title: Is gestation in Prader-Willi syndrome affected by the genetic subtype?
abstract: BACKGROUND
  Prader-Willi syndrome (PWS) is a complex genetic disorder with errors in genomic imprinting, generally due to a paternal deletion of chromosome 15q11-q13 region. Maternal disomy 15 (both 15s from the mother) is the second most common form of PWS resulting from a trisomic zygote followed by trisomy rescue in early pregnancy and loss of the paternal chromosome 15. However, trisomy 15 or mosaicism for trisomy 15 may be present in the placenta possibly leading to placental abnormalities affecting gestational age and delivery.
  
  
  METHODS
  We examined growth and gestational data from 167 PWS infants (93 males and 74 females; 105 infants with 15q11-q13 deletion and 62 infants with maternal disomy 15) to determine if there are differences in gestation between the two genetic subtypes.
  
  
  RESULTS
  No significant differences in growth data (birth weight, length, head circumference) or average gestational ages were found between the two genetic subgroups. However, post-term deliveries (> 42 weeks gestation) were more common in the maternal disomy group (i.e., 12 of 62 infants) compared with the deletion group (i.e., 7 of 105 infants) (chi-square test = 6.22; p < 0.02). The distribution of gestational ages in the 15q11-q13 deletion group was more bell-shaped or normal while the distribution in the maternal disomy group suggested a bimodal pattern.
  
  
  CONCLUSIONS
  Maternal disomy 15 in PWS may contribute to disturbances in gestational age and delivery by impacting on placental structure or function secondary to the abnormal chromosomal number in the placental cells or in mechanisms leading to the maternal disomy status in PWS infants.
authors.affiliation: Departments of Psychiatry, Behavioral Sciences and Pediatrics, Kansas University Medical Center, 3901 Rainbow Blvd., MS4015, Kansas City, KS, 66160, USA. mbutler4@kumc.edu
authors.forename: Merlin G
authors.initials: MG
authors.lastname: Butler
authors.forename: Jennifer
authors.initials: J
authors.lastname: Sturich
authors.forename: Susan E
authors.initials: SE
authors.lastname: Myers
authors.forename: June-Anne
authors.initials: JA
authors.lastname: Gold
authors.forename: Virginia
authors.initials: V
authors.lastname: Kimonis
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Driscoll
mesh_terms: D001724:Birth Weight; D001827:Body Height; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D018392:Genomic Imprinting; D005838:Genotype; D005865:Gestational Age; D006801:Humans; D007223:Infant; D008297:Male; D010920:Placenta / Q000473:pathology / Q000503:physiopathology; D011218:Prader-Willi Syndrome / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D011247:Pregnancy; D024182:Uniparental Disomy