1. Maternal age (years).
| Study ID | Omega‐3 (mean (SD)unless otherwise reported) | No omega‐3 (mean (SD)unless otherwise reported) |
| Ali 2017 | 27 (4.3) | 27 (4.8) |
| Bergmann 2007 | 30.9 (4.6) for DHA/FOS group | 30.0 (4.62) in vitamin/mineral group; 31 (4.71) for FOS group |
| Bisgaard 2016; | 32.3 (4.3) | 32.2 (4.5) |
| Boris 2004 | "The three study groups were similar in baseline characteristics with regard to maternal age at delivery (data not shown)". | |
| Bosaeus 2015 | 31.4 (3.9) | 31.2 (4.0) |
| Bulstra‐Ramakers 1994 | Not reported | |
| Carlson 2013 | 25.3 (4.9) | 24.8 (4.7) |
| Chase 2015 | Not reported | |
| D'Almedia 1992 | "Ages ranged from 14‐40 years" | |
| de Groot 2004 | 30.0 (3.3) | 29.2 (3.8) |
| Dilli 2018 | 30.9 (5.3) | 32.7 (5.9) |
| Dunstan 2008 | 30.9 (3.7) | 32.6 (3.6) |
| England 1989 | Not reported | |
| Freeman 2008 | 31.0 (5.8) | 29.7 (6.2) |
| Furuhjelm 2009 | 31.1 (4.1) | 31.7 (3.9) |
| Giorlandino 2013 | 32.6 (4.6) | 32.2 (4.8) |
| Gustafson 2013 | 25.5 (4.3) | 25.6 (4.8) |
| Haghiac 2015 | 27 (5) | 27 (5) |
| Harper 2010 | Median (interquartile range): 28 (23 ‐ 32) | Median (interquartile range): 27 (24‐32) |
| Harris 2015 | In high‐dose group 24.5 (12.72); In low‐dose group 24.3 (12.72) |
27.0 (9.05) |
| Hauner 2012 | 31.9 (4.9) | 31.6 (4.5) |
| Helland 2001 | 28.6 (3.4) | 27.6 (3.2) |
| Horvaticek 2017 | 29.8 (5.5) | 29.6 (4.8) |
| Hurtado 2015 | 30.5 (4.8) | 29.9 (4.7) |
| Ismail 2016 | 27.17 (6.34) | 26.71 (5.66) |
| Jamilian 2016 | 30.1 (5.3) | 30.0 (5.5) |
| Jamilian 2017 | 30.7 (3.5) for omega‐3 group 31.2 (4.3) for omega‐3 + vitamin D group |
30.7 (4.1) for placebo group 31.5 (7.0) for vitamin D group |
| Judge 2007 | 23.9 (4.3) | 24.7 (4.8) |
| Judge 2014 | Not reported | |
| Kaviani 2014 | 26.33 (4.2) | 25.15 (4.2) |
| Keenan 2014 | Not reported | |
| Khalili 2016 | 25.9 (4.8) | 26.9 (4.5) |
| Knudsen 2006 | 28.4 for 0.1 g/day EPA + DHA group 28.7 for 0.3 g/day EPA + DHA group 28.4 for 0.7 g/day EPA + DHA group 28.9 for 1.4 g/day EPA + DHA group 28.8 for 2.8 g/day EPA + DHA group 28.8 for 2.2g/day ALA group |
28.5 for no treatment group |
| Krauss‐Etschmann 2007 | Median (range): 30.6 (20.1 ‐ 41.1) for DHA/EPA group Median (range): 31.1 (21.5 ‐ 40.1) for DHA/EPA+folate group |
Median (range): 31.1 (18.8 ‐ 40.8) for folate group Median (range): 31.1 (18.4 ‐ 40.3) for no treatment (placebo) group |
| Krummel 2016 | 27.9 (4.6) | 26.3 (5.0) |
| Laivuori 1993 | Median (IQR): 30.3 (24‐40) | Median (IQR): 30.2 (26‐32) in placebo group; 32.0 (23‐40) in primrose oil group |
| Makrides 2010 | 28.9 (5.7) | 28.9 (5.6) |
| Malcolm 2003 | Not reported | |
| Mardones 2008 | 25.06 (5.73) | 25.11 (7.45) |
| Martin‐Alvarez 2012 | Not reported | |
| Miller 2016 | 31.7 (4.4) | 31.2 (4.4) |
| Min 2014 | Median (range): 29 (18 ‐ 42) | Median (range): 29 (18 ‐ 44) |
| Min 2014 [diabetic women] | Median (range): 34 (20 ‐ 45) | Median (range): 37 (27‐45) |
| Min 2016 | Median (range): 31.0 (21.0 ‐ 41.0) | Median (range): 32.0 (21.0 ‐ 44.0) |
| Mozurkewich 2013 | 30.6 (4.5) in DHA rich fish oil group; 29.9 (5.0) in EPA rich fish oil group | 30.4 (5.9) |
| Mulder 2014 | 32.6 (4.04) | 33.4 (3.61) |
| Noakes 2012 | 29.5 (3.94) | 28.4 (4.69) |
| Ogundipe 2016 | Not reported | |
| Oken 2013 | Median (IQR): 32.6 (27.9 ‐ 35.9) advice group; 27.6 (24.5 ‐ 32.0) advice + gift card group |
Median (IQR): 32.4 (27.7 to 34.3) |
| Olsen 1992 | 29.4 (4.4) | olive oil group 29.7 (4.3); placebo/no oil group 29.1 (4.1) |
| Olsen 2000 |
Prophylactic trials PD trial 29.3 (4.87) IUGR trial 30 (4.64) PIH trial 30.3 (7.01) Twins trial 30.2 (6.18) Therapeutic trials Threat‐PE trial 32.1 (11.7) Susp‐IUGR trial 29.3 (7.88) |
Prophylactic trials PD trial 30.0 (6.22) IUGR trial 29.0 (3.93) PIH trial 28.9 (5.32) Twins trial 30.2 (6.35) Therapeutic trials Threat‐PE trial 32.9 (14.6) Susp‐IUGR trial 29.8 (10.3) |
| Olsen 2000 [twins] | see Olsen 2000 | |
| Onwude 1995 | Mean (range): 26.6 (18‐39) | Mean (range): 26.1 (16‐40) |
| Otto 2000 | 30.3 (5.2) | 28.3 (4.85) |
| Pietrantoni 2014 | 30.86 (4.18) | 29.92 (4.80) |
| Ramakrishnan 2010 | 26.2 (4.6) | 26.3 (4.8) |
| Ranjkesh 2011 | 30.06 (7.59) | 28.96 (6.40) |
| Razavi 2017 | 29.7 (3.6) for omega‐3 group 29.9 (4.0) for omega‐3 + vitamin D group |
29.2 (3.4) for placebo group 29.9 (5.0) for vitamin D group |
| Rees 2008 | 31.2 (4.4) | 34.5 (3.8) |
| Ribeiro 2012 | Not reported | |
| Rivas‐Echeverria 2000 | Not reported | |
| Samimi 2015 | Median (range): 26.8 (18‐39) | Median (range): 26.1 (16‐40) |
| Sanjurjo 2004 | 34.5 (7.41) | 31.25 (5.18) |
| Smuts 2003a | 21.7 (4.3) | 21.6 (4.2) |
| Smuts 2003b | High DHA egg group 19.9 (4.1) | Ordinary egg group 24.8 (7.8) |
| Su 2008 | 30.9 (3.9) | 31.3 (5.7) |
| Taghizadeh 2016 | 28.6 (6.3) | 29.4 (4.4) |
| Tofail 2006 | 22.1 (4.2) | 23.4 (4.5) |
| Valenzuela 2015 | 29 (4.7) | 28.3 (6.7) |
| Van Goor 2009 | Median (range): 32.3 (22.3 ‐ 43.3) in DHA group; 31.5 (24.8 ‐ 41.4) in DHA + AA group |
Median (range): 33.5 (26.0 ‐ 40.3) |
| Van Winden 2017 | Not reported | |
| Vaz 2017 | Median (IQR): 25.5 (22.0‐34.5) | Median (IQR): 27.0 (21.0 ‐ 31.0) |
Abbreviations: IQR (interquartile range)