This cross-sectional study presented neonatal birthweight references of sex-specific twin in different chorionicity between 25 and 40 weeks gestation age, based on population in Guangzhou city, China, during 2015–2019.This study is the first to provide gestational-age-specific weight references based on different dichorionicity for twins in the South of China.
Birth weight is an important indicator of fetal intrauterine development . The use of neonatal birth weight curve to assess infants’ growth is a usual practice. Pediatricians and neonatologists depend one these standards during the decides making if the observed variability of growth curve within the filed of physiological variation or whether it indicates beyond the limits of normal filed . Besides, obstetricians also share the opinion that birthweight percentile charts special for twins deserve emphasis . Percentile charts for fetal weight in given gestational weeks are used as one of the parameters helpful in the evaluation of intrauterine death risk, especially for monochorionic twins.
Thus, some one may argue that the birthweight percentile curve based on different chorionicity in different may not necessary, indeed, the benefit is probably prominent. It was reported that the incidence of stillbirth and neonatal deaths in smaller dichorionic twin small for gestational(SGA) was significantly higher compared with those non-SGA ones. Besides, compared to dichorionic pregnancies, monochorionic pregnancies have a higher risk of adverse outcomes, such as stillbirth, neonatal deaths and morbidities, adverse neurodevelopmental sequelae. Therefore it is indeed need to distinguish the SGA twins and give them intensive care, while give the non-SGA twins routine newborn care. The birthweight percentile curve based on chorionicity and gestational age of twin are helpful as a reference for perinatal health care professionals and researchers to identify the the high risk fetus and neonates who require special care and intensive observation. Thus, using twin growth charts based on chrionicity is likely to prevent the over-diagnosis of SGA in normal growth twins.
Certainly, birth weight for gestational age is an important indicator of the adequacy of fetal growth. While, restricted fetal growth is likely in a causal pathway to all forms of Attention-Deficit/Hyperactivity Disorder (ADHD). In this study, we found that the birthweight of monochorionic twins were lower than dichorionic, and most twins were lighter than singleton neonates in the same gestational age. It was reported that most infants delivered form multiple pregnancies are growth-restricted compared to singleton infants as a result of an adaptive process .Many authors underline the need for a separate estimation for multiples of a reliable range of normal values for fetal and newborn anthropometry [2; 5; 13; 19].
Overall, our study confirmed the basic principle that neonatal birthweight rose up with grater slopes withe the progress of gestational age during the third trimester, which was reported in singleton and twin pregnancies [7; 8; 26]. In addition, we found that the calculated 50th percentile birthweight values of twin boys were higher than those for girls based on the same chorionicity, except monochorionic twins before 31 weeks gestational age. Previous research has extensively documented that boys were born heaver than girls in singleton pregnancies [14; 23] and most twin pregnancies . Besides, the mean birthweight of dichorionic twins were heavier than monochorionic twins within the same sex, which had been reported in other studies based on different races. In contrast, we found that the calculated values of the 50th percentile for monochorionic twin boys were lower than those for girls before 31 weeks gestational age. The reason of this incompatibility need to be research more.
Several limitations of present study deserved to mention. Firstly, this is a single center literature, which may suit for the local region. Secondly, the sample size was relatively small in monochrionic twin infants, due to the chrionicity ratios in twin pregnancies.