Joffe M
Department of Community Medicine, St Mary's Hospital Medical School, London, England.
Soc Sci Med. 1989;28(6):613-9. doi: 10.1016/0277-9536(89)90256-6.
The risk of giving birth to a low birth weight baby is known to be associated with poor material circumstances during the mother's own childhood. In addition to this long-term effect, an association is also apparent of low birth weight with the mother's current social class, measured in terms of her husband's occupation. At least two interpretations of this are possible: a true short-term effect, and/or selective social mobility (upward or downward). According to the latter hypothesis, social class at marriage reflects the operation of selective social processes such that taller and better educated women tend to marry men of higher social class: because both attributes are negatively associated with the risk of low birth weight, a short-term effect is mimicked. This paper investigates the strength of this effect, using data from a longitudinal study, the National Child Development Study. The possibility is also explored that the social class gradients at different ages are not independent: for example that a beneficial socio-economic environment in early life can compensate for hardship later on, in terms of the risk of low birth weight, and vice versa. A social class gradient was observed in the proportion of low birth weight deliveries, both at the time of the respondent's own birth and at the time of her marriage. Depending on the assumption made concerning the relationship of height with low birth weight, selective mobility for height explained 10.7% or 16.3% of the apparent short-term gradient in low birth weight. Selective mobility for educational level did not have any effect. Further analyses suggested that having belonged to a higher social class either in early childhood or at marriage had a beneficial effect, notwithstanding the direction of any mobility experienced. The social class of the woman's father when she was 16 was not associated with the low birth weight rate, and upward mobility during the respondent's childhood appeared to carry an increased risk.
众所周知，出生时体重过轻的风险与母亲童年时期贫困的物质环境有关。除了这种长期影响外，出生时体重过轻还与母亲目前的社会阶层明显相关，这是根据其丈夫的职业来衡量的。对此至少有两种解释：一种是真正的短期影响，和/或选择性社会流动（向上或向下）。根据后一种假设，结婚时的社会阶层反映了选择性社会过程的作用，即身材较高且受教育程度较高的女性往往嫁给社会阶层较高的男性：由于这两个特征都与出生时体重过轻的风险呈负相关，所以会出现一种短期影响。本文利用一项纵向研究——全国儿童发展研究的数据，调查了这种影响的强度。同时还探讨了不同年龄的社会阶层梯度并非相互独立的可能性：例如，早年有利的社会经济环境可以在出生时体重过轻的风险方面弥补后期的艰难处境，反之亦然。在被调查者出生时以及结婚时，出生时体重过轻的分娩比例中都观察到了社会阶层梯度。根据关于身高与出生时体重过轻关系的假设，身高的选择性流动解释了出生时体重过轻明显短期梯度的10.7%或16.3%。教育水平的选择性流动没有任何影响。进一步的分析表明，无论经历何种流动方向，童年早期或结婚时属于较高社会阶层都有有益影响。被调查者16岁时其父亲的社会阶层与出生时体重过轻的比率无关，而且被调查者童年时期向上流动似乎会带来更高的风险。
