Perinatal Outcome, Placental Pathology, and Severity of Discordance in Monochorionic and Dichorionic Twins

The Role of Chorionicity in Placenta-Related Disorders

INTRODUCTION

Twin pregnancy is associated with higher rates of maternal morbidities including gestational diabetes and hypertension. Dichorionic twins are believed to have greater placental mass. Our objective was to study the incidence of two placenta-related disorders: gestational diabetes and hypertension, in dichorionic versus monochorionic twin pregnancies.

METHODS

Patients' data of all consecutive twin pregnancies over a period of 12 years were collected from medical records. Data on chorionicity were retrieved from 1st trimester ultrasound reports. Maternal complications including gestational hypertension and diabetes were collected, and incidence was compared between dichorionic and monochorionic twin pregnancies. Records lacking chorionicity data and cases with pregestational diabetes were excluded.

RESULTS

A total of 960 twin pregnancies, 121 monochorionic and 839 dichorionic, were included. Average maternal age did not differ significantly between the groups. The median gestational age at delivery was 36.0 weeks in monochorionic and 36.7 in dichorionic twins. Primiparity (40.4% vs. 23.1%, p < 0.001) and the rate of infertility treatments (51.5% vs. 7.4%, p < 0.001) were both more common in the dichorionic group. The incidence of gestational hypertension disorders was 14% in monochorionic versus 11% in dichorionic twins (p = 0.36). Gestational diabetes was more common in dichorionic compared to monochorionic twins (9.4% and 2.5%, respectively); however, logistic multivariate analysis showed that gestational diabetes was highly correlated with maternal age (p < 0.001) and infertility treatments (p < 0.001) but not with chorionicity (p = 0.136).

CONCLUSION

Our results may imply that greater placental mass does not increase the risk for gestational hypertension and diabetes. This might support the role of additional multiple maternal factors associated with these complications.

The prognostic role of CRL discordance in first trimester ultrasound

OBJECTIVES

In the first trimester, intertwin crown-rump length (CRL) discordance has emerged as a notable factor linked to adverse perinatal health effects. It is frequently employed as a basis for counseling parents regarding potential adverse pregnancy outcomes. Despite its established association with adverse outcomes, the significance of CRL discordance in substantially predicting pregnancy problems and its efficacy in pregnancy screening remain subjects of ongoing discussion. The aim of this manuscript is to present current knowledge on CRL discordance.

METHODS

PubMed was searched for related articles with terms "Crown-Rump length", "Prenatal Screening", "Twin pregnancy", "Discordance".

RESULTS

Twenty-two studies were included in our study with six reporting data on monochorionic and 16 assessing the correlation between CRL discordance and adverse pregnancy outcomes. Fetal loss at the 20th and 24th week of the pregnancy, SGA neonates, pre-term delivery (32 weeks), perinatal death (24 weeks) are all reported adverse outcomes associated with CRL discordance. The reported cut-off for increased risk of adverse perinatal outcomes is a discordance of at least 10% or more.

CONCLUSIONS

Increased CRL (>10 %) discordance is linked to a higher risk of sFGR in both monochorionic and dichorionic pregnancies, fetal loss, and preterm delivery.

Survival Outcomes by Fetal Weight Discordance after Laser Surgery for Twin-Twin Transfusion Syndrome Complicated by Donor Fetal Growth Restriction

INTRODUCTION

Management options for treatment of twin-twin transfusion syndrome (TTTS) with severe donor intrauterine growth restriction (IUGR) include fetoscopic laser surgery and umbilical cord occlusion (UCO). We studied perinatal survival outcomes in this select group after laser surgery, stratifying patients by preoperative estimated fetal weight (EFW) discordance.

METHODS

In this retrospective study of monochorionic diamniotic twin gestations with TTTS and selective donor IUGR who underwent laser surgery (2006-2017), preoperative EFW discordance was calculated ([(larger twin - smaller twin)/(larger twin)] × 100) and cases were divided into discordance strata. Severe EFW discordance was defined as >35%. The primary outcome was 30-day donor twin neonatal survival.

RESULTS

The 371 cases were distributed by discordance strata: ≤20% (74 [19.9%]), 21-25% (49 [13.2%]), 26-30% (68 [18.3%]), 31-35% (53 [14.3%]), 36-40% (51 [13.7%]), 41-45% (38 [10.2%]), >45% (38 [10.2%]). Donor 30-day survival declined as the discordance strata increased: 86.5, 85.7, 83.8, 75.5, 64.7, 63.2, and 65.8% (p = 0.0046); 30-day survival was inversely associated with severe discordance (>35%) (64.6 vs. 83.2%, p < 0.0001).

DISCUSSION

In TTTS cases complicated by donor IUGR with severe growth discordance, laser surgery was associated with donor survivorship greater than 60% suggesting that, in this setting, laser surgery remains a reasonable alternative treatment to UCO.

Increased prevalence of fetal thrombi in monochorionic-twin placentas

OBJECTIVE

Fetal vessel thrombosis has been related to pregnancy complications and adverse neonatal outcomes in singleton pregnancies, but the clinical and pathologic characteristics of fetal thrombosis in twin pregnancy are still ill defined.

METHODS

To clarify the characteristics of fetal thrombosis in twins, we reviewed the histology slides and medical records of live-born infants of twin pregnancies involving the live birth of at least 1 fetus (monochorionic: 389 cases; dichorionic: 780 cases) and singleton pregnancies (1162 cases).

RESULTS

The incidence of fetal thrombosis in monochorionic-twin pregnancies was significantly higher than that of dichorionic-twin and singleton pregnancies (5.1% vs 3.0% and 2.8%, respectively). The incidence of velamentous umbilical cord insertion in monochorionic- and dichorionic-twin placentas was also higher than in singleton placentas (12% and 7% vs 2%, respectively). Fetal thrombosis in twin placentas was associated with intrauterine growth restriction. In monochorionic twins, fetal thrombosis was associated with co-twin fetal death, but in dichorionic twins no correlation was identified. Microscopically, fetal vessel thrombosis in twin placentas was associated with vascular cushions (fibrous hyperplasia of fetal vessel), as is the case occasionally in singletons.

CONCLUSIONS

The incidence of fetal vessel thrombosis in monochorionic placentas was higher than that seen in dichorionic-twin placentas and singleton gestations. Fetal vessel thrombosis in twin pregnancies showed a correlation with intrauterine growth restriction, peripheral cord insertions, and major vascular cushions.