Early pregnancy assessment in multiple pregnancies

Counselling in Fetal Medicine: Uncomplicated Twin Pregnancies

Twin pregnancies account for 3% of all pregnancies and they are burdened by higher morbidity and mortality compared to singletons. The role of ultrasound in the screening, diagnosis and management of possible complications of twin pregnancies has been widely investigated in the current literature. However, despite the progress that have been made in the last decades regarding treatment and evidence-based management of complications, twin pregnancies remain at higher risk of adverse outcomes, requiring therefore dedicated surveillance. Thorough counselling regarding the risks and prenatal care should be offered to all future parents of twin pregnancies. This review aims to summarize the current evidence regarding the management of uncomplicated dichorionic and monochorionic pregnancies.

Sonographic evaluation of umbilical cord thickness in monochorionic diamniotic twin pregnancies

OBJECTIVE

To develop a nomogram of the thickness of the umbilical cord (UC) and its components in monochorionic diamniotic (MCDA) twin pregnancies.

METHODS

This prospective longitudinal study involved 47 MCDA twin pregnancies (94 fetuses) between 18 and 33 weeks of gestation. Ultrasound assessments of UC cross-sections and measurements of the umbilical cord area (UCA), the umbilical vein area (UVA), the umbilical artery area (UAA), and the Wharton jelly area (WJA) were made. The UC measurements were correlated with gestational ages. Reference values for the gestational ages of MCDA pregnancies were determined and compared with those of dichorionic twins and singletons. The cases which developed selective intrauterine growth restriction were contrasted with normal cases.

RESULTS

A positive correlation was found between all UC components and gestational age and fetal weight. The UCA of MCDA fetuses was significantly larger than that of DC fetuses (P < 0.001) at the expense of a larger WJA (P < 0.001) and similar to that of singleton pregnancies. The MCDA fetuses with an estimated fetal weight below the 10th percentile had a smaller UCA than fetuses with a normal estimated weight (P < 0.001).

CONCLUSION

The MCDA twins exhibited a thicker UC than that of dichorionic twins. This article is protected by copyright. All rights reserved.

Intertwin discrepancy in middle cerebral artery peak systolic velocity and third-trimester fetal growth restriction in monochorionic-diamniotic twin pregnancy

OBJECTIVES

To assess the role of intertwin discrepancy in middle cerebral artery peak systolic velocity (MCA-PSV) for the prediction of late selective intrauterine growth restriction (sIUGR) at birth and birth weight discrepancy of > 25% (BW-25) in otherwise uncomplicated monochorionic-diamniotic (MCDA) twin pregnancies.

METHODS

This was a cohort study including all MCDA pregnancies followed in a tertiary fetal medicine unit between 2008 and 2013. Exclusion criteria were referral after first trimester, abnormal karyotype, structural anomalies, twin-to-twin transfusion syndrome, twin anemia-polycythemia sequence and sIUGR detected before 28 weeks. MCA-PSV values of both twins measured in the second trimester (18-24 weeks) and early third trimester (26-32 weeks) were converted in multiples of the median (MoM). sIUGR was defined as birth weight < 5(th) centile. The relationship between MCA-PSV discrepancy, sIUGR and BW-25 was assessed by logistic regression analysis. Receiver-operating characteristics (ROC) curves were used to ascertain the predictive value of MCA-PSV discrepancy for such complications.

RESULTS

In total, 136 MCDA twin pregnancies were included in the analysis. Thirty (22.1%) were complicated with sIUGR at birth and 12 (8.8%) were complicated with BW-25. Logistic regression analysis identified MCA-PSV discrepancy as an independent predictor for sIUGR. ROC curves identified third-trimester MCA-PSV discrepancy as the best predictor for both sIUGR (area under ROC curve (AUC), 0.73 (95% CI, 0.62-0.85)) and BW-25 (AUC, 0.79 (95% CI, 0.65-0.93)). The optimal cut-off point for MCA-PSV discrepancy was 0.30 MoM (sensitivity, 70% and specificity, 69% for sIUGR; sensitivity, 83% and specificity, 72% for BW-25).

CONCLUSION

In MCDA twin pregnancies, MCA-PSV discrepancy is associated with both sIUGR at birth and BW discordance. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Cervical length at mid-gestation in screening for preterm birth in twin pregnancy

OBJECTIVE

Short cervical length (CL) in mid-gestation is considered predictive of spontaneous preterm birth (PTB). The medical literature suggests 20 mm as the cut-off for high risk in twin pregnancies. Our objective was to assess the predictive value of CL for spontaneous PTB < 32 weeks' gestation in twin pregnancies and to calculate the cut-off point with the best sensitivity and specificity.

METHODS

This was a single-center retrospective cohort study of women in whom CL had been measured by transvaginal ultrasound at 18-23 weeks' gestation. Pregnancies complicated by twin-to-twin transfusion syndrome, those requiring intrauterine therapy or those with indicated PTB were excluded. The predictive value of CL for PTB < 32 weeks was assessed. The distribution of CL measurements and the optimal cut-off in patients with PTB were calculated and logistic regression analysis was performed to assess the association between pregnancy characteristics and PTB.

RESULTS

A total of 940 twin pregnancies were included. CL showed an area under the receiver-operating characteristics curve of 0.65 (95% CI, 0.58-0.71) for the prediction of PTB < 32 weeks. The optimal cut-off value for predicting PTB was 36 mm (sensitivity, 64.1%; specificity, 62.8%; positive predictive value, 13.5%; negative predictive value, 95.1%; accuracy, 62.9%). The relative risk of PTB with CL ≤ 36 mm was 2.35 (95% CI, 1.53-3.60; P < 0.001). After adjusting for confounders in logistic regression analysis, only CL (adjusted odds ratio (aOR), 0.94 (95% CI, 0.90-0.99); P = 0.03), and not monochorionicity (aOR 4.14 (95% CI, 0.89-19.25); P = 0.07), was independently associated with PTB. More than one-third (36%) of PTB cases delivering < 32 weeks had a normal CL in mid-gestation. This proportion rose to 85% when considering the 20-mm cut-off suggested by the medical literature.

CONCLUSIONS

This study shows that, despite the weak independent association, CL assessed in mid-gestation is a poor predictor of PTB < 32 weeks' gestation in asymptomatic twin pregnancies. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

First-trimester Ultrasound and Aneuploidy Screening in Multifetal Pregnancies

First-trimester ultrasound provides valuable information to help optimize the management of multifetal pregnancies. First trimester ultrasound the use of ultrasound and screening for aneuploidy has been well studied in singleton pregnancies. While evidence supporting the use of ultrasound in multiple gestations is well established, aneuploidy screening continues to evolve and its role in the prenatal setting has been less well studied. We review the importance of early first trimester ultrasound in assessing gestational age and chorionicity and early identification of anomalies, and review the various methods and limitations of aneuploidy screening and invasive diagnostic procedures in multiples.