Intermittent absent and reversed umbilical artery flows in appropriately grown monochorionic diamniotic twins in relation to proximate cord insertion: A harmful combination?

Comparison of pregnancy outcomes and placental characteristics for monochorionic diamniotic twins with and without proximate umbilical cord insertion

INTRODUCTION

This study was developed to evaluate the relative placental characteristics and pregnancy outcomes associated with monochorionic diamniotic (MCDA) twins with and without proximate umbilical cord insertion (PCI).

METHODS

All MCDA twins delivered with complete placentas for whom placental characteristics were assessed via dye injection between April 1, 2013 and April 1, 2021 were included in the present cohort study. Cases were separated into PCI and non-PCI groups, and pregnancy outcomes and placental characteristics were then compared between these groups.

RESULTS

Birthweight discordance rates were significantly lower in the PCI group relative to the non-PCI group (7.3 ± 7.5% vs 29.9 ± 16.8%, P＜0.001), while relative to the non-PCI group, rates of artery-artery (AA), vein-vein (VV), thick AA, and thick VV anastomoses were significantly higher in the PCI group (95.5% vs 67.0%, P = 0.008, 59.1% vs 16.4, P＜0.001,90.5% vs 34.9%, P＜0.001, 54.5% vs 10.5%, P＜0.001). Significantly more anastomoses were observed in the PCI group (7 (3,11) vs 6 (3,15), P = 0.015), and they were significantly larger on average than those in the non-PCI group 12.8 (6.7,21.3) mm vs 11.9 (3.4, 24.6) mm, P = 0.009). Significantly lower placental territory discordance and UCI ratios were evident in the PCI group relative to the non-PCI group (23.5 (15.0,51.0) % vs 60.0 (2.0,80.0) %, P＜0.001, 13.3 ± 5.8% vs 56.1 ± 18.0%, P < 0.001). Marginal cord insertion rates were lower in the PCI group relative to the non-PCI group (13.6% vs 77.5%, P < 0.001).

DISCUSSION

The placental structure of MCDA twins with PCI is distinct from that of twins without PCI, and these results suggest PCI may be indicative of the more even distribution of placental territory between MCDA fetuses.

Intermittent absent and reversed umbilical artery flows in appropriately grown monochorionic diamniotic twins in relation to proximate cord insertion: A harmful combination?

Objective

To compare the prevalence of intermittent absent or reversed end‐diastolic flow (iAREDF) in the umbilical artery in appropriately grown monochorionic diamniotic (MCDA) pregnancies with and without proximate cord insertion (PCI), and to evaluate pregnancy outcome.

Methods

The prevalence of iAREDF in MCDA pregnancies with PCI (n = 11) was compared with a control group without PCI (n = 33). PCI was defined as a distance between the cord insertions below the fifth percentile. Placental sharing, number, and diameter of anastomoses were assessed by placental examination. Pregnancy outcome was evaluated.

Results

iAREDF was present in 7/11 PCI pregnancies, compared with 0/33 in the control group (P ≤ .01). All PCI pregnancies and 94% of controls had arterioarterial (AA)‐anastomoses (P = .56), the diameter was larger in the PCI group, respectively 3.3 vs 2.1 mm (P = .03). Three cases with iAREDF had adverse outcome, two resulted in fetal death of which one with brain damage in the co‐twin, another underwent early premature emergency section for fetal distress.

Conclusion

iAREDF occurs in a large proportion of MCDA pregnancies with PCI and is related to the diameter of the AA anastomosis. We hypothesize that iAREDF in appropriately grown MCDA twin pregnancies reflects an unstable hemodynamic balance with an increased risk for fetal deterioration. Whether outcome in these pregnancies can be improved by altered management requires further investigation.