Table 1

Baseline characteristics of women in the study by year of enrolment

CharacteristicsYears
2009
N (%)
6433 (100)
2010
N (%)
10 447 (100)
2011
N (%)
9626 (100)
2012
N (%)
9905 (100)
2013
N (%)
9496 (100)
2014
N (%)
9454 (100)
2015
N (%)
10 108 (100)
2016
N (%)
7281 (100)
Total
N (%)
72 750 (100)
Mother’s age (years)*
 <20131 (2)209 (2)181 (1.9)188 (1.9)190 (2)193 (2)209 (2.1)157 (2.2)1458 (2)
 20–296044 (94)9867 (94.4)9056 (94.1)9269 (93.6)8834 (93)8743 (92.5)9266 (91.7)6640 (91.2)67 719 (93.1)
 >29258 (4)371 (3.6)389 (4)448 (4.5)472 (5)518 (5.5)633 (6.3)484 (6.6)3573 (4.9)
Mother’s education (grades)*
 Primary or less (≤4)1476 (22.9)2281 (21.8)1846 (19.2)1927 (19.5)1882 (19.8)693 (7.3)633 (6.3)329 (4.5)11 067 (15.2)
 Secondary (5–10)3814 (59.3)6210 (59.4)5818 (60.4)5880 (59.4)5432 (57.2)4962 (52.5)5101 (50.5)3522 (48.4)40 739 (56)
 University (>10)1139 (17.7)1956 (18.7)1958 (20.3)2071 (20.9)2172 (22.9)3768 (39.9)4358 (43.1)3415 (46.9)20 837 (28.6)
Missing4 (0.1)0 (0)4 (0)27 (0.3)10 (0.1)31 (0.3)16 (0.2)15 (0.2)107 (0.1)
Parity*
 Nulliparous2905 (45.2)5118 (49)4706 (48.9)4817 (48.6)4384 (46.2)4530 (47.9)4967 (49.1)3598 (49.4)35 025 (48.1)
 1–23300 (51.3)5032 (48.2)4669 (48.5)4827 (48.7)4907 (51.7)4721 (49.9)4888 (48.4)3544 (48.7)35 888 (49.3)
 >2228 (3.5)297 (2.8)249 (2.6)261 (2.6)204 (2.1)197 (2.1)234 (2.3)137 (1.9)1807 (2.5)
 Missing0 (0)0 (0)2 (0)0 (0)1 (0)6 (0.1)19 (0.2)2 (0)30 (0)
Anaemia (g/dL)
 Moderate/severe (<10)2962 (46)5283 (50.6)4620 (48)4730 (47.8)4682 (49.3)4418 (46.7)5058 (50)3457 (47.5)35 210 (48.4)
 Mild (10<11)2743 (42.6)4341 (41.6)4033 (41.9)4337 (43.8)4006 (42.2)4152 (43.9)4041 (40)2948 (40.5)30 601 (42.1)
 Normal (≥11)728 (11.3)823 (7.9)973 (10.1)838 (8.5)808 (8.5)884 (9.4)1009 (10)876 (12)6939 (9.5)
BMI (kg/m2)*
 Underweight (<18.5)1784 (27.7)3537 (33.9)3391 (35.2)3450 (34.8)3411 (35.9)3424 (36.2)3786 (37.5)2788 (38.3)25 571 (35.1)
 Normal (18.5–24.9)4426 (68.8)6558 (62.8)5931 (61.6)6061 (61.2)5699 (60)5619 (59.4)5789 (57.3)4095 (56.2)44 178 (60.7)
 Overweight or obese (≥25)223 (3.5)352 (3.4)304 (3.2)394 (4)386 (4.1)411 (4.3)533 (5.3)398 (5.5)3001 (4.1)
Anaemia (g/dL)–BMI (kg/m2) factors
 Anaemic (<11)–normal (≥18.5)4070 (63.3)6256 (59.9)5522 (57.4)5823 (58.8)5463 (57.5)5384 (56.9)5569 (55.1)3857 (53)41 944 (57.7)
 Anaemic (<11)–underweight (<18.5)1635 (25.4)3368 (32.2)3131 (32.5)3244 (32.8)3225 (34)3186 (33.7)3530 (34.9)2548 (35)23 867 (32.8)
 Non-anaemic (≥11)–normal (≥18.5)579 (9)654 (6.3)713 (7.4)632 (6.4)622 (6.6)646 (6.8)753 (7.4)636 (8.7)5235 (7.2)
 Non-anaemic (≥11)–underweight (<18.5)149 (2.3)169 (1.6)260 (2.7)206 (2.1)186 (2)238 (2.5)256 (2.5)240 (3.3)1704 (2.3)
BMI (kg/m2) (mean/SD/IQR)20.1/2.6/3.419.7/2.6/3.219.6/2.6/3.419.7/2.7/3.519.7/2.8/3.619.7/2.9/3.619.7/3/3.719.7/3/3.719.7/2.8/3.6
Haemoglobin (g/dL) (mean/SD/IQR)9.8/0.9/19.7/0.9/19.7/0.8/1.19.8/0.8/19.9/0.8/0.89.9/0.8/0.89.9/0.8/19.9/0.9/19.8/0.8/1
  • *Highly significant (p<0.001) non-parametric trend over years of enrolment.

  • BMI, body mass index.