Table 1.
Characteristics of Studies Included in the Meta-Analysis
| Week of B12 measurement | Included in specific meta-analysesa | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Study | Data | n | Country | Study years | B12 analysis method | Range | Median | Birth weight | LBW | SGA | Birth weight SD score | Length of gestation | Preterm birth |
| Baker, 2009 (18) | IPD | 290 | The United Kingdom | 2004-2007 | RIA | 27-43 | 30 | x | x | x | x | x | x |
| Bergen, 2012 (19) | IPD | 5,641 | The Netherlands | 2002-2006 | ECL | 5-18 | 13 | x | x | x | x | x | x |
| Bhate, 2012 (20) | Reanalysed data | 214 | India | 2004-2006 | Micro-biological | 24-30 | 28 | x | x | x | x | ||
| Chen, 2015 (21) | IPD | 988 | Singapore | 2009-2010 | ECL | 26-29 | 27 | x | x | x | x | x | x |
| Dayaldasani, 2014 (22) | IPD | 187 | Spain | 2011 | ECL | 3-23 | 10 | xb | xb | xb | xb | xb | xb |
| Dwarkanath, 2013 (23) | IPD | 344 | India | 2001-2003 | ECL | T1: 5-19 T2: 20-29 T3: 30-39 |
T1: 12 T2: 24 T3: 34 |
x | x | x | x | x | x |
| Furness, 2013 (24) | Data from publication | 84 | Australia | NA | ECL | 18-20 | NA | xc | |||||
| Halicioglu, 2012 (25) | Data from publication | 208 | Turkey | 2008 | ECL | >37 | NA | xd | |||||
| Hay, 2010 (26) | IPD | 149 | Norway | 1997 | Micro-biological | 17-19 | NA | x | |||||
| Hogeveen, 2010 (27) | IPD | 363 | The Netherlands | 2002-2004 | Micro-biological | 27-38 | 31 | xe | xe | xe | xe | xe | xe |
| Kaymaz, 2011 (28) | IPD | 103 | Turkey | 2007 | ECL | 11-14 | 13 | x | x | x | x | ||
| Krishnaveni, 2014 (29) | IPD | 654 | India | 1997-1998 | Micro-biological | 22-35 | 26 | x | x | x | x | x | x |
| Mamabolo, 2006 (30) | Data from publication | 219 | South Africa | 1999-2000 | RIA | 28-36 | NA | xc | |||||
| Relton, 2005 (31) | Data from publication | 500 | The United Kingdom | 2000-2002 | RIA | NA | 11.5 (5.8)f | xe | |||||
| Sukumar, 2011 (32) | IPD | 209 | The United Kingdom | 2005-2010 | RIA (n=182), ECL (n=27) | 0-37 | 24 | x | x | x | x | x | x |
| Takimoto, 2007 (33) | Data from publication | 88 | Japan | 2001-2003 | ECL | T1: 7-14 T3: 34-36 |
T1: NA T3: NA |
xg | |||||
| Wu, 2013 (34) | Data from publication | 216 | Canada | NA | RIA | NA | 36 | xd | |||||
| Yajnik, 2008 (35) | Reanalysed data | 759 | India | 1994-1996 | Micro-biological | NA | T2: 18 (2)f | x | x | x | x | ||
Studies are referred to according to their citation number in the text. ECL, electroluminescence; IPD, individual participant data; n, number of pregnancies; NA, not available; RIA, radioimmunoassay; SD, standard deviation; SGA, small-for-gestational-age; T1, 1st trimester; T2, 2nd trimester; T3, 3rd trimester.
included in the analyses of the exposures B12 SD score and B12-deficiency, both crude and adjusted (maternal age, body mass index or weight, and parity), if not otherwise specified;
does not contribute in the analyses of B12-deficiency (none of the participants were deficient);
level of B12 in SGA versus non-SGA, crude analysis;
birth weight among B12-deficient versus non-deficient, crude analysis;
crude analysis;
mean (SD);
adjusted analysis (maternal age, body mass index or weight, and parity).