Comparative Development of Surviving Co-Twins of Vanishing Twin Conceptions, Twins and Singletons

Influence of chorionicity and gestational age at single fetal loss on risk of preterm birth in twin pregnancy: analysis of STORK multiple pregnancy cohort

OBJECTIVE

Single intrauterine death (sIUD) in twin pregnancy is associated with a significant risk of cotwin demise and preterm birth (PTB), especially in monochorionic (MC) twins. However, it is yet to be established whether the gestational age at loss may influence the pregnancy outcome. The aim of this study was to explore the risk of PTB according to the gestational age at diagnosis of sIUD.

METHODS

This was a cohort study of all twin pregnancies booked for antenatal care in a large regional network of nine hospitals over a 10-year period. Ultrasound data were matched to hospital delivery records and to a mandatory national register for stillbirth and neonatal loss provided by the Centre for Maternal and Child Enquires. Cases with double fetal loss at the time of the scan and cases of sIUD occurring at or after 34 weeks of gestation were not included in the analysis. The relative risk (RR) of PTB at < 34, < 32 and < 28 weeks of gestation in twin pregnancies complicated by sIUD was assessed and compared with that in twin pregnancies without fetal loss. The risk of PTB at < 34 weeks was stratified according to the gestational age at diagnosis of sIUD. The risk of PTB in twin pregnancy after sIUD according to the gestational age at death was also explored.

RESULTS

The analysis included 3013 twin gestations (2469 dichorionic (DC) and 544 MC). Median gestational age at birth was lower in the pregnancies complicated by sIUD compared with those that were not (32.0 weeks: interquartile range (IQR), 29.0-34.3 weeks vs 36.7 weeks: IQR, 35.0-37.6; P < 0.001) and this difference persisted when stratifying the data according to chorionicity (P < 0.0001 for both MC and DC pregnancies). The risk of PTB at < 34 weeks (RR, 4.3 (95% CI, 3.5-5.2)), < 32 weeks (RR, 6.1 (95% CI, 4.6-8.1)) and < 28 weeks (RR, 12.4 (95% CI, 6.9-22.2)) of gestation was higher in pregnancies complicated by sIUD compared with those which did not experience fetal loss. This association was observed both in MC and DC twin gestations. When compared with DC pregnancies, MC twins affected by sIUD were not at significantly increased risk of PTB before either 34, 32 or 28 weeks of gestation. The risk of PTB at < 34 weeks of gestation was higher when the sIUD occurred at a later gestational age (chi-square test for trend, P < 0.001).

CONCLUSIONS

Twin pregnancies complicated by sIUD, regardless of the chorionicity, have a significantly higher risk of PTB at < 34, < 32 and < 28 weeks of gestation. The risk of PTB at < 34 weeks of gestation was higher when the sIUD occurred in the second half of the pregnancy. Large prospective multicenter studies with shared protocols for prenatal management are needed to ascertain the actual risk of spontaneous PTB in twin pregnancies affected by sIUD. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Monozygotic Twinning

This article discusses pathologies found in monozygotic twinning. Detailed information is provided regarding the development during monozygotic twin formation: embryo development, twin-to-twin transfusion syndrome, acardiac twinning, vanishing twins, conjoined twins, and Beckwith-Weidmann syndrome twins. An algorithm describing the approach for identifying pathology in a placenta with multiple pregnancies is presented.

Gonadotrophin ovulation induction and enhancement outcomes: analysis of more than 1400 cycles

Ovulation induction (OI) or ovulation enhancement (OE) with gonadotrophins can be a reasonable treatment option for patients with a variety of infertility diagnoses. It must be used with extensive monitoring and management given the risk of multiple pregnancy,especially high-order multiples. This retrospective study evaluated per cycle outcomes of a large cohort of 1452 gonadotrophin OI/OE cycles at an academic infertility centre, and the efficacy of specific guidelines in limiting multiple pregnancy. The lowest possible gonadotrophin doses were used and cycle cancellation was recommended if more than three dominant follicles were present, and/or ifserum oestradiol was above 1500 pg/ml. Overall, pregnancy rate (PR) was 12% and live birth rate was 7.7%, with an increasing trend in younger patients (P = 0.0002 and <0.0001, respectively). Multiple clinical PR was 2.6% with 1.9% twins and 0.7% triplets and above.The birthweight of a singleton from a vanishing twin pregnancy (n = 8)was significantly lower than other singletons (2882 g versus 3250 g,P = 0.013). Reducing multiple pregnancies from OI/OE cycles remains an important and challenging goal. In this large cohort, high-order multiple clinical PR was limited to 0.7% per cycle by using specific management strategies while maintaining a reasonable PR.

Single twin demise: consequence for survivors

Multiple pregnancies, the majority of which are twins, are at substantially higher risk of fetal morbidity and mortality when compared with singleton pregnancies. Single fetal demise occurs in up to 6.2% of all twin pregnancies. It may cause considerable risk for the co-twin including increased risk of fetal loss, premature delivery, neurovascular injury and end-organ damage. In this review we seek to summarise the most contemporary literature on the aetiology of single twin demise, the pathophysiology of injury to the surviving twin and the evidence for current management strategies.