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Table 1 Comparison of demographic and clinical characteristics of participants across maternal age groups

From: Adverse maternal and neonatal outcomes among singleton pregnancies in women of very advanced maternal age: a retrospective cohort study

  20–34 years 35–42 years ≥ 43 years Overall P
n % n % n % n
N 298,844 77.4 83,913 21.7 3266 0.8 386,023  
Maternal age, year (mean ± SD) 28.7 ± 3.7   37.2 ± 2.0   44.2 ± 1.9    < 0.001
Gravidity (median, IQR) 2 (2)   2 (2)   3 (3)    < 0.001
Parity (Median, IQR) 1 (1)   1 (2)   1 (2)    < 0.001
 0 137,021 45.9 22,231 26.5 910 27.9 160,162 < 0.001
 1 103,802 34.7 32,606 38.9 958 29.3 137,366  
 ≥2 53,739 18.0 27,619 32.9 1342 41.1 82,700  
 Missing 4282 1.4 1457 1.7 56 1.7 5795  
Neighbourhood income quintile
 1st (Lowest) 69,635 23.3 16,583 19.8 753 23.1 86,971 < 0.001
 2nd 55,635 18.6 13,656 16.3 523 16.0 69,814  
 3rd 53,391 17.9 13,787 16.4 536 16.4 67,714  
 4th 54,983 18.4 16,644 19.8 576 17.6 72,203  
 5th (Highest) 52,827 17.7 20,171 24.0 758 23.2 73,756  
 Missing 12,373 4.1 3072 3.7 120 3.7 15,565  
Neighbourhood education quintile a
 1st (Lowest) 56,392 18.9 9173 10.9 381 11.7 65,946 < 0.001
 2nd 62,349 20.9 13,141 15.7 510 15.6 76,000  
 3rd 61,921 20.7 16,257 19.4 574 17.6 78,752
 4th 61,929 20.7 21,041 25.1 767 23.5 83,737
 5th (Highest) 46,246 15.5 21,776 26.0 935 28.6 68,957
 Missing 10,007 3.3 2525 3.0 99 3.0 12,631
BMI (kg/m2) (mean ± SD) 25.3 ± 6.2   25.9 ± 6.1   26.4 ± 6.2    < 0.001
 Underweight (<18.5) 15,876 5.3 2634 3.1 64 2.0 18,574 < 0.001
 Normal weight (18.5–24.9) 134,814 45.1 35,362 42.1 1235 37.8 171,411  
 Overweight (25–29.9) 62,058 20.8 19,415 23.1 780 23.9 82,253  
 Obese (≥ 30) 46,129 15.4 14,087 16.8 580 17.8 60,796  
 Missing 39,967 13.4 12,415 14.8 607 18.6 52,989  
ART type
 IVF/ IVF + ICSI 2530 0.8 2890 3.4 575 17.6 5995 < 0.001
 IUI 3561 1.2 2026 2.4 82 2.5 5669
 Other 87 0.0 72 0.1 < 6 S 160
 None 292,666 97.9 78,925 94.1 2608 79.9 374,199
Previous cesarean section (yes) 35,687 11.9 18,038 21.5 732 22.4 54,457 < 0.001
Maternal health problems (yes) 30,889 10.3 11,607 13.8 562 17.2 43,058 < 0.001
 Pre-existing hypertension 2025 0.7 1369 1.6 117 3.6 3511 < 0.001
 Pre-gestational diabetes mellitus 2427 0.8 1216 1.4 76 2.3 3719 < 0.001
 Maternal heart disease 3407 1.1 1125 1.3 46 1.4 4578 < 0.001
 Maternal pulmonary diseases 12,188 4.1 3038 3.6 127 3.9 15,353 < 0.001
 Maternal endocrine disorders 12,569 4.2 5712 6.8 268 8.2 18,549 < 0.001
 Thrombophilia 198 0.1 69 0.1 7 0.2 274 0.003
Drug/alcohol/tobacco use (yes) 38,228 12.8 5897 7.0 209 6.4 44,334 < 0.001
 Drug use (any drug) 6051 2.0 680 0.8 21 0.6 6752 < 0.001
 Alcohol use b 5489 1.8 1499 1.8 65 2.0 7053 0.26
 Maternal smoking c 32,974 11.0 4427 5.3 157 4.8 37,558 < 0.001
Infant gender
 Male 153,326 51.3 42,894 51.1 1643 50.3 197,863 0.62
 Female 145,323 48.6 40,968 48.8 1622 49.7 187,913
 Undetermined or missing 195 0.1 51 0.1 < 6 S 247
  1. ART assisted reproductive technology, BMI body mass index, ICSI intracytoplasmic sperm injection, IQR interquartile range, IUI intra-uterine insemination, IVF in vitro fertilization, S suppression due to cell < 6, SD standard deviation
  2. aPercentage of university degrees among population between 25 and 64 years old at dissemination areas level
  3. bAlcoholic drink during pregnancy
  4. cSmoking at any time during pregnancy