Table 1. Characteristics of included studies in the meta-analysis.
| First Author | Year | Country | Study types and description | Total cases/controls | Risk Factors |
|---|---|---|---|---|---|
| Zakaria | 2013 | Egypt | Nested case-control study with 1 year follow-up. | 29/40 | Maternal smoking, diabetes. |
| Brouwers | 2012 | Netherlands | Hospital based case-control study matched with geographical distribution and sex. | 200/629 | Maternal smoking, alcohol, diabetes, BMI. |
| Jensen1 | 2007 | Denmark | Cohort study with 3 years follow-up. | 270 cases | Maternal smoking. |
| Strandberg | 2009 | Denmark | Cohort study with 6 years follow-up. | 1,598 cases | Maternal alcohol. |
| Kurahashi | 2005 | Japan | Hospital-based case-control study matched with sex. | 96/116 | Maternal smoking, alcohol, BMI. |
| Adams | 2011 | America | Population-based case-control study matched with age and sex. | 2,759/35,268 | Gestational smoking, diabetes, obesity. |
| Berkowitz1 | 1996 | America | Nested case-control study with 3 years follow-up. | 69/219 | Maternal smoking, alcohol, diabetes, BMI. |
| Mori | 1992 | Japan | Hospital-based case-control study matched with age and sex. | 104/104 | Maternal smoking, alcohol. |
| Agopian | 2014 | America | Cohort study with 10 years follow-up. | 4,001 cases | Maternal diabetes. |
| Trabert | 2014 | America | Cohort study with 10 years follow-up. | 3,649 cases | Maternal diabetes. |
| Mongraw-C | 2007 | America | Cohort study with 8 yeas follow-up. | 101 cases | Maternal smoking, alcohol. |
| Damgaard1 | 2008 | Denmark | Cohort study with 2 to 4 years follow-up. | 128 cases | Maternal smoking, alcohol. |
| Fernandez | 2007 | Spain | Nested case-control study with about 2.5 years follow-up. | 47/105 | Maternal smoking, BMI. |
| McGlynn | 2006 | America | Cohort study with7 years follow-up. | 238 cases | Maternal smoking, diabetes. |
| Jones | 1998 | British | Cohort study with 17 years follow-up. | 1,499 cases | Maternal smoking, obesity, diabetes. |
| Giordano | 2008 | Italy | Population-based case-control study matched with age and sex and city. | 48/202 | Maternal smoking, alcohol. |
| Jensen2 | 2007 | Denmark | Cohort study with 3 years follow-up. | 270 cases | Maternal smoking, alcohol. |
| Virtanen | 2006 | Denmark, Finland | Hospital-based case-control study matched with age and sex. | 125 cases | Maternal smoking, gestational diabetes. |
| Pierik | 2004 | Netherlands | Nested case-control study with 2 years follow-up. | 78/313 | Maternal smoking. |
| Biggs | 2002 | America | Hospital-based case-control study matched with age and sex. | 2,395/9,580 | Maternal smoking, alcohol, diabetes. |
| Berkowitz2 | 1995 | America | Nested case-control study with 3 years follow-up | 231 cases | Maternal smoking, BMI. |
| Damgaard2 | 2008 | Denmark | Cohort study with 2 to 4 years follow-up. | 128 cases | Maternal smoking, BMI. |
| Akre | 1999 | Sweden | Hospital-based case-control study matched with age and hospital birth. | 2,782/13,916 | Maternal smoking. |
| Beard | 1984 | America | Case-control study matched with year of delivery, maternal age, gravidity, parity. | 81/159 | Maternal smoking. |
| Preiksa | 2005 | Lithuania | Cohort study with 1 year follow-up. | 69 cases | Maternal smoking. |
| Davies | 1986 | British | Hospital-based case-control study matched with age and hospital birth. | 83/129 | Maternal smoking, alcohol, diabetes. |
| Mcbirde | 1991 | British | Population-based case-control study matched with age and sex. | 244/488 | Maternal smoking, alcohol. |
| Carbone | 2006 | Italy | Population-based case-control study matched with age and city. | 48/203 | Maternal smoking, alcohol. |
| Wagner-Mahler | 2011 | France | Cohort study with 3 years follow-up. | 76/137 | Maternal smoking, alcohol drinking. |
| Shiono | 1986 | America | Cohort study with 3 years follow-up. | 233/424 | Maternal smoking. |
| Main! | 2007, 2008 | Denmark, Finland | Cohort study with 4 years follow-up. | 95/185 | Maternal smoking, alcohol, diabetes. |
Jensen1 and Jensen2, Berkowitz1 and Berkowitz2, Damgaard1 and Damgaard2 are three pairs of studies, and each pair was published by the same author; some of the data are the same, but different risk factors were evaluated.