4.2 Interpretation
In our study, it was demonstrated that the fetal biometric measurements including EFW, AC, FL and HL of SC-DCDA twins were statistically different from those of SC-MCDA twins. To date a few number of studies compared intrauterine growth pattern of DCDA twins to that of MCDA twins6-8, 11-13, 16, and the results were generally consistent and similar to the findings of our study. Among which, a study in Brazil got almost the same result with ours that there were statistically differences in EFW, BPD, AC and FL between monochorionic and dichorionic twin pregnancies11. A multicentric study from Italy also reported that the measurements of EFW, BPD, HC, AC and FL appeared smaller in MCDA group in comparison with DCDA twins, however, the difference didn’t show statistical significance6. When further exploring the week-specific difference for fetal biometric measurements between DCDA and MCDA twins, a study conducted in the US found that DCDA twins had higher sonographic EFW at almost all gestational ages until 34 gestational weeks13, and the data from Italy similarly found that the differences for AC were statistically significant after 33 week of gestation6. The evidence from the two studies provided support for our findings.
Fetal growth velocity has been identified as an important indicator to assess fetal growth and development29. Recently, a national study in the US examined the growth velocity of six parameters including EFW, BPD, HC, AC, HL and FL among singletons and compared the overall differences of these parameters between different racial/ethnic-specific curves30. To our knowledge, no study yet paid attention to the fetal growth velocity among twins. ART has become more common, and an understanding with regard to it’s perinatal outcome is becoming essential17-20. Several studies have, more often than not, focused on the possible impact of ART on birth weight among twin pregnancies, failing to cover intrauterine fetal growth in the concern17-20. As an initial study, we, for the first time, observed the gestational week-specific fetal size and growth velocity among ART-DCDA twins, revealing ART-DCDA twins had the highest growth rate, followed by SC-DCDA, and then SC-MCDA.