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Table 4 Descriptive statistics of the raw scores on triplet BW and GA, and percentage of smoking and alcohol consumption during pregnancy, as a function of zygosity

From: Birth weight in a large series of triplets

  MZ DZ TZ
N trios 37 102 271
N boys/girls 41/70 145/161 387/426
GA mean (sd) 33.3 (2.15) 33.6 (2.89) 33.7 (2.52)
N mothers consuming alcohol 3 (8%) 19 (19%) 36 (13%)
N mothers smoking 6 (16%) 19 (19%) 49 (18%)
  MZ MZ* DZ** TZ
Mean BW first born (grams) 1852 1952 2017 1954
Mean BW second born (grams) 1759 1887 1941 1933
Mean BW third born (grams) 1789 1831 2107 1829
Variance triplet BW 157 230 262 215
Pair-wise covariance triplet BW 110 162 156 144
Pair-wise correlation triplet BW 0.70 0.70 0.64 0.67
SGA first born (% SE ss/US ss/US ts) 19/42/3 22/38/5 27/37/7 25/44/7
SGA sec. born (% SE ss/US ss/US ts ) 41/57/14 41/24/5 14/59/13 25/41/9
SGA third born (% SE ss/US ss/US ts) 32/51/16 35/39/8 18/33/11 18/52/15
  1. *MZ triplets from DZ trios; ** DZ triplets from DZ trios; GA = gestational age; BW = birth weight; SGA = small for gestational age; US ss = United States' singleton standard; US ts = US triplet standard; SE ss = Swedisch singleton standard; MZ = monozygotic; DZ = dizygotic; TZ = trizygotic.