title: Effect of religious rules on time of conception in Romania from 1905 to 2001.
abstract: OBJECTIVE
  Does the interdiction of sexual intercourse during Nativity and Lent fasting periods have any effect on when babies are conceived in Romania, in the 20th century?
  
  
  CONCLUSIONS
  Based on date of birth records from the 20th century, Lent had a greater effect than the Nativity fast on conception within the Eastern Orthodox (ORTHD) population.
  
  
  BACKGROUND
  Seasonality of births (and therefore of conception) is affected by geographical factors (latitude, weather, day-length). Other demographic, economic and socio-cultural characteristics (education, ethnicity, religion) have been proved to have an influence on conception.
  
  
  METHODS
  The analyzed data consists of registered daily birth records for a long time series (35 429 points = 365 (days/year) × 97 years + 24 leap years), with 24 947 061 births in Romania over the period 1905-2001. The data were obtained from the 1992 and 2002 censuses.
  
  
  METHODS
  Based on the reported birth date of each person, the estimated date of conception is computed using a standard gestation period of 280 days. The population was grouped into two categories (ORTHD and Non-Orthodox (NORTHD)) based on religious affiliation. Data analysis is performed in the same manner for both groups. Preliminary data analyses regarding seasonal variations in conception are considered first. Econometric models are applied and tested. The dependent variable in these models is the calculated date of conception, while the independent variables are: (i) religious affiliation; (ii) dates of Nativity and Lent fasts (the latter varies slightly from year to year); (iii) rural versus urban residence; (iv) length of day-light; (v) non-working days and (vi) trend. The models are tested for validity using analysis of variance while the regression coefficients are tested by the Student t-test.
  
  
  RESULTS
  All models are statistically valid (P < 0.01); all regression coefficients for the ORTHD group are valid (P < 0.01, except for rurality between 1990 and 2001, with P < 0.05). The data analysis indicates smaller standard error bars on the parameters for the ORTHD group as compared with the NORTHD group. The conclusion is that religious affiliation is an important factor in date of conception.
  
  
  CONCLUSIONS
  The data do not refer to all births during the analyzed period, but only to those persons still alive at the 1992 and 2002 censuses. The date of conception was estimated assuming 280 days for gestation, which is a medically accepted time interval but will undoubtedly vary. However, the primary independent variables (Lent and Nativity fast at 48 and 40 days, respectively) are long enough to overlap the uncertainty in the conception date following the sexual intercourse event. We also must assume that the religious affiliation of the parents is well defined, based on the information given by their offspring at census time, and is the same for both parents.
  
  
  CONCLUSIONS
  Our findings are consistent with other studies, which show differences between religious groups on date of conception, although we reach different conclusions regarding the influence of weather on fertility in Romania.
  
  
  BACKGROUND
  B.V.I., M.A. and G.R. have no competing interests to declare. There is no connection to the current paper, but C.H. declares that (i) he is currently conducting a research titled 'Chronic Diseases' Direct Costs within the Romanian Health System' funded by Local American Working Group; (ii) his wife is employed to a Romanian company (A&D Pharma) that does business in the pharmaceutical sector. This paper is a part of G.R. and M.A. scientific activities in COST Action TD1210. This work by C.H. was co-financed by the European Social Fund through project number POSDRU/1.5/S/59184.
authors.affiliation: Department of Statistics and Econometrics, Bucharest University of Economic Studies, Bucharest, Romania hertz@csie.ase.ro claudiu.herteliu@gmail.com.
authors.forename: Claudiu
authors.initials: C
authors.lastname: Herteliu
authors.affiliation: Department of Statistics and Econometrics, Bucharest University of Economic Studies, Bucharest, Romania.
authors.forename: Bogdan Vasile
authors.initials: BV
authors.lastname: Ileanu
authors.affiliation: School of Management, University of Leicester, Leicester, UK eHumanities Group, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands GRAPES, Angleur, Belgium.
authors.forename: Marcel
authors.initials: M
authors.lastname: Ausloos
authors.affiliation: Department of Methods and Models for Economics, Territory and Finance, Sapienza University of Rome, Rome, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Rotundo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D033003:Eastern Orthodoxy; D005260:Female; D005306:Fertilization; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D010507:Periodicity; D012042:Registries / Q000706:statistics & numerical data*; D012383:Romania; D055815:Young Adult
keywords: Eastern Orthodox; Lent; Nativity fast; date of conception; religion