Association between rates of premature delivery and intra-uterine growth retardation.
It has been suggested that there is a positive epidemiological correlation between the rates of premature delivery and intra-uterine growth retardation. This was tested across three series of live births, cross-classified according to gravidity and mother's age in two states, North Carolina (caucasians and blacks), and Washington (caucasians only) in the years 1970-74 and 1968-77, respectively. Premature-delivery rate was defined as the percentage of all births of known gestational age born before 37 weeks, and a surrogate measure of the growth-retardation rate as the percentage of all births weighing less than 2500g at term (less than or equal to 40 weeks). The correlations between the two rates for caucasian live births in North Carolina and Washington were found to be +0.74 and +0.73 respectively (p less than 0.0005 in each instance). The correlation coefficient (+0.12 for black live births in North Carolina was not significant. The correlation observed among caucasian births suggest that for growth-retarded fetuses, the risk of subsequent premature delivery is abnormally high.