title: Short interpregnancy interval and low birth weight: A role of parity.
abstract: OBJECTIVE
  Short interpregnancy intervals (IPI) and high parity may be synergistically associated with the risk of unfavorable pregnancy outcomes. This study tests if the effect of short IPI on the odds ratio for low birth weight (LBW, <2,500 g) differs across parity status.
  
  
  METHODS
  The study was carried out on the birth registry sample of almost 40,000 singleton, live-born infants who were delivered between the years 1995 and 2009 to multiparous mothers whose residence at the time of infant's birth was the city of Krakow. Multiple logistic regression analyses were used for testing the effect of IPI on the odds ratio (OR) for LBW, after controlling for employment, educational and marital status, parity, sex of the child, maternal and gestational age. Stratified analyses (according to parity) and tests for interaction were performed.
  
  
  RESULTS
  Very short IPI (0-5 months) was associated with an increased OR for LBW, but only among high parity mothers with three or more births (OR = 2.64; 95% CI 1.45-4.80). The test for interaction between very short IPI and parity on the OR for LBW was statistically significant after adjustment for multiple comparisons (P = 0.04). Among low parity mothers (two births) no statistically significant associations were found between IPI and LBW after standardization.
  
  
  CONCLUSIONS
  Parity may modify the association between short birth spacing and LBW. Women with very short IPI and high parity may have a higher risk of having LBW infants than those with very short IPI but low parity.
authors.affiliation: Department of Health and Medical Sciences, Andrzej Frycz Modrzewski Krakow University, ul. Gustawa Herlinga-Grudzińskiego 1, 30-705, Krakow, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Merklinger-Gruchala
authors.affiliation: Department of Environmental Health, Faculty of Health Sciences, Jagiellonian University Medical College, ul. Grzegorzecka 20, 31-531, Krakow, Poland.
authors.forename: Grazyna
authors.initials: G
authors.lastname: Jasienska
authors.affiliation: Department of Health and Medical Sciences, Andrzej Frycz Modrzewski Krakow University, ul. Gustawa Herlinga-Grudzińskiego 1, 30-705, Krakow, Poland.
authors.forename: Maria
authors.initials: M
authors.lastname: Kapiszewska
mesh_terms: D001721:Birth Intervals; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D016017:Odds Ratio; D010298:Parity; D011044:Poland / Q000453:epidemiology; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology* / Q000209:etiology; D012307:Risk Factors