dos Santos Silva Isabel, De Stavola Bianca L, Mann Vera, Kuh Diana, Hardy Rebecca, Wadsworth Michael E J
Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
Int J Epidemiol. 2002 Apr;31(2):405-12. doi: 10.1093/ije/31.2.405.
In recent studies a larger birth size has been shown to delay the timing of menarche. The mechanisms underlying this association are not clear, however, as birthweight is a predictor of body size in childhood, and a large body size is known to be associated with an early onset of menarche.
Data from a representative British cohort of 2547 girls born in 1946 who were followed prospectively throughout childhood were used. Information was available on prenatal characteristics, birthweight, height, weight and social circumstances during childhood, and on age at menarche. Random coefficients models were used to estimate the individual trajectories in height and body mass index (BMI) up to age 7 years. The parameters identified by these models were then included in Weibull survival models for the timing of menarche together with birthweight.
Birthweight was found to positively influence height and BMI values at age 2 years, but not to affect their rates of change from age 2 to 7 years. Initial analyses showed low birthweight to be associated with an early onset of menarche, but after controlling for growth in infancy this effect was reversed, with girls who were heavy at birth reaching menarche earlier than others with similar infant growth. Rapid growth in infancy was also related to early pubertal maturation. The effects of birthweight and infant growth disappeared, however, when further controlled for growth from age 2 to 7 years.
The effects of birthweight and growth in infancy on the timing of menarche seem to be mediated through growth in early childhood. These findings are consistent with the possibility that timing of menarche may be set in utero or early in life, although it may be modified by changes in body size and composition in childhood.
近期研究表明，出生时体型较大与月经初潮时间延迟有关。然而，这种关联背后的机制尚不清楚，因为出生体重是儿童期体型的一个预测指标，而且已知体型较大与月经初潮提前有关。
使用了来自一个具有代表性的英国队列的数据，该队列包含2547名1946年出生的女孩，她们在整个儿童期都接受了前瞻性跟踪。可获得关于产前特征、出生体重、身高、体重以及儿童期社会环境和月经初潮年龄的信息。使用随机系数模型来估计7岁前身高和体重指数（BMI）的个体轨迹。然后将这些模型确定的参数与出生体重一起纳入月经初潮时间的威布尔生存模型中。
发现出生体重对2岁时的身高和BMI值有正向影响，但不影响其从2岁到7岁的变化率。初步分析显示低出生体重与月经初潮提前有关，但在控制婴儿期生长后，这种效应发生了逆转，出生时体重较重的女孩比婴儿期生长情况相似的其他女孩月经初潮更早。婴儿期快速生长也与青春期早熟有关。然而，当进一步控制2岁到7岁的生长情况时，出生体重和婴儿期生长的影响消失了。
出生体重和婴儿期生长对月经初潮时间的影响似乎是通过儿童早期的生长来介导的。这些发现与月经初潮时间可能在子宫内或生命早期就已确定的可能性一致，尽管它可能会受到儿童期体型和身体成分变化的影响。
