Spontaneous Preterm Birth in Multiples

The Use of Mid-Pregnancy Cervical Length to Predict Preterm Birth in Brazilian Asymptomatic Twin Gestations

OBJECTIVE

 To describe a reference curve for cervical length (CL) in mid-trimester twin gestations using transvaginal ultrasound (TVU) and to investigate whether short CL increases spontaneous preterm birth (sPTB) in asymptomatic twin pregnancies.

METHODS

 This was a prospective cohort study performed at 17 outpatient antenatal facilities of Brazil with women at 18 0/7 to 22 6/7 weeks of gestation who participated in a randomized clinical trial screening phase (P5 trial) between July 2015 and March 2019. TVU was performed to provide CL measurement in all screened women. Almost all women with CL ≤ 30 mm received vaginal progesterone 200mg/day and they were also randomized to receive cervical pessary or not. We considered data from the CL distribution among asymptomatic twin pregnancies and analyzed CL and its association with PTB generating receiver operating characteristics (ROC) curves and Kaplan-Meier curves.

RESULTS

 A total of 253 pregnant women with twins were included in the distribution curve. The mean CL was 33.7 mm and median was 35.5mm. The 10th percentile was 17.8mm. We identified a PTB rate of 73.9% (187/253) with 33.6% of sPTB < 37 (85/253) and 15% (38/253) of sPTB < 34 weeks. The best cutoff point to predict sPTB < 37 was 24.15 mm. However, the ROC curve showed a poor performance (0.64). The Kaplan-Meier survival curves identified that only CL values ≤ 20mm were associated to sPTB < 34 weeks.

CONCLUSION

 A cutoff point of CL ≤ 20 mm can be interesting point to identify short cervix in Brazilian twin pregnancies. However, in Brazilian asymptomatic twin pregnancies, CL does not show a good performance to predict PTB.

Latency to delivery in physical examination-indicated cerclage in twins is similar to that in singleton pregnancies

OBJECTIVE

To compare latency to delivery and perinatal outcomes between twin and singleton pregnancies undergoing physical examination-indicated cerclage.

METHODS

Retrospective observational study (2007-2017) of women who underwent physical examination-indicated cerclage at the Hospital Clinic of Barcelona. Primary outcomes were latency from cerclage to delivery and gestational age at delivery. Secondary outcomes included: neonatal morbidity and mortality, preterm prelabor rupture of membranes, clinical chorioamnionitis and cerclage displacement. Wilcoxon-test and χ² test were used to compare continuous and categorical variables.

RESULTS

Sixty women were included (17 twins and 43 singletons). There were no differences in gestational age at cerclage or presence of bulging membranes between groups. Median (25th;75th percentile) gestational age at delivery was 27.1 (24.5;32.3) weeks in the twin group and 27.6 (25.3;35.3) weeks in the singleton group (P = 0.594). There were no statistically significant differences in latency from cervical cerclage to delivery between the two groups (43 days [21;64] vs. 29 days [16;76], respectively; P = 0.938). There were no differences in neonatal mortality (2/26 [7.7%] vs. 1/33 [3.1%]; P = 0.578) or in composite neonatal morbidity (14 [53.9%] vs. 14 [42.4%]; P = 0.283) between groups, respectively.

CONCLUSION

These results suggest that physical examination-indicated cerclage placement in twins could prolong latency to delivery similarly to singleton pregnancies.

Effects of vaginal microbiota and cervical cerclage on obstetric outcomes of twin pregnancies with cervical incompetence: a retrospective study

PURPOSE

To determine the role of vaginal microbiota in the efficacy of cervical cerclage in obstetric outcomes of twin pregnancies.

METHODS

This retrospective study enrolled 68 twin pregnant women diagnosed with cervical incompetence (CIC) and 68 twin pregnancies without CIC. The CIC group was further divided into two subgroups: cerclage group (n = 51) and non-cerclage group (n = 17), according to whether cervical cerclage was performed in the second trimester. Data of vaginal microbiota and obstetric outcomes were collected and compared.

RESULTS

Cervical incompetence had harmful effect on both pregnancy outcomes and vaginal microecology, characterized by earlier gestational week at delivery (30.3 ± 5.6 vs 35.6 ± 1.1, P < 0.001), a lower birth weight of newborns (OR 0.40; 95% CI 0.22-0.74), a higher vaginal pH value (OR 0.11; 95% CI 0.04-0.30) and a lower abundance of Lactobacillus (OR 0.34; 95% CI 0.17-0.70). In addition, compared with the vaginal microbiota after cerclage, less normal diversity of bacterial flora (OR 0.35; 95% CI 0.12-1.01), less Lactobacillus (OR 0.40; 95% CI 0.18-0.91) and more Gardnerella vaginalis (OR 18.92; 95% CI 2.38-150.35) appeared before cerclage. Besides, the unhealthy vaginal environment also had an unfavorable influence on the neonatal outcomes, increased neonatal mortality rate was observed in the group of vaginal pH > 4.5 (P < 0.05). Fortunately, compared with the non-cerclage group, the cerclage group had a longer interval from diagnosis to delivery (≥ 8 weeks) and more of the newborns' birth weight were not less than 1500 g (P < 0.05).

CONCLUSION

A healthy vaginal environment is essential to improve the obstetric outcome for twin pregnancies with cervical cerclage.

Tools, techniques, and future opportunities for characterizing the mechanobiology of uterine myometrium

The myometrium is the smooth muscle layer of the uterus that generates the contractions that drive processes such as menstruation and childbirth. Aberrant contractions of the myometrium can result in preterm birth, insufficient progression of labor, or other difficulties that can lead to maternal or fetal complications or even death. To investigate the underlying mechanisms of these conditions, the most common model systems have conventionally been animal models and human tissue strips, which have limitations mostly related to relevance and scalability, respectively. Myometrial smooth muscle cells have also been isolated from patient biopsies and cultured in vitro as a more controlled experimental system. However, in vitro approaches have focused primarily on measuring the effects of biochemical stimuli and neglected biomechanical stimuli, despite the extensive evidence indicating that remodeling of tissue rigidity or excessive strain is associated with uterine disorders. In this review, we first describe the existing approaches for modeling human myometrium with animal models and human tissue strips and compare their advantages and disadvantages. Next, we introduce existing in vitro techniques and assays for assessing contractility and summarize their applications in elucidating the role of biochemical or biomechanical stimuli on human myometrium. Finally, we conclude by proposing the translation of "organ on chip" approaches to myometrial smooth muscle cells as new paradigms for establishing their fundamental mechanobiology and to serve as next-generation platforms for drug development.

Efficacy of physical examination-indicated cerclage in twin pregnancies compared with singleton pregnancies: a systematic review and meta-analysis

INTRODUCTION

To compare the pregnancy outcomes of physical examination-indicated cerclage (PEIC) between twin and singleton pregnancies with acute cervical insufficiency.

EVIDENCE ACQUISITION

We searched Medline, Ovid, Scopus, EBSCO, ClinicalTrials.gov and the Cochrane Central Register of Controlled Trials from their commencement until Dec 2019 for relevant studies. Patient-level data abstraction and analysis were done by two independent authors.

EVIDENCE SYNTHESIS

A total of five studies with 786 women were included in the final analysis. The pooled outcomes showed that PEIC was associated with a similar reduction in preterm birth (PTB) at <32 (Risk ratio [RR] 0.93, 95% CI 0.79-1.11, I²⁼0%, P=0.43), and 28 (RR 1.03, 95% CI 0.82-1.29, I²⁼0%, P=0.81) weeks of gestation; however, a much higher frequency of PTB was observed at <36 (RR 0.74, 95% CI 0.66-0.83, I²⁼0%, P<0.000), and 34 (RR 0.80, 95% CI 0.68-0.93, I²⁼0%, P=0.004) weeks of gestation in twin pregnancies than in singleton pregnancies. No significant differences in perinatal outcomes, including neonatal death (RR 1.03, 95% CI 0.64-1.67, I²⁼52%, P=0.900), stillbirth (RR 0.73, 95% CI 0.37-1.44, I²=0%, P=0.360), perinatal mortality (RR 0.94, 95% CI 0.65-1.38, P=0.760) and neonatal complications were found between twin and singleton pregnancies.

CONCLUSIONS

Our meta-analysis indicated that PEIC achieved good perinatal prognosis in both singleton and twin pregnancies. However, because the available evidence is insufficient to attain a strong conclusion, so further high-quality trials are needed to confirm our findings.

Impact of mode of delivery on perinatal outcome in moderately and late preterm twin birth

OBJECTIVE

To examine the impact of the mode of delivery on neonatal and maternal outcomes in moderately and late preterm twin birth.

METHODS

This single-center cohort study included 275 live diamniotic moderately and late preterm twin deliveries at 32⁺⁰ -36⁺⁶  weeks of gestation. These twin deliveries were divided into two groups according to the planned mode of delivery: trial of labor (TOL) (N=199, 72.4%) and planned cesarean section (CS) (N=76, 27.6%). The primary outcome was neonatal morbidity. Maternal outcome and the effects of gestational age and chorionicity on neonatal outcome were also studied.

RESULTS

Of the women in the TOL group, 170 (85.4%) delivered vaginally. Both for the first and second twin, and for dichorionic or monochorionic deliveries, there were no differences between the TOL and CS groups in composite neonatal morbidity or in other neonatal outcomes. No significant differences were found between the TOL and CS groups when the moderately and late preterm gestational age cohorts were studied separately. Mothers in the planned CS group more often had puerperal infection and surgical complications in comparison with mothers in the TOL group.

CONCLUSION

Among 275 moderately and late preterm twin deliveries, planned mode of delivery did not affect neonatal outcome.

The role of extracellular matrix in normal and pathological pregnancy: Future applications of microphysiological systems in reproductive medicine

IMPACT STATEMENT

Extracellular matrix in the womb regulates the initiation, progression, and completion of a healthy pregnancy. The composition and physical properties of extracellular matrix in the uterus and at the maternal-fetal interface are remodeled at each gestational stage, while maladaptive matrix remodeling results in obstetric disease. As in vitro models of uterine and placental tissues, including micro-and milli-scale versions of these organs on chips, are developed to overcome the inherent limitations of studying human development in vivo, we can isolate the influence of cellular and extracellular components in healthy and pathological pregnancies. By understanding and recreating key aspects of the extracellular microenvironment at the maternal-fetal interface, we can engineer microphysiological systems to improve assisted reproduction, obstetric disease treatment, and prenatal drug safety.

Comparison of the myometrial transcriptome from singleton and twin pregnancies by RNA-Seq

Preterm birth is recognized as the primary cause of infant mortality worldwide. Twin pregnancies are significantly more at risk of preterm birth than singleton pregnancies. A greater understanding of why this is and better modes of treatment and prevention are needed. Key to this is determining the differing pathophysiological mechanisms of preterm birth in twins, including the role of the myometrium and premature uterine contraction. We performed RNA sequencing (RNA-Seq) of human myometrium from singleton and twin pregnancies at term (> 37+0 weeks) and preterm (< 37+0 weeks), collected during pre-labour Caesarean Section. RNA-Seq libraries were prepared from polyA-selected RNA and sequenced on the Illumina HiSeq 4000 platform. Differentially expressed genes (DEGs), GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment were conducted using R software. Significance was determined with a false discovery rate-adjusted P value of <0.05. Only 3 DEGs were identified between gestational age-matched singleton and twin myometrium and only 1 DEG identified between singleton term and twin preterm tissues. Comparison of singleton preterm myometrium with twin term myometrium however, revealed 75 down-regulated and 24 up-regulated genes in twin myometrium. This included genes associated with inflammation and immune response, T cell maturation and differentiation and steroid biosynthesis. GO and KEGG enrichment analyses for biologically relevant processes and functions also revealed several terms related to inflammation and immune response, as well as cytokine-cytokine receptor interaction and chemokine receptor signalling. Data indicate that little or no differences exist in the transcriptome of singleton and twin myometrium when matched for gestational age. The significant up- and down-regulation of genes identified between preterm singleton and twin myometrium at term may point to transcriptome changes associated with the chronic levels of uterine stretch in twin pregnancy or genes associated with the myometrium transitioning to labour onset.

Use of progesterone supplement therapy for prevention of preterm birth: review of literatures

Preterm birth (PTB) is one of the most common complications during pregnancy and it primarily accounts for neonatal mortality and numerous morbidities including long-term sequelae including cerebral palsy and developmental disability. The most effective treatment of PTB is prediction and prevention of its risks. Risk factors of PTB include history of PTB, short cervical length (CL), multiple pregnancies, ethnicity, smoking, uterine anomaly and history of curettage or cervical conization. Among these risk factors, history of PTB, and short CL are the most important predictive factors. Progesterone supplement therapy is one of the few proven effective methods to prevent PTB in women with history of spontaneous PTB and in women with short CL. There are 2 types of progesterone therapy currently used for prevention of PTB: weekly intramuscular injection of 17-alpha hydroxyprogesterone caproate and daily administration of natural micronized progesterone vaginal gel, vaginal suppository, or oral capsule. However, the efficacy of progesterone therapy to prevent PTB may vary depending on the administration route, form, dose of progesterone and indications for the treatment. This review aims to summarize the efficacy and safety of progesterone supplement therapy on prevention of PTB according to different indication, type, route, and dose of progesterone, based on the results of recent randomized trials and meta-analysis.

Hematological disorders at birth in complicated monochorionic twins

INTRODUCTION

Monochorionic twins are at risk of severe complications including twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS) and acute peripartum TTTS. The pathophysiology is based on inter-twin blood transfusion through placental vascular anastomoses. Areas covered: This review focuses on the incidence, management and outcome of neonatal hematological complications at birth in TTTS, TAPS and acute peripartum TTTS. Expert commentary: Hematological disorders are often present at birth in monochorionic twins and include acute or chronic anemia, polycythemia and thrombocytopenia. Routine measurement of complete blood counts in all complicated monochorionic twins is strongly recommended. Increased awareness on these disorders and correct diagnostic tests will lead to prompt and adequate management at birth.