Size at Birth Predicts Age at Menarche
Authors: Adair Linda S. 
Published: August 2004

Objective.
This study examines the relationship of intrauterine growth, measured by size and maturity at birth, to age at menarche, while also considering a wide range of other factors that may affect maturation. The research is motivated by the current debate about the importance of the prenatal environment as a determinant of later disease risk.

Methods.
Data were collected during the Cebu Longitudinal Health and Nutrition Survey. This community-based study has followed a cohort of several thousand Filipino infants since their birth in 1983 to 1984. Participants live in urban and rural communities of Metro Cebu, the second largest metropolitan area of the Philippines. The analysis sample includes 997 girls 14 to 15 years of age. The main outcome measure is age at menarche, determined from girls' self-report of the month and year of first menses. Factors that influenced age at menarche were identified using Weibull parametric survival time models. The main exposure variables of interest included weight and length (measured by trained field staff) and gestational age (assessed from mother's reported date of last menstrual period, augmented by clinical assessments at birth). The analysis also takes into account a wide range of other factors that are likely to affect age at menarche. These include the girls' early postnatal growth rates, premenarcheal body composition (body mass index and skinfold thicknesses measured at 8 years), current diet (measured by two 24-hour dietary recalls), and socioeconomic conditions of the household in which they live. We also assessed the contribution of maternal characteristics, including age at menarche, height, and nutritional status while pregnant with the study child.

Results.
The median age at menarche calculated from the hazard model is 13.1 years, with 50% of girls attaining menarche between 12.4 and 13.9 years. Earlier menarche is characteristic of girls who live in urban, higher socioeconomic status households, as indicated by higher maternal education, better housing quality, and possession of assets, such as a TV or refrigerator. Age at menarche is significantly associated with birth characteristics. Although birth weight alone was not significantly related to age at menarche, girls who were relatively long and thin at birth (&gt;49 cm, &lt;3 kg) attained menarche ∼6 months earlier than did girls who were short and light (&lt;49 cm, &lt;3 kg). This effect of thinness at birth is most pronounced among girls with greater than average growth increments in 6 months of life. The effects of birth size are not modified when body mass index and skinfold thicknesses at 8 years are taken into account. Effects of birth size on age at menarche also remain significant when maternal nutritional status during pregnancy and the girl's current diet and socioeconomic indicators are taken into account.

Conclusions.
The study provides additional evidence of fetal programming of later health outcomes by showing that future growth and maturation trajectories are established in utero. Furthermore, rapid postnatal growth potentiates the effects of size at birth and is related independently to earlier pubertal maturation.