Vrijheid et al. A Microsoft Access database was constructed to contain the responses from the cohorts. All cohorts were asked to check this database for errors before making it public. The last correc- tions and updates were made in February 2011. A Web-based searchable inventory is now pub- licly available on www.birthcohortsenrieco.net (ENRIECO 2011) and also accessible through www.birthcohorts.net (Birthcohorts.net 2010). Results A total of 46 birth cohort studies were iden- tified as potentially eligible based on publi- cations, Web sites, and word of mouth. Six of these were excluded after completion of questionnaires, because they did not match the eligibility criteria: Three did not assess envi- ronmental exposures, and three did not have a follow-up point after birth. Another three birth cohorts did not return the questionnaires (Table 1). The 37 included cohorts, totaling > 350,000 study subjects, are situated in 19 European countries, principally in Northern and Western Europe (Figure 1). Five of the cohorts are in Eastern Europe and seven in Southern Europe (based on the European regions classified in the United Nations geoscheme). Twenty-five of the 37 cohorts defined themselves as regionally based stud- ies, six as nationally based, four as hospital Pregnancy 1–6 6–18 18 mo– Cohort Start T1 T2 T3 Birth mo mo 5 year 5–10 year ≥ 10 year 1985 Leicester I Faroes 1 1986 MAS 1990 ALSPAC 1991 Leicester II 1993 BAMSE 1994 Faroes 2 1994 Czech 1994 GINIplus 1995 DNBC 1996 PIAMA 1996 Faroes 3 1997 INMA old 1997 LISAplus 1997 DARC 1998 MoBa 1999 Duisburg 2000 KOALA 2000 Kraków 2000 Generation R 2001 PCB cohort 2001 FLEHS I 2002 HUMIS 2002 INUENDO 2002 LUKAS 2002 PÉLAGIE 2002 ABCD 2003 EDEN 2003 GASPII 2003 PARIS 2003 Co.N.ER 2004 Generation XXI 2004 INMA new 2004 NINFEA 2005 ArcRisk-Norway 2007 BiB 2007 Faroes 5 2007 KANC 2007 REPRO_PL 2007 RHEA 2007 ELFE 2011 based, and two as studying selected popula- tions [farmers in the LUKAS cohort and high- risk allergic children in the Multicentre Allergy Study (MAS)]. Two studies, the Danish National Birth Cohort (DNBC) and the Norwegian Mother and Child Study (MoBa) have recruited around 100,000 mother– child pairs each (Table 1). Ten cohorts have recruited between 5,000 and 20,000 pairs, 18 between 1,000 and 5,000 pairs, and seven cohorts concern < 1,000 pairs. At our reference date (February 2011), children in 19 cohorts were between 5 and 10 years of age, children in 12 cohorts were > 10 years of age, and in five cohorts they were < 5 years of age. One cohort in France, Etude Longitudinale Française depuis l’Enfance (ELFE), started data collection in April 2011. Most of the cohorts started recruit- ment of mothers during pregnancy (n = 25); the remaining started at birth. Most cohorts have multiple follow-up points after birth, and the majority have follow-up points in each of the child age periods specified in the questionnaire (1–6 months, 6–18 months, 18 months–5 years, 5–10 years, > 10 years) (Figure 2). Biological samples were collected in all cohorts from the mother and/or the child and, more rarely, from the father (Table 2). Sampling covered prenatal and postnatal periods and many types of tissue, including blood, urine, hair, nails, breast milk, placentas, and saliva. All but six cohorts [The Stockholm Children Allergy and Environmental Prospective Birth Cohort Study (BAMSE); German Infant Nutritional Intervention Study—plus influence of pollution and genetics on allergy develop- ment (GINIplus); The Leicester Respiratory Cohorts (Leicester); Birth and Infancy: Effects of the Environment (NINFEA); Pollution and Asthma Risk: An Infant Study (PARIS); Prevention and Incidence of Asthma and Mite Allergy (PIAMA)] collected, or plan to collect, blood samples from the mother during preg- nancy or cord blood at birth. Many cohort studies collected informa- tion on passive smoking (n = 36), maternal occupation (n = 33), outdoor air pollution (n = 27), and allergens/biological organisms (n = 27) (Table 3). Fewer cohorts have col- lected information on water contamination (n = 13), ionizing or nonionizing radiation exposures (n = 12), noise (n = 14), or emerg- ing chemical exposures such as phthalates and bisphenol A (n = 17). Details of each assessment (methods, numbers of subjects, and time period of assessment) can be found in the Web inventory (ENRIECO 2011). Twenty-seven cohorts have measured or are measuring contaminants or their metabolites as markers of internal dose, mostly in the cat- egories of metals, persistent organic pollut- ants, and tobacco smoke (Table 4). Figure 2. Start of enrollment and time points of follow-upa (vertical bars) in European birth cohorts collabo- rating in ENRIECO. T1, T2, and T3 are first, second, and third trimesters. mo, months. See Table 1 for full names and locations of cohorts. aThese are points in predefined periods. Some cohorts have many more (e.g., yearly) follow-points not reflected in this figure. The four Faroes cohorts and the two Leicester cohorts are shown separately because they have different time lines. 32 ovlume 120 | number 1 | January 2012 • Environmental Health Perspectives