Babies born too small are more likely to have low bone mineral density when they grow up, a new study reports today in the Public Library of Science journal, PLoS Medicine.
Researchers in Helsinki, Finland, followed 144 Finns, now aged 18 – 27, who were all born preterm (before 37 weeks of gestation) and with very low birth weight (below 1,500 g – or about 3 lb). These young adults had significantly lower bone mineral density than similar young adults born from a term pregnancy and with normal birth weight. The very small babies also grew up to be much shorter as adults — on average 5.1 cm shorter among men and 4.8 cm shorter among women (a difference of about two inches).
All the study participants were analyzed around what should be the age of peak bone mass. The researchers find it troubling, then, that the low-birth-weight group had such low bone mineral density — a well-known risk factor for osteoporosis. The researchers write that the last trimester of pregnancy is crucial for fetal bone mineralization, with up to 80% of a fetus’s body calcium accruing in the last trimester. They suggest, in the end, that people who were born with very low birth weight might want to be extra-vigilant about maintaining good bone health: getting enough calcium and vitamin D in their diet, and doing weight-bearing exercise.