Size at birth and its relation to muscle strength in young adult women.

OBJECTIVE: To assess the relationship between development in utero, assessed by birth weight, and muscle strength in young adult women as assessed by grip strength. METHODS: A total of 1563 participants aged 20-40 years in the Southampton Women's Survey had their grip strength measured during pregnancy. At recruitment to the survey the women had been asked to recall their birth weight or obtain it from their parents. For 536 women born in Southampton, birth weight was obtained from hospital records. Grip strength was related to birth weight using multiple linear regression analysis, adjusting for age, height, weight and reported physical activity. RESULTS: Grip strength increased with age, height, weight, physical activity and birth weight. In the mutually-adjusted model, grip strength increased by 1.10 kg per kilogram of birth weight (95% CI: 0.58-1.61 kg). In women with hospital birth weight data the relationship strengthened to 1.44 kg per kilogram of birth weight (95% CI: 0.50-2.38 kg). CONCLUSIONS: Grip strength in women in their twenties and thirties is at or approaching its peak. The association between grip strength and birth weight was remarkably similar to findings from other studies of women at younger and older ages. This indicates that in utero development has consequences for muscle strength throughout the life course, even allowing for the increase to peak muscle strength and then its decline as a woman ages.