Relevance. Birth weight is one of the main indicators of intrauterine fetal development. The condition of the placenta reflects the influence of the maternal environment on the fetus. It is important to find out which placental growth parameters significantly affect the mass of dichorionic diamniotic (DHDA) twins.
Objective: to investigate the relationship between indicators of placental growth and birth weight of dichorionic diamniotic twins.
Materials and methods. One hundred thirty-five DCDA twin pairs were studied during 2016-2020: 68 pairs were opposite-sex, 32 – same-sex females and 35 – same-sex males. The gestational age ranged from 29 to 39.5 weeks, averaging 36,4 ± V1,74 weeks. The influence of such parameters as maximum and minimum placental diameters, as well as perimeter, area, circularity (Circ), roundness, thickness, mass (PM), volume (V), displacement of the umbilical cord insertion site from the placental disc centre along its maximum (XCD) and the minimum axis (YCD).
Results. A strong positive correlation was found between PM and birth weight in the whole cohort of DCDA twins (r = 0.7059, p < 0.0001). It was strongest in the same-sex female group (r = 0.7886, p < 0.0001), then in the opposite-sex pairs (r = 0.7093, p < 0.0001), slightly weaker – in the same-sex male couples (r = 0.6065, p < 0.0001). The birth weight and PM correlated with almost all indicators that characterize the placental shape. The strongest correlation was with V (rV_BW = 0.66, p < 0.0001; rV_PM = 0.59, p < 0.0001) and the area*Circ (rS*Circ_BW = 0.64; p < 0.0001; rS*Circ_PM = 0.62; p < 0.0001). The multiple regression analysis of the effect of different morphometric parameters of the placentas on the birth weight has demonstrated the statistical significance of the following parameters: XCD, PM, V, YCD and Circ. The general regression model for the whole DCDA group: birth weight = 2242,3 + 0,8*МП + V – 10,0* XCD (R2 = 0,7002). Similar equations were calculated for different types of DCDA tweens. Thus, morphometric measures account for the 67-85% variances of the birth weight of the DCDA tweens.
Conclusion. In the DCDA pairs, placental mass strongly positively correlated with birth weight. Both indicators are in strong relationship with V and their area*Circ. The closer the placental shape is to the circle, the higher its functional ability. Deterioration of the latter may be due to the far fixation of the umbilical cord from the center of the placental disc. The displacement along the maximum axis has a stronger impact comparing to the displacement relative to the minimum axis. The multiple regression analysis has revealed that statistical significance had XCD and PM or V in the whole types of twins. Proposed models demonstrate that 67-85% of the variability of birth weight may be accounted for by the three or four simple placental measures
Twenty steps towards an adequate inferential interpretation of p-values
