Table 2.

Country of Study, period of study, sample size, controlled confounding variables, and influence of paternal age on incidence of NSCS as shown in the case-control studies included in the review.

Article	Country, Period of Study	Sample Size (NSCS/control)	Controlled Confounding Covariables	Maternal Age Stratification	Prevalence Ratio (OR (95% CI))	Influence of Young Maternal Age	Influence of Advanced Maternal Age	Paternal Age Stratification	Prevalence Ratio (OR (95% CI))	Influence of Young Paternal Age	Influence of Advanced Paternal Age
Boulet et al. 2008	USA, 1989–2003	216/N/A	None	15–19 20–34 35–44	0.29 (0.13, 0.66) 1 2.20 (1.63, 2.99)a	None	Positive	N/A	N/A	N/A	N/A
Gill et al. 2012	USA, 1997–2007	966/8169	Maternal race, education, BMI, periconceptional folic acid, gravidity, smoking, parental age difference	<20 20–24 25–29 30–34 35–39 40+	0.6 (0.4, 0.8)a 0.8 (0.6, 1.0) 1 1.2 (1.0, 1.4) 1.3 (1.1, 1.6) 1.6 (1.1, 2.4)a	Negative	Positive	N/A	N/A	N/A	N/A
Lee et al. 2012	Australia, 1982–2008	522/N/A	None	<20 20–29 30–39 40_ 40+	0.64 (0.33, 1.25) 1 1.26 (1.04, 1.53)a 1.92 (1.17, 3.15)a	None	Positive	N/A	N/A	N/A	N/A
Reefhuis et al. 2004	USA, 1980–1994	396/1050616	Parity, maternal race, infant sex, year of birth	14–19 20–24 25–29 30–34 35–40	N/A N/A 1 N/A 1.65 (1.18, 2.30)a	None	Positive	N/A	N/A	N/A	N/A
Singer et al. 1999	Australia, 1980–1994	170/522	None	<20 20–24 25–29 30–34 35+	0.54 (0.23, 1.26) 0.89 (0.56, 1.42) 1 1.13 (0.73, 1.76) 1.80 (0.96, 3.41)	None	None	<25 25–29 30–34 35–39 40+	1.02 (0.57, 1.82) 1.21 (0.76, 1.91) 1 1.50 (0.85, 2.66) 2.72 (1.40, 5.28)∗	None	Positive
Urhoj et al. 2015	Denmark, 1978–2004	997/1605885	Maternal age, year of birth, parental education, parental ethnicity	N/A	N/A	N/A	N/A	<25 25–29 30–34 35–39 40–44 45–49 50+	1.03 (0.78, 1.35) 1.02 (0.86, 1.21) 1 1.11 (0.92, 1.34) 1.06 (0.79, 1.43) 1.27 (0.80, 2.01) 1.36 (0.71, 2.59)∗	None	Positive

^aStatistically significant.