression line, -1.297 vs -0.907; P < .001). Similarly, the proportion of women with cervical length of <25 mm or 15 mm was higher among triplet pregnancies than among twin pregnancies (34.0% vs 21.0% [P < .001] and 16.7% vs 8.4% [P = .001]), respectively. For any given cervical length measured after 22 weeks of gestation, the associated gestational length at birth in triplet pregnancies was lower by 2.7 weeks on average compared with twin pregnancies (P < .001).

CONCLUSION

The higher rate of preterm birth in triplet pregnancies, compared with twin pregnancies, is reflected by both a more rapid cervical shortening during gestation and a lower gestational age at birth per any given cervical length.

The use of sonographic cervical length assessment for the prediction of time from induction to delivery

OBJECTIVE

The objective of this study is to investigate the role of trans-vaginal cervical length measurement in the prediction of the interval to successful vaginal delivery after induction of labor with balloon catheter.

METHODS

In this prospective study of cervical length measurement before induction of labor, singleton pregnancies that underwent induction of labor between 37 and 42 weeks of gestation were included. The data collected included trans-vaginal sonographic cervical measurements followed by digital cervical assessment. Bishop score was used to quantify digital assessment (before induction of labor).

RESULTS

During the study period, 71 patients were included in the study. A statistically significant linear correlation was found between sonographic cervical length prior to induction of labor and the time of delivery (Pearson correlation 0.335; p values 0.005). Of the 57 vaginal deliveries, 27 patients had a cervical length of less than 28 mm. Patients with a cervical length of less than 28 mm had a significantly shorter time to delivery compared to patients with more than 28 mm length (20.4 versus 28.7, respectively; p value = 0.019). Cervical length of 28 mm remained significantly correlated even after performing several logistic regression models in order to control for confounders such as parity and age. In addition, a correlation was found between Bishop scores of above 7 to the time to delivery.

CONCLUSIONS

Cervical length is correlated linearly to the time interval between induction of labor and delivery. A cervical length of less than 28 mm was found to be statistically significant in predicting a shorter time to delivery.