Table 1.

Distribution of age across cases and controls.

Age range (y)	Cases (n = 202)	Controls (n = 202)
15–19	0	0
20–24	12	12
25–29	59	58
30–34	78	79
35–39	35	36
40–44	17	16
45–49	1	1

Median age of all 404 obstetric patients: 31 y, interquartile range (IQR): 28 to 35 y, range 20 to 46 y; mean 31.7 y, standard deviation (SD) 5.04. Of the 202 pairs of maternal ages, the median difference between cases and controls was 0 years (IQR −2 to 1 years, range −4 to 4 years).