Birth Weight Ratio as an Alternative to Birth Weight Percentile to Express Infant Weight in Research and Clinical Practice: A Nationwide Cohort Study

Table 1

Characteristics of the 1,299,244 pregnancies in the Netherlands, 1999–2007.

	Total
	(n = 1,299,244)
Maternal characteristics
Maternal age, mean, (SD)	30.7 (4.58)
Nulliparous, %	47.5
Low socioeconomic status, %	18.9
Boys	51.3
Pregnancy and delivery
Induction of labor, %	35.3
Cesarean section	14.3
Elective cesarean section %	6.2
Emergency cesarean section %	11.3
Vaginal instrumental delivery	12.4
Neonatal characteristics
Gestational age at delivery (weeks), median (IQR)	39,2 (1.86)
Extremely premature (GA < 29^+0 weeks), (%)	4,048 (0.3)
Very premature (GA < 33^+0 weeks), (%)	13,885 (1.1)
Mild premature (GA < 37^+0 weeks), (%)	75,429 (5.81)

SD, standard deviation.