Kanazawa Satoshi, Awata Yoko
Department of Management, London School of Economics and Political Science, Houghton Street, London, WC2A 2AE, UK.
Reprod Sci. 2025 Feb;32(2):526-534. doi: 10.1007/s43032-024-01767-6. Epub 2025 Jan 8.
In an attempt to stimulate further theory and research on only children, we introduce two conceptual distinctions: Only children as independent variables vs. only children as dependent variables; and only children by choice vs. only children by circumstances. What little scientific research exists on only children to date focuses almost exclusively on only children as independent variables and fails to make a distinction between only children by choice and only children by circumstances. A focus on only children by choice as dependent variables explores the question of why some women choose to have only one child. As an empirical illustration, analyses of prospectively longitudinal data with a nationally representative sample in the United Kingdom (National Child Development Study) show that women who experience pregnancy complications are significantly less likely to have another child and significantly more likely to have only one child. Our results suggest that increased chances of pregnancy complications that American women now experience alone can explain about 10% of the increase in the number of only children in the United States in the last half century. If certain genes incline women to have pregnancy complications, it is possible that only children by circumstances are genetically more similar to children with siblings than to only children by choice.
为了推动关于独生子女的进一步理论和研究，我们引入两个概念区分：作为自变量的独生子女与作为因变量的独生子女；以及出于选择的独生子女与出于环境因素的独生子女。迄今为止，关于独生子女的少量科学研究几乎完全集中在作为自变量的独生子女上，并且没有区分出于选择的独生子女和出于环境因素的独生子女。将出于选择的独生子女作为因变量进行研究，探讨的是为什么有些女性选择只生育一个孩子的问题。作为一个实证例证，对英国具有全国代表性样本的前瞻性纵向数据（全国儿童发展研究）进行分析表明，经历过妊娠并发症的女性生育第二个孩子的可能性显著降低，而只生育一个孩子的可能性显著增加。我们的研究结果表明，美国女性现在独自面临的妊娠并发症几率增加，可以解释美国过去半个世纪独生子女数量增长的约10%。如果某些基因使女性易出现妊娠并发症，则有可能出于环境因素成为独生子女的人与有兄弟姐妹的孩子在基因上比与出于选择成为独生子女的人更相似。
