The effect of birth interval on perinatal survival and birth weight

Although the effect of a short birth interval on the first child in a pair has received attention in the literature, the effect on the second child has received less. In this article the authors investigate the complex set of relationships between birth interval, maternal age and parity, and their effects on the birth weight and survival of the later-born child.The data consist of 12,995 singleton births to women of parity two or higher during1977 and 1978 in a single hospital. The outcome of the previous pregnancy is controlled by restricting the analysis to women whose previous pregnancy ended in a live infant who is still living at the time of the index birth.The effect of birth interval on birth weight and on survival is examined simultaneously(via logistic regression), with the effects of maternal age and parity. The risks of adverse outcomes as a function of birth interval are estimated by adjusted odds ratios.After adjusting for maternal age and parity, interval was found to be an important precursor of both perinatal mortality and low birth weight. At all levels of maternal age and parity, babies born during a 9- to 12-month birth interval are at greater risk of low birth weight and/or perinatal mortality than babies born after a longer birth interval.