Department of Obstetrics and Gynecology, University of Western Ontario, London, Canada; Department of Physiology and Pharmacology, University of Western Ontario, London, Canada; Department of Pediatrics, University of Western Ontario, London, Canada; Lawson Health Research Institute, University of Western Ontario, London, Canada.
Department of Obstetrics and Gynecology, University of Western Ontario, London, Canada; Lawson Health Research Institute, University of Western Ontario, London, Canada.
Early Hum Dev. 2022 Jan;164:105511. doi: 10.1016/j.earlhumdev.2021.105511. Epub 2021 Nov 20.
We determined the impact of gestational age (GA) from near term to term to post-term on birth/placental weight ratio and cord oxygen values with implications for placental transport efficiency for oxygen, fetal O consumption relative to delivery or fractional O extraction, and oxygen margin of safety.
A hospital database was used to obtain birth/placental weight ratios, cord PO and other information on patients delivering between Jan 1, 1990 and Jun 15, 2011 with GA > 34 completed weeks (N = 69,852). Oxygen saturation was calculated from the cord PO and pH data, while fractional O extraction was calculated from the oxygen saturation data. The effect of GA grouping on birth/placental weight ratio, cord PO, O saturation, and fractional O extraction values, was examined in all patients adjusting for pregnancy and labor/delivery covariates, and in a subset of low-risk patients.
Birth/placental weight ratio and umbilical venous O values increased with advancing GA, supporting the conjecture of increasing placental transport efficiency for oxygen. However, umbilical arterial O values decreased while fractional O extraction increased with successive GA groupings, indicating that fetal O consumption must be increasing relative to delivery.
Fetal O consumption can be seen as ever 'outgrowing' O delivery over the last weeks of pregnancy and leading to a continued lowering in systemic oxygen levels. While this lowering in oxygen may trigger feedback mechanisms with survival benefit, the 'oxygen margin of safety' will also be lowered increasing perinatal morbidity and mortality which appear to be hypoxia related.
我们确定了从近足月到足月到过期妊娠的胎龄（GA）对出生/胎盘重量比和脐带氧值的影响，这对胎盘的氧气转运效率、胎儿相对于分娩的 O 消耗或分数 O 提取以及氧气安全边际有影响。
使用医院数据库获取 1990 年 1 月 1 日至 2011 年 6 月 15 日期间 GA>34 周分娩的患者的出生/胎盘重量比、脐带 PO 和其他信息（N=69852）。根据脐带 PO 和 pH 值数据计算氧饱和度，根据氧饱和度数据计算分数 O 提取。在所有患者中，调整妊娠和分娩/分娩相关协变量后，以及在低危患者亚组中，检查 GA 分组对出生/胎盘重量比、脐带 PO、O 饱和度和分数 O 提取值的影响。
出生/胎盘重量比和脐静脉 O 值随着 GA 的增加而增加，支持了氧气转运效率增加的假说。然而，随着连续的 GA 分组，脐动脉 O 值降低而分数 O 提取增加，表明胎儿相对于分娩的 O 消耗必须增加。
可以认为胎儿 O 消耗在妊娠的最后几周内“超过”O 输送，导致全身氧水平持续降低。虽然这种氧的降低可能会引发具有生存益处的反馈机制，但“氧气安全边际”也会降低，增加围产期发病率和死亡率，这似乎与缺氧有关。
