Placental Anatomy and Function in Twin Gestations

Placental architectural characteristics following laser ablation within monochorionic twins complicated by twin-twin transfusion syndrome: A systematic review and meta-analysis of outcomes

INTRODUCTION

Twin-twin transfusion syndrome (TTTS) complicates approximately 10%-15% of all monochorionic twin pregnancies. The aim of this review was to evaluate the placental architectural characteristics within TTTS twins following laser and elucidate their impact on fetal outcomes and operative success.

MATERIAL AND METHODS

Five databases were searched from inception to August 2023. Studies detailing post-delivery placental analysis within TTTS twins post-laser were included. Studies were categorized into two main groups: (1) residual anastomoses following laser and (2) abnormal cord insertion: either velamentous and/or marginal or proximate. The primary outcome was to determine the proportion of TTTS placentas with residual anastomoses and abnormal cord insertions post-laser. Secondary outcomes included assessing residual anastomoses on post-laser fetal outcomes and assessing the relationship between abnormal cord insertion and TTTS development. Study bias was critiqued using the Joanna Briggs Institute checklists and Cochrane risk of bias tool. Random-effects meta-analysis was used, and results were reported as pooled proportions or odds ratio (OR) with 95% confidence interval (CI). PROSPERO registration: CRD42023476875.

RESULTS

Twenty-six studies, comprising 4013 monochorionic twins, were included for analysis. The proportion of TTTS placentas with residual anastomoses following laser was 24% (95% CI, 0.12-0.41), with a mean and standard deviation of 4.03 ± 2.95 anastomoses per placenta. Post-laser residual anastomoses were significantly associated with intrauterine fetal death (OR, 2.38 [95% CI, 1.33-4.26]), neonatal death (OR, 3.37 [95% CI, 1.65-6.88]), recurrent TTTS (OR, 24.33 [95% CI, 6.64-89.12]), and twin anemia polycythemia sequence (OR, 13.54 [95% CI, 6.36-28.85]). Combined abnormal cord (velamentous and marginal), velamentous cord, and marginal cord insertions within one or both twins following laser were reported at rates of 49% (95% CI, 0.39-0.59), 27% (95% CI, 0.18-0.38), and 28% (95% CI, 0.21-0.36), respectively. Combined, velamentous and marginal cord insertions were not significantly associated with TTTS twins requiring laser (p = 0.72, p = 0.38, and p = 0.71, respectively) vs non-TTTS monochorionic twins.

CONCLUSIONS

To the best of our knowledge, this is the first review to conjointly explore outcomes of residual anastomoses and abnormal cord insertions within TTTS twins following laser. A large prospective study is necessitated to assess the relationship between abnormal cord insertion and residual anastomoses development post-laser.

Retrospective comparison of monochorionic diamniotic twin pregnancies stratified by spontaneous or artificial conception

OBJECTIVES

To compare outcomes of monochorionic diamniotic (MCDA) twin pregnancies by in vitro fertilization (IVF) vs. spontaneously conceived counterparts.

METHODS

Retrospective comparison. Data about MCDA twin pregnancies, conceived spontaneously or by IVF, attending the Twin Pregnancy Care Unit of Sant'Anna Hospital in Turin (Italy) between January 1st 2010 and March 31st 2022, were collected retrospectively. Obstetric, fetal, and neonatal outcomes of MCDA twin pregnancies by IVF were compared to those of spontaneously conceived counterparts. Data were described by univariate and multivariate analysis.

RESULTS

541 MCDA twin pregnancies were included in the study, among which 45 conceived by IVF and 496 spontaneously conceived. Women with IVF twins were older than those who conceived spontaneously (36.7 ± 5.7 vs. 32.1 ± 5.2 years; p<0.001). No significant difference in the prevalence of pregnancy complications between the two groups was found, except for an increased incidence of hypertensive disorders among IVF pregnancies (17.8 vs. 8.5 %; p=0.039), which resulted nonsignificant after adjusting for maternal age and parity (aOR 1.9, 95 % CI 0.8-4.6). Data about 1,046 live born babies (90 conceived by IVF and 956 spontaneously) were also collected: perinatal outcomes did not differ between the two groups.

CONCLUSIONS

Our results suggest that MCDA twin pregnancies following IVF are not at increased risk of adverse outcomes compared to spontaneous MCDA twin pregnancies.

Effect of fetoscopic laser surgery on the placental characteristics and birth-weight discordance of twins with twin-to-twin transfusion syndrome

Objective

This study explored the effect of fetoscopic laser surgery on the placental structure and birth-weight discordance of twin-to-twin transfusion syndrome (TTTS).

Methods

A retrospective cohort study was conducted in TTTS patients who were admitted to the Peking University Third Hospital between April 2014 and April 2020. The patients were divided into two groups: laser group and control group. Placentas with twin survival were injected, and pregnancy outcomes and placental characteristics of the two groups were compared. The correlation between the birth-weight discordance and placental characteristics in each group was analyzed.

Results

The gestational age at first diagnosis in the laser group was significantly smaller than that in the control group (21.6 ± 2.8 weeks vs. 27.7 ± 3.0 weeks, p < 0.001). The proportion of patients with TTTS stage-I in the laser group was significantly lower than the control group (9.4 vs. 64.0%, p < 0.001). The gestational age at delivery in the laser group was significantly larger than that in the control group (33.6 ± 2.1 weeks vs. 31.4 ± 2.5 weeks, p = 0.001). In the laser group, the birth-weight discordance ratio was positively correlated with the placental territory discordance ratio (Spearman coefficient = 0.556; p = 0.001).

Conclusion

The birth-weight discordance is positively correlated with placental territory discordance in TTTS patients after FLS.

A study on the correlation of placental characteristics and the onset of selective intrauterine growth restriction

OBJECTIVE

To investigate the correlation between placental characteristics and the onset of selective intrauterine growth restriction (sIUGR) and to explore the influence of placental characteristics on sIUGR onset.

METHODS

A retrospective cohort study was conducted at our hospital from April 2013 to April 2019. The pregnancy data and placental perfusion of 114 sIUGR patients who had received conservative treatment and delivered in our hospital were included. Correlation analysis was conducted between the total diameter of placental anastomoses, placental territory discordance, umbilical cord insertion point distance ratio, and the onset time of sIUGR.

RESULTS

The prevalence of AA anastomoses was 88.6% (101/114), with an average total diameter of 2.8  ±  1.5 mm, the prevalence of AV anastomoses was 93.9% (107/114), with an average diameter of 5.4  ±  3.6 mm, and the prevalence of VV anastomoses was 18.4% (21/114), with an average diameter of 4.0  ±  1.9 mm. There was a significant negative correlation between the time of sIUGR onset and the placental territory discordance ratio with a Spearman correlation coefficient of -0.306 (P  =  0.001).

CONCLUSIONS

The larger the placental territory discordance, the earlier onset time of sIUGR.

Comparison of the ratio of placental territory discordance to birthweight discordance in placentas of monochorionic diamniotic twins

The ratio of placental territory discordance to birthweight discordance was calculated in monochorionic diamniotic twin placentas. We then determined whether the ratio: (1) correlated with the overall diameter of the placental superficial vascular anastomoses and (2) was different in normal monochorionic diamniotic twin (normal MCDA), twin-to-twin transfusion syndrome (TTTS), and selective intrauterine growth restriction (sIUGR) pregnancies. A prospective study of MCDA placentas was conducted from April 1, 2016, to April 1, 2019, including three groups, normal MCDA (N = 49), TTTS (N = 38), and sIUGR (N = 52). Placentas were studied via dye injection. In the normal MCDA, sIUGR, and TTTS groups, the ratio positively correlated with the overall diameter of the placental superficial vascular anastomoses (Spearman's = 0.295, 0.619, and 0.530; p = 0.040, <0.001, and 0.001, respectively) and gradually decreased from normal MCDA to sIUGR and to TTTS (2.88 (0.34, 64.25), 1.70 (0.27, 4.52), and 1.03 (0.12, 15.17); p < 0.001, p = 0.016/<0.001/0.005, respectively). The placental territory discordance to birthweight discordance ratio is an effective index reflecting the overall vascular anastomoses in MCDA placentas.

Comparison of placental characteristics of twin-twin transfusion syndrome with and without selective intrauterine growth restriction

OBJECTIVE

To explore differences among placental anastomoses, territory discordance, and umbilical cord insertion of twin-to-twin transfusion syndrome (TTTS) with and without selective intrauterine growth restriction (sIUGR).

METHODS

This study retrospectively analyzed 57 patients with TTTS who received conservative treatment and finally delivered at the Department of Obstetrics and Gynecology of Peking University Third Hospital from April 2014 to April 2019. Nine of the patient's placentas were too broken to finish the perfusion, and 48 were kept for graph analysis after perfusion. Among the 48 placentas, there were 17 in the TTTS with sIUGR group and 31 in the TTTS without sIUGR group. Differences in the placentas were compared between groups.

RESULTS

The birth weight discordance ratio in the sIUGR group was significantly higher than that in the non-sIUGR group (0.41 ± 0.20 vs 0.24 ± 0.15, p = .001). The prevalence of thick artery-artery (AA) anastomoses in the sIUGR group was significantly higher than that in the non-sIUGR group (35.3% vs 6.5%, p = .017). The placental territory discordance ratio in the sIUGR group was significantly higher than that in the non-sIUGR group (0.40 [0.05, 0.86] vs 0.25 [0.02, 0.67], p = .024). The prevalence of velamentous cord insertion in the sIUGR group was significantly higher than that in the non sIUGR group (35.3% and 6.5%, p = .017).

CONCLUSIONS

Placental territory discordance and velamentous umbilical cord insertion may be causes of TTTS with sIUGR. Compared with TTTS without sIUGR, TTTS with sIUGR had a higher prevalence of protective AA anastomoses in the placenta.