Advertisement

Discordance in umbilical artery resistance in twin pregnancies

  • Jackie Chyu
    Affiliations
    1University of Colorado Health Sciences Center, Obstetrics and Gynecology, Denver, CO 2University of Colorado Health Sciences Center, Pediatrics, Denver, CO USA
    Search for articles by this author
  • John Hobbins
    Affiliations
    1University of Colorado Health Sciences Center, Obstetrics and Gynecology, Denver, CO 2University of Colorado Health Sciences Center, Pediatrics, Denver, CO USA
    Search for articles by this author
  • Henry Galan
    Affiliations
    1University of Colorado Health Sciences Center, Obstetrics and Gynecology, Denver, CO 2University of Colorado Health Sciences Center, Pediatrics, Denver, CO USA
    Search for articles by this author

      Objective

      To compare umbilical artery (UA) discordance in growth-restricted fetuses of twin pregnancies with and without twin-twin transfusion syndrome (TTTS).

      Study Design

      In this longitudinal study, 16 donor twins in TTTS, 13 fetal growth–restricted (FGR) twins in dichorionic diamniotic pregnancies, and 54 normal twin controls underwent 77, 41, and 109 Doppler studies of each UA, respectively. UA flow velocity waveforms were obtained from the midsection of the cord during fetal apnea using duplex real-time color and Doppler ultrasound. In order to ensure sampling of each UA, both UAs were visualized in parallel fashion at the time of sampling. The systolic to diastolic ratio (S/D) was calculated when at least 3 consecutive uniform waveforms were obtained. Normality test and ANOVA were used to compare the mean differences in S/D ratios (Delta S/D) of each group. Fetal growth restriction was confirmed by birthweight less than the 10th percentile using Denver neonatal growth curves, and chorionicity was confirmed by pathology in all cases.

      Results

      There was no difference in mean Delta S/D between the control and TTTS groups (0.40±0.03 vs 0.58±0.07; P = 0.12). However, the mean Delta S/D in the FGR group was significantly greater than that of the control group (0.58±0.08 vs 0.40±0.03; P<0.029). Viewed alternatively, there was, on average, a 13% discrepancy between the umbilical arteries for the S/D ratio in the FGR group.

      Conclusion

      Elevated UA resistance is a known indicator of placental abnormality downstream to flow, such as villous maldevelopment or infarction. The finding of discordance in UA resistances in dizygotic growth-restricted fetuses but not in fetuses small due to TTTS is consistent with the concept that the UA discordance is due to the umbilical arteries feeding areas of placenta with pathology different from the placental pathology of donor twins in TTTS.