[Establishment method and significance of birthweight curve and reference in single center]

Objective: To establish neonatal birthweight percentile curves based on single-center cohort database using different methods, compare them with the current national birthweight curves and discuss the appropriateness and significance of single-center birthweight standard. Methods: Based on a prospective first-trimester screening cohort at Nanjing Drum Tower Hospital from January 2017 to February 2022, the generalized additive models for location, scale and shape (GAMLSS) and semi-customized method were applied to generate local birthweight percentile curves (hereinafter referred to as the local GAMLSS curves, semi-customized curves) for 3 894 cases who were at low risk of small for gestation age (SGA) and large for gestation age (LGA). Infants were categorized as SGA (birth weight<10th centile) by both semi-customized and local GAMLSS curves, semi-customized curves only, or not SGA (met neither criteria). The incidence of adverse perinatal outcome between different groups was compared. The same method was used to compare the semi-customized curves with the Chinese national birthweight curves (established by GAMLSS method as well, hereinafter referred to as the national GAMLSS curves). Results: (1) Among the 7 044 live births, 404 (5.74%, 404/7 044), 774 (10.99%, 774/7 044) and 868 (12.32%, 868/7 044) cases were diagnosed as SGA according to the national GAMLSS curves, the local GAMLSS curves and the semi-customized curves respectively. The birth weight of the 10th percentile of the semi-customized curves was higher than that of the local GAMLSS curves and the national GAMLSS curves at all gestational age. (2) When comparing semi-customized curves and the local GAMLSS curves, the incidence of admission to neonatal intensive care unit (NICU) for more than 24 hours of infants identified as SGA by semi-customized curves only (94 cases) and both semi-customized and local GAMLSS curves (774 cases) was 10.64% (10/94) and 5.68% (44/774) respectively, both significantly higher than that in non SGA group [6 176 cases, 1.34% (83/6 176); P<0.001]. The incidence of preeclampsia, pregnancy<34 weeks, and pregnancy<37 weeks of infants identified as SGA by the semi-customized curves only and both semi-customized and local GAMLSS curves was 12.77% (12/94) and 9.43% (73/774), 9.57% (9/94) and 2.71% (21/774), 24.47% (23/94) and 7.24% (56/774) respectively, which were significantly higher than those of the non SGA group [4.37% (270/6 176), 0.83% (51/6 176), 4.23% (261/6 176); all P<0.001]. (3) When comparing semi-customized curves and the national GAMLSS curves, the incidence of admission to NICU for more than 24 hours of infants identified as SGA by semi-customized curves only (464 cases) and both semi-customized and national GAMLSS curves (404 cases) was 5.60% (26/464) and 6.93% (28/404) respectively, both significantly higher than that in non SGA group [6 176 cases, 1.34% (83/6 176); all P<0.001]. The incidence of emergency cesarean section or forceps delivery for non-reassuring fetal status (NRFS) in infants identified as SGA by semi-customized curves only and both semi-customized and national GAMLSS curves was 4.96% (23/464) and 12.38% (50/404), both significantly higher than that in the non SGA group [2.57% (159/6 176); all P<0.001]. The incidence of preeclampsia, pregnancy<34 weeks, and pregnancy<37 weeks in the semi-customized curves only group and both semi-customized and national GAMLSS curves group was 8.84% (41/464) and 10.89% (44/404), 4.31% (20/464) and 2.48% (10/404), 10.56% (49/464) and 7.43% (30/404) respectively, all significantly higher than those in the non SGA group [4.37% (270/6 176), 0.83% (51/6 176), 4.23% (261/6 176); all P<0.001]. Conclusion: Compared with the national GAMLSS birthweight curves and the local GAMLSS curves, the birth weight curves established by semi-customized method based on our single center database is in line with our center' SGA screening, which is helpful to identify and strengthen the management of high-risk infants.