Effect of chorionicity on perinatal outcomes in triplet pregnancies beyond the first trimester

Monochorionic placentation in triplet pregnancy has been a pertinent factor in clinical outcomes. However, uncertainty remains because of limited recent data and the heterogeneous strategies. A single tertiary centre study can provide informative in-hospital data on the contemporary status of obstetric practice. This study aimed to evaluate the obstetric and perinatal outcomes of triplet pregnancies according to chorionicity. This study included a cohort of consecutive pregnant women with triplets confirmed on ultrasound scans at 7–14 weeks of gestation from 2007-2022. Beyond the first trimester, 384 trichorionic-triamniotic (TCTA), 157 dichorionic-triamniotic (DCTA), and 18 monochorionic-triamniotic (MCTA) triplet pregnancies were observed. Twenty-six cases were lost to follow-up. Obstetric and perinatal outcomes (from ≥24 weeks of gestation to the first 28 days of life) were compared by chorionicity, with pertinent observations to monochorionic pairs of DCTA triplets. Generalised estimating equations were adopted to determine the significant difference of the outcomes by chorionicity. Of 537 sets of triplets, monochorionic placentation (n = 163) was significantly associated with an increased risk of overall mortality (OR, 1.94; 95% CI, 1.11–3.37, P=.019, ρ=.615). The effect of monochorionicity in the triplet pregnancies was associated mainly with miscarriage (OR, 2.38; 95% CI, 1.14–4.96, P=.021, ρ=.811). However, there were no significant differences in perinatal mortality rates (DCTA triplets 10/354[2.8%] vs. TCAT triplets 16/1026[1.5%], P=.13, ρ=.431) and neonatal morbidity rates of liveborn triplets (DCTA triplets 47/351 [13.4%] vs. TCTA triplets 102/1018 [10.0%], P=.29, ρ=.548). In triplet pregnancies, monochorionicity was associated with an increased risk of miscarriage, but not of the adverse neonatal outcome. Additional prospective studies may further refine clinical risk stratification of expectant management.