Background and purpose: Low birth weight (LBW) has adverse influences on lifetime health. This study examined trends in LBW in Taiwan between 1978 and 1997, and assessed the risk of LBW associated with gender, birth order of infant, and parental age at delivery.
Methods: Information on live born singletons for the study period was retrieved from the Taiwan birth registry. We calculated biannual trends for overall LBW rates and for specific demographic factors. Log-linear models with a Poisson assumption were used to assess the linear trend of the LBW rates and the interaction between time and selected demographic factors. Log-linear models were also used to estimate the independent effect of individual demographic factors on the risk of LBW.
Results: The LBW prevalence declined from 6.78% (55,694/820,364) in 1978-79 to 4.95% (30,907/623,971) in 1996-97, representing a 27.10% reduction. The prevalence of LBW showed a noticeable reduction between the late 1970s and mid-1980s, and appeared homogeneous after the mid-1980s. This declining trend was evident for almost all of the selected demographic factors. The only exception was in infants born to teenage fathers, which showed a 10.59% increase in prevalence of LBW during the 20-year study period. Infants born to mothers or fathers aged 35 and above had the greatest reduction (47.58% and 41.44%, respectively) in the rate of LBW, whereas teenage mothers had the lowest reduction (11.75%) in the rate of LBW.
Conclusions: Parental age at an infant birth has a strong association with reduction of LBW risk. Education programs focusing on the problem of teenage pregnancy may accelerate the reduction of LBW.