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Table 1 Folate variables and maternal characteristics

From: Retracted: Folic acid supplementation, dietary folate intake during pregnancy and risk for spontaneous preterm delivery: a prospective observational cohort study

     Total folate intake (μg/d) Initiation of preconceptional folic acid supplementation, n (%)
   n (%) median (IQR) p1 >8 w 0-8 w no p2
Total   65668 (100) 266 (153–543)   15471 (24) 12308 (19) 37889 (58)  
  <25 7583 (12) 228 (143–504)   842 (11) 879 (12) 5862 (77)  
Maternal age 25-29 22745 (35) 275 (154–547) <0.0001 4990 (22) 4605 (20) 13150 (58) <0.0001
in years 30-34 27782 (42) 270 (155–546)   7475 (27) 5662 (20) 14645 (53)  
  >34 7558 (12) 276 (160–547)   2164 (29) 1162 (15) 4232 (56)  
Pre- <18.5 2004 (3) 294 (160–554)   439 (22) 344 (17) 1221 (61)  
pregnancy 18.5-24.9 43198 (66) 278 (157–549) <0.0001 10611 (25) 8388 (19) 24199 (56) <0.0001
BMI in 25-30 13448 (21) 248 (148–533)   2999 (22) 2483 (18) 7966 (59)  
kg/m2 ≥30 5341 (8) 229 (141–515)   1146 (21) 822 (15) 3373 (63)  
  missing 1677 (3) 226 (144–491)   276 (16) 271 (16) 1130 (67)  
  0 33501 (51) 320 (165–566)   8753 (26) 6031 (18) 18717 (56)  
  1 20743 (32) 233 (146–526) <0.0001 4581 (22) 4466 (22) 11696 (56) <0.0001
Parity 2 9199 (14) 211 (144–480)   1752 (19) 1525 (17) 5922 (64)  
  3+ 2140 (3) 200 (140–388)   370 (17) 272 (13) 1498 (70)  
  missing 85 (0,1) 183 (121–401)   15 (18) 14 (16) 56 (66)  
Marital yes 63134 (96) 268 (154–544) <0.0001 15184 (24) 12101 (19) 35849 (57) <0.0001
status no 2534 (4) 232 (147–493)   287 (11) 207 (8) 2040 (81)  
Maternal <13 20618 (31) 214 (138–483)   3237 (16) 2774 (13) 14607 (71)  
education 13 - 16 27249 (41) 291 (157–553) <0.0001 6841 (25) 5601 (21) 14807 (54) <0.0001
in >16 16415 (25) 331 (171–569)   5096 (31) 3718 (23) 7601 (46)  
years missing 1386 (2) 243 (144–528)   297 (21) 215 (16) 874 (63)  
History of no 63433 (97) 267 (154–543) <0.0001 14980 (24) 11879 (19) 36574 (58) 0.18
preterm yes 2155 (3) 237 (151–521)   472 (22) 411 (19) 1272 (59)  
delivery missing 80 (0,1) 252 (144–554)   19 (24) 18 (23) 43 (54)  
History of no 53123 (81) 269 (154–544) <0.0001 11655 (22) 10112 (19) 31356 (59) <0.0001
abortion yes 12545 (19) 251 (150–540)   3816 (30) 2196 (18) 6533 (52)  
  never 59678 (91) 277 (156–548)   14752 (25) 11691 (20) 33235 (56)  
Smoking occasionally 1879 (3) 218 (141–453) <0.0001 255 (14) 231 (12) 1393 (74) <0.0001
habits daily 3733 (6) 190 (128–390)   399 (11) 319 (9) 3015 (81)  
  missing 378 (1) 221 (140–451)   65 (17) 67 (18) 246 (65)  
Alcohol no alcohol 55368 (84) 289 (159–551)   13360 (24) 10672 (19) 31336 (57)  
consumption <0.5 6565 (10) 245 (150–528) <0.0001 1403 (21) 1162 (18) 4000 (61) <0.0001
in units/week ≥0.5 3735 (6) 149 (117–209)   708 (19) 474 (13) 2553 (68)  
Partners with 0 19439 (30) 225 (143–507) <0.0001 3246 (17) 2853 (15) 13340 (69)  
income of 1 26938 (41) 265 (154–542) 6287 (23) 5253 (20) 15398 (57) <0.0001
>300,000 2 17472 (27) 337 (169–572) 5687 (33) 3939 (23) 7846 (45)  
NOK/year missing 1819 (3) 227 (147–511)   251 (14) 263 (14) 1305 (72)  
Baby's male 33445 (51) 262 (152–541) 0.003 7875 (24) 6198 (19) 19372 (58) 0.3
sex female 32223 (49) 270 (155–545)   7596 (24) 6110 (19) 18517 (57)  
Tertiles of 1 21890 (33) 179 (115–503)   5251 (24) 4031 (18) 12608 (58)  
energy intake 2 21890 (33) 263 (155–548) <0.0001 5397 (25) 4307 (20) 12186 (56) <0.0001
in MJ 3 21888 (33) 325 (203–591)   4823 (22) 3970 (18) 13095 (60)  
  1. Amount of total daily folate intake (FFQ data) and initiation of folic acid supplementation (Q1 data) according to maternal characteristics, from 65,668 participants in the Norwegian Mother and Child Cohort Study (2002 – 2009).
  2. 1 p-value, estimated with Kruskal-Wallis test.
  3. 2 p-value, estimated with Pearson's chi-squared test.