Influence of inter-pregnancy interval on preterm delivery

The influence of pregnancy spacing on preterm delivery (<37 weeks gestation) was examined in a group of mothers attending three Maternal and Child Health centres in three different districts in the city of Alexandria, Egypt between October 2001 and July 2002. All pregnant mothers attending the centres were interviewed or had their medical records reviewed. They were followed up until delivery and were questioned about current and past obstetric history and their medical history; their haemoglobin level was measured. The inter-pregnancy interval was calculated as the number of months between the delivery date of the women's last previous live infant and the date of the last menstrual period before the current pregnancy. There were 1202 pregnant women eligible for inclusion. The inter-pregnancy intervals were divided into five categories: <12, 12-36, 37-48, 49-60 and >60 months. We calculated the rates of preterm deliveries for each inter-pregnancy interval. Unadjusted odds ratios were estimated and stepwise logistic regression analysis was then used to adjust for all confounding factors. The rate of preterm delivery was 9.4%, and the lowest risk occurred in women who had an inter-pregnancy interval >60 months; 7.3% of those women gave birth to preterm infants. The rate of preterm delivery increased with increasing inter-pregnancy interval until 49-60 months; however, the association between inter-pregnancy interval and preterm delivery was not statistically significant whether using the crude or adjusted odds ratios.