目的 早产和过期妊娠均可能对新生儿产生不良影响，但关于足月范围内（37⁺⁰~41⁺⁶周）不同孕周分娩新生儿结局差异的研究仍较为有限。因此，本研究旨在通过来自单中心的回顾性妊娠队列，探索足月妊娠不同孕周分娩与不良围产结局之间的潜在关联。方法 回顾性纳入2023年1月至2024年12月在医院分娩的孕产妇及其新生儿，比较不同孕周孕产妇、新生儿特征以及不良结局[大于胎龄儿（LGA）、小于胎龄儿（SGA）、低出生体重儿（LBW）、巨大儿、5分钟Apgar评分≤7、死产]间的差异，并采用限制性立方样条（RCS）模型和多因素logistic回归分析分娩孕周与不良围产结局间的关联。结果 从总共43 502名产妇中，纳入13 123例单胎足月、自然分娩案例，按照分娩孕周分为5组：37⁺⁰~37⁺⁶周组（n=952）、38⁺⁰~38⁺⁶周组（n=2 707）、39⁺⁰~39⁺⁶周组（n=4 920）、40⁺⁰~40⁺⁶周组（n=4 164）、41⁺⁰~41⁺⁶周组（n=380）。高龄产妇（≥35岁）比例随孕周延长而减少，从37⁺⁰~37⁺⁶周组的18.2%下降至41⁺⁰~41⁺⁶周组的10.0%。不同孕周组间孕前BMI分级分布差异有统计学意义（P<0.001），其中37⁺⁰~37⁺⁶周组中超重和肥胖的比例较高，分别为10.7%和1.7%。不同孕周组间孕期体重增长差异有统计学意义（P<0.001），其中41⁺⁰~41⁺⁶周组产妇孕期体重增长较多。妊娠期糖尿病和妊娠期高血压/子痫前期比例在不同孕周组间的差异有统计学意义（P<0.001），均在37⁺⁰~37⁺⁶周组最常见（分别为27.2%和4.3%）。死产15例（0.1%），存活新生儿13 108例，其中LGA 423例（3.2%）、SGA 799例（6.1%）、巨大儿166例（1.3%）、LBW 180例（1.4%）、5分钟低Apgar评分9例（0.1%）。RCS分析初步提示孕39⁺⁰~40⁺⁶周为新生儿不良结局风险较低的窗口期。多因素logistic回归进一步证实，与39⁺⁰~39⁺⁶周相比，37⁺⁰~37⁺⁶、38⁺⁰~38⁺⁶、41⁺⁰~41⁺⁶周分娩的SGA风险明显升高（P<0.01），40⁺⁰~40⁺⁶和41⁺⁰~41⁺⁶周分娩的巨大儿风险显著升高（P<0.001），37⁺⁰~37⁺⁶、38⁺⁰~38⁺⁶周分娩的LBW风险显著升高（P<0.001），41⁺⁰~41⁺⁶周组的5分钟Apgar评分≤7的风险升高（P=0.029），37⁺⁰~37⁺⁶和38⁺⁰~38⁺⁶周分娩的死产风险显著升高（P<0.01）。结论 足月妊娠不同分娩时机可能影响新生儿结局，孕39⁺⁰~40⁺⁶周是各项不良结局风险均处于较低水平的窗口期。本研究对临床进一步优化妊娠监测和围产期管理可能具有潜在的价值。

Objective Both preterm and postterm pregnancies can adversely affect neonatal outcomes; however, research on the differences in neonatal outcomes across various gestational ages within the full-term range (37⁺⁰ to 41⁺⁶ weeks) remains limited. Therefore, this study aims to explore the potential association between the gestational week of delivery within full-term pregnancy and adverse perinatal outcomes using a retrospective pregnancy cohort from a single center. Methods A retrospective cohort of pregnant women who delivered at hospital between January 2023 and December 2024, and their neonates, was included. Maternal and neonatal characteristics, as well as adverse outcomes [including large for gestational age (LGA), small for gestational age (SGA), low birth weight (LBW), macrosomia, 5-minute Apgar score≤7, and stillbirth], were compared across different gestational weeks. Restricted cubic spline (RCS) models and multivariable logistic regression were employed to analyze the association between gestational week at delivery and adverse perinatal outcomes. Results A total of 13,123 singleton full-term natural delivery cases were included from 43,502 parturients. They were included and categorized into five groups according to gestational week at delivery: the 37⁺⁰-37⁺⁶ weeks group (n=952), the 38⁺⁰-38⁺⁶ weeks group (n=2,707), the 39⁺⁰-39⁺⁶ weeks group (n=4,920), the 40⁺⁰-40⁺⁶ weeks group (n=4,164), and the 41⁺⁰-41⁺⁶ weeks group (n=380). The proportion of advanced maternal age (≥35 years) decreased with increasing gestational age, declining from 18.2% in the 37⁺⁰-37⁺⁶ weeks group to 10.0% in the 41⁺⁰-41⁺⁶ weeks group. The distribution of pre-pregnancy BMI categories differed significantly among the gestational age groups (P<0.001), with the 37⁺⁰-37⁺⁶ weeks group having higher proportions of overweight and obesity (10.7% and 1.7%, respectively). Gestational weight gain also varied significantly across groups (P<0.001), with the 41⁺⁰-41⁺⁶ weeks group exhibiting greater weight gain during pregnancy. The incidence of gestational diabetes mellitus (GDM) and hypertensive disorders of pregnancy/preeclampsia differed significantly among gestational age groups (P<0.001), both being most prevalent in the 37⁺⁰-37⁺⁶ weeks group (27.2% and 4.3%, respectively). There were 15 stillbirths (0.1%), 13,108 surviving newborns, among whom 423 newborns (3.2%) were LGA, 799 (6.1%) were SGA, 166 (1.3%) were macrosomia, 180 (1.4%) were LBW, and 9 (0.1%) had a low Apgar score at 5 minutes. Restricted cubic spline analysis initially suggested that 39⁺⁰-40⁺⁶ weeks of gestation might represent a window of lower risk for adverse neonatal outcomes. Multivariate logistic regression further confirmed that, compared with delivery at 39⁺⁰-39⁺⁶ weeks, delivery at 37⁺⁰-37⁺⁶ weeks and 38⁺⁰-38⁺⁶ weeks was associated with a significantly increased risk of SGA (P<0.01); delivery at 40⁺⁰-40⁺⁶ weeks and 41⁺⁰-41⁺⁶ weeks was associated with a significantly increased risk of macrosomia (P<0.001); delivery at 37⁺⁰-37⁺⁶ weeks and 38⁺⁰-38⁺⁶ weeks was associated with a significantly increased risk of LBW (P<0.001); the 41⁺⁰-41⁺⁶ weeks group had an increased risk of a 5-minute Apgar score≤7 (P=0.029); and delivery at 37⁺⁰-37⁺⁶ weeks and 38⁺⁰-38⁺⁶ weeks was associated with a significantly increased risk of stillbirth (P<0.01). Conclusions The timing of delivery in full-term pregnancies may affect neonatal outcomes. The period from 39⁺⁰ to 40⁺⁶ weeks of gestation is a window during which the risks of various adverse outcomes are at relatively low levels. This study may have potential value for further optimizing clinical pregnancy monitoring and perinatal management.