Department of Obstetrics and Gynecology Medical School University of Zagreb, Clinical Hospital "Sveti Duh" Zagreb, Croatia; e-mail:
Psychiatr Danub. 2021 May;33(Suppl 3):S280-S291.
Aim is to show that the definition of the infants born at the limits of viability within the countries is dependent on the social and medical conditions in which the infant is born, and even in one country in which neonatal intensive care is available, it depends on the place of birth and organization of perinatal care. With decreasing gestational age mortality, short- and long-term morbidity of preterm infants are increasing while their survival to discharge is decreasing. It is questionable how to define viability and where the limit of viability can be set. The definition of the limits of viability is not quite clear. There are at least two ways of understanding it: the first, defining the gestational age and/or birth weight at which human fetus has the capability of survival outside the uterus; and the second, gestational age and/or birth weight at which more than 50% of infants survive to discharge home from the hospital. While in developing countries infants of less than 28 weeks of gestation without neonatal intensive care have 95% probability of dying, survival of infants between 22 and 25 gestational weeks in developed countries is reaching 90%. Up to now the definition of the limits of viability has not be established, and precise definition of viability scientifically has not been produced yet. Currently, the World Health Organization sets lower limit of viability at 22 weeks of gestation, or 500 g birth weight, or 25 cm of birth length. The universal definition of the limit of viability is probably not possible, because of its variability from one individual to the other, from one setting to the other and from one community to the other.
目的在于表明，各国对极早产儿的定义取决于婴儿出生时的社会和医疗条件，即使在一个提供新生儿重症监护的国家，这也取决于出生地点和围产期护理的组织形式。随着胎龄相关死亡率的降低，早产儿的短期和长期发病率在增加，而他们的存活率却在下降。极早产儿的生存能力如何定义以及其极限在哪里界定，这是值得商榷的。极早产儿极限的定义并不十分明确。至少有两种理解方式：一是定义人类胎儿在子宫外具有生存能力的胎龄和/或出生体重；二是定义有 50%以上的婴儿能够从医院出院回家的胎龄和/或出生体重。在发展中国家，没有新生儿重症监护的 28 周以下的婴儿有 95%的死亡概率，而在发达国家，22 至 25 周胎龄的婴儿的存活率达到 90%。到目前为止，极早产儿极限的定义尚未确立，也尚未从科学上确定极早产儿极限的精确定义。目前，世界卫生组织将极早产儿的下限定义为 22 周妊娠或 500 克出生体重或 25 厘米出生体长。由于极早产儿极限从个体到个体、从环境到环境、从社区到社区都存在差异，因此，极早产儿极限的普遍定义可能是不可能的。
