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Table 1 Number and distribution of two cohorts of singleton births in Sweden, with mean and standard deviation (SD) of birthweight, birth length, and Apgar score by infant sex and gestational age, before and after the implementation of ultrasound for pregnancy dating

From: Effects of ultrasound pregnancy dating on neonatal morbidity in late preterm and early term male infants: a register-based cohort study

  1973–1978 1995–2010
Male Female Male Female
  Gestational age N % N % N % N %
35–40 weeks 187,163 100.0 170,375 100.0 479,118 100.0 477,946 100.0
35–36 weeks 8,737 4.7 6,733 4.0 20,527 4.3 18,095 3.8
37–38 weeks 41,434 22.1 33,746 19.8 122,074 25.5 121,500 25.4
39–40 weeks 136,992 73.2 129,896 76.2 336,517 70.2 338,351 70.8
Gestational age Infant characteristics Mean SD Mean SD Mean SD Mean SD
35–36 weeks Birthweight (g) 2,850 499 2,749 503 2,846 452 2,778 461
Birth length (cm) 47.9 2.5 47.3 2.4 47.6 2.2 47.0 2.2
Apgar score 9.2 1.3 9.2 1.3 9.5 1.0 9.6 1.0
37–38 weeks Birthweight (g) 3,284 472 3,159 465 3,349 460 3,254 450
Birth length (cm) 49.7 2.1 48.9 2.1 49.6 2.0 48.9 2.0
Apgar score 9.5 0.9 9.5 0.9 9.8 0.7 9.8 0.6
39–40 weeks Birthweight (g) 3,591 463 3,451 446 3,665 451 3,544 437
Birth length (cm) 51.0 2.0 50.1 2.0 51.0 1.9 50.2 1.8
Apgar score 9.6 0.8 9.6 0.7 9.8 0.7 9.8 0.6