title: De novo chromosomal abnormalities and month of conception.
abstract: OBJECTIVE
  We set out to study the possible relationship between the occurrence of chromosomal abnormalities and the month of conception using data from 7 years of prenatal diagnosis.
  
  
  METHODS
  The sample included 7439 cytogenetic analyses from amniocentesis performed for conceptions between 1997 and 2003. The monthly prevalence of all de novo chromosomal abnormalities, trisomies, including trisomy 21, and Robertsonian translocations was investigated.
  
  
  RESULTS
  Two hundred and four de novo numerical and structural chromosomal abnormalities (2.7%) were detected. A significant decrease in the frequencies of all de novo chromosomal abnormalities for June conceptions, as well as lower summer occurrences of trisomy 21, were found. In addition, de novo Robertsonian translocations were unexpectedly detected only among December conceptions.
  
  
  CONCLUSIONS
  The relationship between chromosomal abnormalities and the month of conception could turn out to be useful in estimating the actual risk in pregnancy, if confirmed by other studies. The observed June lowest rate might indicate an association between chromosomal abnormalities and the maximum number of daylight hours throughout the year (summer solstice). We cannot explain the unusual findings concerning Robertsonian translocations that were only found for conceptions in December. This may be related to the annual minimum daylight hours (winter solstice) as opposed to the summer solstice.
authors.affiliation: Division of Biology and Genetics, Department of Biomedical Sciences and Biotechnology, University of Brescia, Italy.
authors.forename: Mariella
authors.initials: M
authors.lastname: Tonelli
authors.forename: Claudia
authors.initials: C
authors.lastname: Specchia
authors.forename: Adriano
authors.initials: A
authors.lastname: Decarli
authors.forename: Sergio
authors.initials: S
authors.lastname: Barlati
mesh_terms: D000649:Amniocentesis; D016010:Binomial Distribution; D002869:Chromosome Aberrations / Q000706:statistics & numerical data*; D004314:Down Syndrome; D005260:Female; D005306:Fertilization; D005865:Gestational Age; D006801:Humans; D007621:Karyotyping; D016014:Linear Models; D011247:Pregnancy; D011296:Prenatal Diagnosis; D015995:Prevalence; D012621:Seasons