BACKGROUND AND PURPOSE:

• Single intrauterine death (sIUD) of one twin is associated with co-twin demise and preterm birth (PTB)
• Previous research suggested the rate of PTB was 68% in monochorionic (MC) twin and 54% in dichorionic (DC) twin pregnancies
  • Limitations include small number of cases | lack of stratification according by GA at sIUD | heterogeneity in perinatal
• D’Antonio et al. (Ultrasound in Obstetrics & Gynecology, 2017) sought to determine whether gestational age at sIUD is associated with PTB

METHODS:

• Retrospective cohort study
• Participants
  • Women with twin pregnancies in 9 hospitals participating in Southwest Thames Obstetric Research Collaborative (STORK), over a 10-year period from 2000
  • Women entered into routine care by 11 weeks
• Exclusions
  • Cases with double fetal loss or sIUD occurring at or after 34 weeks were excluded from analysis
  • Twin-to-twin transfusion syndrome (TTTS), termination of pregnancy and fetal or chromosomal abnormality, pregnancies of unknown chorionicity, MC monoamniotic and high-order multiple gestations were also excluded
• Ultrasound data were matched to hospital delivery records and to a mandatory national register for stillbirth and neonatal loss
• Fetal loss: Defined as spontaneous death occurring after 14 weeks of gestation
• The relative risk (RR) of PTB was assessed
  • At < 34, < 32, and < 28 weeks of gestation in twin pregnancies complicated by sIUD
  • Compared to pregnancies without fetal loss
  • The risk of PTB at < 34 weeks was stratified according to the gestational age at diagnosis of sIUD
  • Chorionicity subgroup analysis also performed
• Risk of PTB at < 34 weeks of gestation after sIUD was explored according to the gestational age at death using 3 time periods
  • 14–19 weeks | 20–25 weeks | 26–32 weeks
• Primary outcome
  • Determine the risk of PTB, stratified according to gestational age at diagnosis of sIUD

RESULTS:

• Following exclusion for miscarriage, TTTS and sIUD >34 weeks, 3013 twin pregnancies were included
  • 2,469 DC and 544 MC
• Incidence of IUD was higher in MC twins (3.9%) compared with DC twin pregnancies (1.9%)
  • Odds ratio (OR) of 2.0 (95% CI, 1.2–3.4; P < 0.006).
• Median gestational age at birth was lower in pregnancies complicated by sIUD (32 weeks) compared with those that were not (36.7 weeks) (P < 0.001)
• The trend persisted when stratifying by chorionicity (P < 0.0001 for both MC and DC pregnancies)
• Compared to twin pregnancies without fetal loss, the risk of PTB was higher in pregnancies with sIUD
  • < 34 weeks: Relative risk (RR) 4.3 (95% CI, 3.5–5.2)
  • < 32 weeks: RR 6.1 (95% CI, 4.6–8.1)
  • < 28 weeks: RR 12.4 (95% CI, 6.9–22.2)
• Increased PTB risk was also observed when stratifying for MC and DC twin gestations
• MC pregnancies affected by sIUD, compared to DC pregnancies 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)
  • This trend remained consistent when stratifying based on chorionicity

CONCLUSION:

• Twin pregnancies complicated by sUID have a significantly higher risk of PTB at <34, <32 and <28 weeks gestation
• This risk is not modified by chorionicity
• The risk of preterm was higher when the sIUD occurred in the second half of pregnancy
• The authors recommend larger multicenter studies to determine the actual risk of spontaneous PTB

Learn More – Primary Sources:

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

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