R. Ajrouche, J. Rudant, L. Orsi, A. Petit, A. Baruchel et al., Maternal reproductive history, fertility treatments and folic acid supplementation in the risk of childhood acute leukemia: the ESTELLE Study, Cancer Causes & Control, vol.86, issue.10, 2014.
DOI : 10.1007/s10552-014-0429-8
URL : https://hal.archives-ouvertes.fr/hal-01064579

A. Altieri, F. Castro, J. Bermejo, and K. Hemminki, Number of Siblings and the Risk of Lymphoma, Leukemia, and Myeloma by Histopathology, Cancer Epidemiology Biomarkers & Prevention, vol.15, issue.7, pp.1281-1287, 2006.
DOI : 10.1158/1055-9965.EPI-06-0087

B. Blondel, N. Lelong, M. Kermarrec, and F. Goffinet, Trends in perinatal health in France from 1995 to 2010. Results from the French National Perinatal Surveys, Journal de Gyn??cologie Obst??trique et Biologie de la Reproduction, vol.41, issue.4, pp.1-15, 2012.
DOI : 10.1016/j.jgyn.2012.04.014
URL : https://hal.archives-ouvertes.fr/inserm-00857949

I. Bross and R. Gibson, Cats and childhood leukemia, J Med, vol.1, issue.3, pp.180-187, 1970.

J. Buckley, C. Buckley, K. Ruccione, H. Sather, M. Waskerwitz et al., Epidemiological characteristics of childhood acute lymphocytic leukemia. Analysis by immunophenotype. The Childrens Cancer Group, Leukemia, vol.8, issue.5, pp.856-64, 1994.

P. Campo, H. Kalra, L. Levin, T. Reponen, R. Olds et al., Influence of dog ownership and high endotoxin on wheezing and atopy during infancy, Journal of Allergy and Clinical Immunology, vol.118, issue.6, pp.1271-1279, 2006.
DOI : 10.1016/j.jaci.2006.08.008

C. Cardwell, P. Mckinney, C. Patterson, and L. Murray, Infections in early life and childhood leukaemia risk: a UK case???control study of general practitioner records, British Journal of Cancer, vol.350, issue.9, pp.1529-1562, 2008.
DOI : 10.1038/sj.bjc.6604696

L. Chan, T. Lam, C. Li, Y. Lau, H. Yuen et al., Is the timing of exposure to infection a major determinant of acute lymphoblastic leukaemia in Hong Kong?, Paediatric and Perinatal Epidemiology, vol.307, issue.2, pp.154-65, 2002.
DOI : 10.1054/bjoc.1999.0905

J. Chang, C. Tsai, Y. Tsai, and J. Wiemels, Medically diagnosed infections and risk of childhood leukaemia: a population-based case-control study, International Journal of Epidemiology, vol.41, issue.4, 2012.
DOI : 10.1093/ije/dys113

J. Chang, M. Zhou, P. Buffler, A. Chokkalingam, C. Metayer et al., Profound Deficit of IL10 at Birth in Children Who Develop Childhood Acute Lymphoblastic Leukemia, Cancer Epidemiology Biomarkers & Prevention, vol.20, issue.8, pp.1736-1740, 2011.
DOI : 10.1158/1055-9965.EPI-11-0162

G. Chirico, R. Marzollo, S. Cortinovis, C. Fonte, and A. Gasparoni, Antiinfective properties of human milk, Journal of Nutrition, vol.138, issue.9, pp.1801-1806, 2008.

S. Crouch, T. Lightfoot, J. Simpson, A. Smith, P. Ansell et al., Infectious Illness in Children Subsequently Diagnosed With Acute Lymphoblastic Leukemia: Modeling the Trends From Birth to Diagnosis, American Journal of Epidemiology, vol.176, issue.5, pp.402-410, 2012.
DOI : 10.1093/aje/kws180

J. Dockerty, G. Draper, T. Vincent, S. Rowan, and K. Bunch, Case-control study of parental age, parity and socioeconomic level in relation to childhood cancers, International Journal of Epidemiology, vol.30, issue.6, pp.1428-1465, 2001.
DOI : 10.1093/ije/30.6.1428

J. Dockerty, D. Skegg, J. Elwood, G. Herbison, D. Becroft et al., Infections, vaccinations, and the risk of childhood leukaemia, British Journal of Cancer, vol.80, issue.9, pp.1483-1492, 1999.
DOI : 10.1038/sj.bjc.6690548

R. Enserink, H. Noel, I. Friesema, C. De-jager, A. Kooistra-smid et al., Sentinel Surveillance Network I (2012) The KIzSS network, a sentinel surveillance system for infectious diseases in day care centers: study protocol, Bmc Infectious Diseases, vol.12

L. Fernandez, S. Langa, V. Martin, A. Maldonado, E. Jimenez et al., The human milk microbiota: Origin and potential roles in health and disease, Pharmacological Research, vol.69, issue.1, pp.1-10, 2013.
DOI : 10.1016/j.phrs.2012.09.001

A. Ford, C. Palmi, C. Bueno, D. Hong, P. Cardus et al., The TEL-AML1 leukemia fusion gene dysregulates the TGF-beta pathway in early B lineage progenitor cells, J Clin Invest, vol.119, issue.4, pp.826-862, 2009.

S. Francis, S. Selvin, C. Metayer, A. Wallace, V. Crouse et al., Mode of Delivery and Risk of Childhood Leukemia, Cancer Epidemiology Biomarkers & Prevention, vol.23, issue.5, pp.876-81, 2014.
DOI : 10.1158/1055-9965.EPI-13-1098

C. Gilham, J. Peto, J. Simpson, E. Roman, T. Eden et al., Day care in infancy and risk of childhood acute lymphoblastic leukaemia: findings from UK case-control study, BMJ, vol.330, issue.7503, p.1294, 2005.
DOI : 10.1136/bmj.38428.521042.8F

M. Greaves, Infection, immune responses and the aetiology of childhood leukaemia, Nature Reviews Cancer, vol.76, issue.2, pp.193-203, 2006.
DOI : 10.1038/nrc1816

M. Greaves, Speculations on the cause of childhood acute lymphoblastic leukemia, Leukemia, vol.2, issue.2, pp.120-125, 1988.

M. Gronlund, O. Lehtonen, E. Eerola, and P. Kero, Fecal Microflora in Healthy Infants Born by Different Methods of Delivery: Permanent Changes in Intestinal Flora After Cesarean Delivery, Journal of Pediatric Gastroenterology & Nutrition, vol.28, issue.1, pp.19-25, 1999.
DOI : 10.1097/00005176-199901000-00007

L. Hjalgrim, K. Rostgaard, H. Hjalgrim, T. Westergaard, H. Thomassen et al., Birth Weight and Risk for Childhood Leukemia in Denmark, Sweden, Norway, and Iceland, JNCI Journal of the National Cancer Institute, vol.96, issue.20, pp.1549-56, 2004.
DOI : 10.1093/jnci/djh287

C. Infante-rivard, I. Fortier, and E. Olson, Markers of infection, breast-feeding and childhood acute lymphoblastic leukaemia, British Journal of Cancer, vol.83, issue.11, pp.1559-64, 2000.
DOI : 10.1054/bjoc.2000.1495

C. Infante-rivard and S. Weichenthal, Pesticides and Childhood Cancer: An Update of Zahm and Ward's 1998 Review, Journal of Toxicology and Environmental Health, Part B, vol.1, issue.1-2, pp.81-99, 2007.
DOI : 10.2307/3434207

K. Johnson, J. Soler, S. Puumala, J. Ross, and L. Spector, Parental and infant characteristics and childhood leukemia in Minnesota, BMC Pediatrics, vol.6, issue.3, p.7, 2008.
DOI : 10.1023/A:1019726112597

J. Silva, N. Perel, Y. Mechinaud, F. Plouvier, E. Gandemer et al., Infectious diseases in the first year of life, perinatal characteristics and childhood acute leukaemia, British Journal of Cancer, vol.90, issue.1, pp.139-184, 2004.
DOI : 10.1038/sj.bjc.6601384
URL : https://hal.archives-ouvertes.fr/inserm-00086434

M. Kamper-jorgensen, C. Benn, and J. Wohlfahrt, Childcare and health: A review of using linked national registers, Scandinavian Journal of Public Health, vol.39, issue.7 Suppl, pp.126-130, 2011.
DOI : 10.1177/1403494810395826

M. Kamper-jorgensen, A. Woodward, J. Wohlfahrt, C. Benn, J. Simonsen et al., Childcare in the first 2 years of life reduces the risk of childhood acute lymphoblastic leukemia, Leukemia, vol.160, issue.1, pp.189-93, 2008.
DOI : 10.1038/sj.leu.2404884

S. Kaye, L. Robison, W. Smithson, P. Gunderson, F. King et al., Maternal reproductive history and birth characteristics in childhood acute lymphoblastic leukemia, Cancer, vol.4, issue.6, pp.1351-1356, 1991.
DOI : 10.1002/1097-0142(19910915)68:6<1351::AID-CNCR2820680627>3.0.CO;2-J

L. Kinlen, An examination, with a meta-analysis, of studies of childhood leukaemia in relation to population mixing, British Journal of Cancer, vol.90, issue.7, pp.1163-1171, 2012.
DOI : 10.1093/aje/kwh099

M. Kwan, P. Buffler, B. Abrams, and V. Kiley, Breastfeeding and the Risk of Childhood Leukemia: A Meta-Analysis, Public Health Reports, vol.5, issue.6, pp.521-556, 2004.
DOI : 10.2307/2533446

M. Kwan, P. Buffler, J. Wiemels, C. Metayer, S. Selvin et al., Breastfeeding patterns and risk of childhood acute lymphoblastic leukaemia, British Journal of Cancer, vol.354, issue.3, pp.379-84, 2005.
DOI : 10.1038/sj.bjc.6602706

B. Lacour, A. Guyot-goubin, S. Guissou, S. Bellec, E. Desandes et al., Incidence of childhood cancer in France: National Children Cancer Registries, 2000???2004, European Journal of Cancer Prevention, vol.19, issue.3, pp.173-81, 2000.
DOI : 10.1097/CEJ.0b013e32833876c0

B. Lacour, A. Guyot-goubin, S. Guissou, S. Bellec, E. Desandes et al., Incidence of childhood cancer in France: National Children Cancer Registries, 2000???2004, European Journal of Cancer Prevention, vol.19, issue.3, pp.173-81, 2000.
DOI : 10.1097/CEJ.0b013e32833876c0

Y. Lee and S. Mazmanian, Has the Microbiota Played a Critical Role in the Evolution of the Adaptive Immune System?, Science, vol.330, issue.6012, pp.1768-73, 2010.
DOI : 10.1126/science.1195568

N. Lu, M. Samuels, L. Shi, S. Baker, S. Glover et al., Child day care risks of common infectious diseases revisited, Child: Care, Health and Development, vol.87, issue.4, pp.361-368, 2004.
DOI : 10.1111/j.1365-2214.2004.00411.x

X. Ma, P. Buffler, J. Wiemels, S. Selvin, C. Metayer et al., Ethnic Difference in Daycare Attendance, Early Infections, and Risk of Childhood Acute Lymphoblastic Leukemia, Cancer Epidemiology Biomarkers & Prevention, vol.14, issue.8, pp.1928-1962, 2005.
DOI : 10.1158/1055-9965.EPI-05-0115

X. Ma, K. Urayama, J. Chang, J. Wiemels, and P. Buffler, Infection and pediatric acute lymphoblastic leukemia, Blood Cells, Molecules, and Diseases, vol.42, issue.2, pp.117-120, 2009.
DOI : 10.1016/j.bcmd.2008.10.006

A. Macarthur, M. Mcbride, J. Spinelli, S. Tamaro, R. Gallagher et al., Risk of Childhood Leukemia Associated with Vaccination, Infection, and Medication Use in Childhood: The Cross-Canada Childhood Leukemia Study, American Journal of Epidemiology, vol.167, issue.5, pp.598-606, 2008.
DOI : 10.1093/aje/kwm339

J. Madan, S. Farzan, P. Hibberd, and M. Karagas, Normal neonatal microbiome variation in relation to environmental factors, infection and allergy, Current Opinion in Pediatrics, vol.24, issue.6, pp.753-762, 2012.
DOI : 10.1097/MOP.0b013e32835a1ac8

R. Martin, D. Gunnell, C. Owen, and G. Smith, Breast-feeding and childhood cancer: A systematic review with metaanalysis, International Journal of Cancer, vol.9, issue.6, pp.1020-1051, 2005.
DOI : 10.1002/ijc.21274

P. Mckinney, E. Juszczak, E. Findlay, K. Smith, and C. Thomson, Pre- and perinatal risk factors for childhood leukaemia and other malignancies: a Scottish case control study, British Journal of Cancer, vol.80, issue.11, pp.1844-51, 1999.
DOI : 10.1038/sj.bjc.6690609

L. Murray, P. Mccarron, K. Bailie, R. Middleton, D. Smith et al., Association of early life factors and acute lymphoblastic leukaemia in childhood: historical cohort study, British Journal of Cancer, vol.131, issue.3, pp.356-61, 2002.
DOI : 10.1038/sj.bjc.6600012

E. Naumburg, R. Bellocco, S. Cnattingius, A. Jonzon, and A. Ekbom, Perinatal exposure to infection and risk of childhood leukemia, Medical and Pediatric Oncology, vol.17, issue.6, pp.391-398, 2002.
DOI : 10.1002/mpo.10084

J. Neglia, M. Linet, X. Shu, R. Severson, J. Potter et al., Patterns of infection and day care utilization and risk of childhood acute lymphoblastic leukaemia, Br J Cancer, vol.82, issue.1, pp.234-274, 2000.

M. Nesti and M. Goldbaum, Infectious diseases and daycare and preschool education, Jornal de Pediatria, vol.83, issue.4, 2007.
DOI : 10.2223/JPED.1649

C. Nicholas, G. Wegienka, S. Havstad, D. Ownby, C. Johnson et al., How Accurately Do Young Adults Recall Childhood Pets? A Validation Study, American Journal of Epidemiology, vol.170, issue.3, pp.388-92, 2009.
DOI : 10.1093/aje/kwp139

M. Nishi and H. Miyake, A case-control study of non-T cell acute lymphoblastic leukaemia of children in Hokkaido, Japan., Journal of Epidemiology & Community Health, vol.43, issue.4, pp.352-357, 1989.
DOI : 10.1136/jech.43.4.352

M. Okcu, K. Goodman, S. Carozza, N. Weiss, K. Burau et al., Birth weight, ethnicity, and occurrence of cancer in children: a population-based, incident case-control study in the State of Texas, Cancer Causes and Control, vol.13, issue.7, pp.595-602, 2002.
DOI : 10.1023/A:1019555912243

S. Oksuzyan, C. Crespi, M. Cockburn, G. Mezei, and L. Kheifets, Birth weight and other perinatal characteristics and childhood leukemia in California, Cancer Epidemiology, vol.36, issue.6, pp.359-65, 2012.
DOI : 10.1016/j.canep.2012.08.002

S. Ou, D. Han, R. Severson, Z. Chen, J. Neglia et al., Birth characteristics, maternal reproductive history, hormone use during pregnancy, and risk of childhood acute lymphocytic leukemia by immunophenotype, 2002.

F. Perrillat, J. Clavel, M. Auclerc, A. Baruchel, G. Leverger et al., Day-care, early common infections and childhood acute leukaemia: a multicentre French case???control study, British Journal of Cancer, vol.86, issue.7, pp.1064-1073, 2002.
DOI : 10.1038/sj.bjc.6600091
URL : https://hal.archives-ouvertes.fr/inserm-00137620

E. Petridou, M. Dalamaga, A. Mentis, A. Skalkidou, M. Moustaki et al., Evidence on the infectious etiology of childhood leukemia: the role of low herd immunity (Greece), Cancer Causes and Control, vol.12, issue.7, pp.645-52, 2001.
DOI : 10.1023/A:1011255825887

E. Petridou, D. Kassimos, M. Kalmanti, H. Kosmidis, S. Haidas et al., Age of exposure to infections and risk of childhood leukaemia., BMJ, vol.307, issue.6907, p.774, 1993.
DOI : 10.1136/bmj.307.6907.774

E. Petridou, D. Trichopoulos, V. Kalapothaki, A. Pourtsidis, M. Kogevinas et al., The risk profile of childhood leukaemia in Greece: a nationwide case-control study, British Journal of Cancer, vol.76, issue.9, pp.1241-1248, 1997.
DOI : 10.1038/bjc.1997.541

D. Podvin, C. Kuehn, B. Mueller, and M. Williams, Maternal and birth characteristics in relation to childhood leukaemia, Paediatric and Perinatal Epidemiology, vol.62, issue.4, pp.312-334, 2006.
DOI : 10.1080/080352500750028041

P. Reynolds, V. Behren, J. Elkin, and E. , Birth Characteristics and Leukemia in Young Children, American Journal of Epidemiology, vol.155, issue.7, pp.603-616, 2002.
DOI : 10.1093/aje/155.7.603

E. Roman, J. Simpson, A. P. Kinsey, S. Mitchell, C. Mckinney et al., Childhood Acute Lymphoblastic Leukemia and Infections in the First Year of Life: A Report from the United Kingdom Childhood Cancer Study, American Journal of Epidemiology, vol.165, issue.5, pp.496-504, 2007.
DOI : 10.1093/aje/kwk039

P. Rosenbaum, G. Buck, and M. Brecher, Early Child-Care and Preschool Experiences and the Risk of Childhood Acute Lymphoblastic Leukemia, American Journal of Epidemiology, vol.152, issue.12, pp.1136-1180, 2000.
DOI : 10.1093/aje/152.12.1136

P. Rosenbaum, G. Buck, and M. Brecher, Allergy and infectious disease histories and the risk of childhood acute lymphoblastic leukaemia, Paediatric and Perinatal Epidemiology, vol.11, issue.2, pp.152-64, 2005.
DOI : 10.1111/j.1365-3016.2005.00634.x

J. Round and S. Mazmanian, The gut microbiota shapes intestinal immune responses during health and disease, Nature Reviews Immunology, vol.65, issue.5, pp.313-336, 2009.
DOI : 10.1038/nri2515

J. Rudant, Childhood Acute Lymphoblastic Leukemia and Indicators of Early Immune Stimulation: A Childhood Leukemia International Consortium Study, American Journal of Epidemiology, vol.181, issue.8, 2014.
DOI : 10.1093/aje/kwu298

J. Rudant, L. Orsi, F. Menegaux, A. Petit, A. Baruchel et al., Childhood Acute Leukemia, Early Common Infections, and Allergy: The ESCALE Study, American Journal of Epidemiology, vol.172, issue.9, pp.1015-1027, 2010.
DOI : 10.1093/aje/kwq233

J. Schuz, U. Kaletsch, R. Meinert, P. Kaatsch, and J. Michaelis, Association of childhood leukaemia with factors related to the immune system, British Journal of Cancer, vol.80, issue.3-4, pp.3-4, 1999.
DOI : 10.1038/sj.bjc.6690395

R. Siggers, T. Thymann, B. Jensen, L. Molbak, P. Heegaard et al., Elective cesarean delivery affects gut maturation and delays microbial colonization but does not increase necrotizing enterocolitis in preterm pigs, AJP: Regulatory, Integrative and Comparative Physiology, vol.294, issue.3, pp.929-967, 2008.
DOI : 10.1152/ajpregu.00705.2007

J. Simpson, A. Smith, P. Ansell, and E. Roman, Childhood leukaemia and infectious exposure: A report from the United Kingdom Childhood Cancer Study (UKCCS), European Journal of Cancer, vol.43, issue.16, pp.2396-403, 2007.
DOI : 10.1016/j.ejca.2007.07.027

A. Swensen, J. Ross, X. Shu, G. Reaman, M. Steinbuch et al., Pet ownership and childhood acute leukemia (USA and Canada), Cancer Causes and Control, vol.12, issue.4, pp.301-304, 2001.
DOI : 10.1023/A:1011276417369

M. Taylor, A. Hussain, K. Urayama, A. Chokkalingam, P. Thompson et al., The human major histocompatibility complex and childhood leukemia: An etiological hypothesis based on molecular mimicry, Blood Cells, Molecules, and Diseases, vol.42, issue.2, pp.129-164, 2009.
DOI : 10.1016/j.bcmd.2008.10.009

K. Urayama, P. Buffler, E. Gallagher, J. Ayoob, and X. Ma, A meta-analysis of the association between day-care attendance and childhood acute lymphoblastic leukaemia, International Journal of Epidemiology, vol.39, issue.3, pp.718-732, 2010.
DOI : 10.1093/ije/dyp378

K. Urayama, X. Ma, and P. Buffler, Exposure to infections through day-care attendance and risk of childhood leukaemia, Radiation Protection Dosimetry, vol.132, issue.2, pp.259-66, 2008.
DOI : 10.1093/rpd/ncn271

K. Urayama, X. Ma, S. Selvin, C. Metayer, A. Chokkalingam et al., Early life exposure to infections and risk of childhood acute lymphoblastic leukemia, International Journal of Cancer, vol.38, issue.7, pp.1632-1643, 2011.
DOI : 10.1002/ijc.25752

H. Van-steensel-moll, H. Valkenburg, and G. Van-zanen, CHILDHOOD LEUKEMIA AND INFECTIOUS DISEASES IN THE FIRST YEAR OF LIFE: A REGISTER-BASED CASE-CONTROL STUDY, American Journal of Epidemiology, vol.124, issue.4, pp.590-594, 1986.
DOI : 10.1093/oxfordjournals.aje.a114431

T. Vestergaard, K. Rostgaard, K. Grau, K. Schmiegelow, and H. Hjalgrim, Hospitalisation for infection prior to diagnosis of acute lymphoblastic leukaemia in children, Pediatric Blood & Cancer, vol.157, issue.3, pp.428-432, 2013.
DOI : 10.1002/pbc.24286

J. Wiemels, Perspectives on the causes of childhood leukemia, Chemico-Biological Interactions, vol.196, issue.3, pp.59-67, 2012.
DOI : 10.1016/j.cbi.2012.01.007

A. Acute, ALL: acute lymphoblastic leukaemia; CI: confidence interval; OR: odds ratio ?ORs and 95%CI estimated by unconditional logistic regression adjusted for age, gender, parental category, degree of urbanisation b Ear-nose-throat surgery (tonsillectomy, adenoidectomy, paracenteses)