COMPARATIVE ANALYSIS OF THE NEONATE BIRTH WEIGHT IN DIFFERENT TYPES OF TIN PREGNANCY
Authors: Tepla I. 
Published: April 2021

The relevance of the study lies in the significant increase in multiple pregnancies connected with the higher risk of perinatal complications, the controversy over the effects of chorionicity and sex of the babies on their birth weight, the need for timely diagnosis of fetal growth restriction, and associated morbidity.
The objective of this study was to compare fetal weights at the birth of different variants of twins depending on chorionicity, gestational age, and sex.
Materials and methods. During 2016-2020, 440 pairs of twins were examined: 375 dichorionic diamniotic and 65 monochorionic diamniotic (38 – boys, 27 – girls). Among dichorionic couples there were 186 (49.6%) opposite-sex, 98 (26.1%) same-sex males and 91 (24.3%) same-sex females. Fetal weight was measured at birth, and its relationship to chorionicity, fetal sex, a combination of same-sex or opposite-sex co-twins, and gestational age was assessed.
Results. The average weight of 750 fetuses from dichorionic pairs (2570.0 ± 506.43 g) significantly exceeded the weight of 130 fetuses from monochorionic pairs (2333.4 ± 567.24 g, p < 0.0001). The same-sex male (2603.8 ± 532.29 g) and opposite-sex dichorionic diamniotic (2595.6 ± 490.17 g). twins’ masses significantly surpassed the mass of all other twins (p <0.05). In the group of dichorionic twins, the weight of boys exceeded the weight of girls (2638.1 ± 525.96 g vs. 2499.4 ± 475.84 g, p = 0.0002). This pattern was observed both inside the opposite-sex pairs (2674.2 ± 518.17 g vs. 2517.1 ± 448.24 g, p = 0.0019), and same-sex couples of boys compared to same-sex couples of girls (2603.8 ± 532.29 g and 2481.4 ± 503.08 g, respectively, p = 0.0224). No significant difference in the weight of girls of opposite-sex twins compared to same-sex couples was seen. In monochorionic pairs, the weight of male and female fetuses did not differ significantly. Birth weight discordance was found in all types of twins, the highest percentage of discordance was registered in monochorionic boys – 23.7%, second place in frequency took male dichorionic twins – 20.4%. Among the 30 discordant dichorionic opposite-sex twins in 19 (63.3%) cases, the male fetus was heavier. There was no significant difference in fetal weight when women were fertilized naturally and using assisted reproductive technologies. The average weight of children born by surrogate mothers exceeded the weight of children born by non-surrogate mothers (p = 0.0466). In the first pregnancy, children were born with a lower body weight compared to children born as a result of repeated pregnancies and in women who had a history of childbirth.
Conclusion. The average weight of the fetuses of dichorionic twins was higher than the weight of the neonates f monochorionic pairs. The prevalence of the weight of boys over the weight of girls from dichorionic pairs and the absence of sex difference in fetal weight in monochorionic twins indicates the possibility of different functional activity of the placenta in fetuses of different sexes. Small for gestational age newborns were most often found in the group of female monochorionic twins and opposite-sex dichorionic pairs. Discordance of fetal mass was most common in monochorionic same-sex male twins. In discordant opposite-sex couples, the male fetus more often was heavier. There was no significant difference in newborn weight when women were fertilized naturally and with the use of assisted reproductive technologies. The average weight of surrogate-born children exceeded the weight of children born by non-surrogate mothers. In the first pregnancy, children were born with a lower body weight compared to children of multiparous and multigravida women.