Intrauterine Growth and Gestational Duration Determinants

TLDR

Low birth weight is influenced by many factors, yet it is unclear which have independent causal effects and how large those effects are. The authors reviewed 895 studies from 1970–1984 on 43 potential determinants of intrauterine growth or gestational duration. They applied predefined methodological criteria to select the best studies and evaluate each determinant’s independent causal impact on birth weight, gestational age, prematurity, and intrauterine growth retardation. The review identified determinants with well‑established direct causal impacts, ranked their relative importance for typical developing and developed countries, highlighted modifiable factors with large effects for public health intervention, and flagged determinants of potential quantitative importance but lacking sufficient data as research priorities.

Abstract

Despite the general recognition that low birth weight can be caused by many factors, confusion and controversy remain about which factors have independent causal effects, as well as the quantitative importance of those effects. Previous research findings have often been conflicting because of a failure to distinguish intrauterine growth retardation from prematurity, differences in focus (means v rates), inadequate control for confounding variables, and insufficient statistical power. This review of the English and French language medical literature published between 1970 and 1984 is based on a critical assessment and meta-analysis of 895 studies concerning 43 potential determinants of intrauterine growth or gestational duration. Based on methodologic standards established a priori for each candidate determinant, the best studies were used to assess the existence and magnitude of an independent causal effect on birth weight, gestational age, prematurity, and intrauterine growth retardation. Factors with well-established direct causal impacts are identified, and their relative importance is indicated for "typical" developing and developed country settings. Modifiable factors with large effects are targeted for public health intervention in the two settings. Finally, factors of potential quantitative importance, but for which data are either unavailable or inconclusive, are highlighted as priorities for future research.