Table 2.

Difference in standardized mean examination scores according to gestational weeks from the Danish cohort study

	Standardized mean grade difference (regression coefficient (95% CI)) a
	Mathematics 1	Mathematics 2	Danish 1	Danish 2	Danish 3
	Solving abilities	Mathematical skills	Oral	Reading comprehension	Spelling
Preterm birth
≥ 37	REF	REF	REF	REF	REF
< 37	− 0.054 (− 0.066 to − 0.042)	− 0.077 (− 0.089 to − 0.065)	− 0.020 (− 0.032 to − 0.008)	− 0.066 (− 0.078 to − 0.054)	− 0.036 (− 0.048 to − 0.024)
Gestational weeks
Difference b	0.009 (0.007 to 0.011)	0.013 (0.011 to 0.014)	0.004 (0.002 to 0.005)	0.010 (0.008 to 0.011)	0.006 (0.004 to 0.007)
≥ 40 weeks	REF	REF	REF	REF	REF
≤ 33	− 0.141 (− 0.166 to − 0.117)	− 0.179 (− 0.203 to − 0.155)	− 0.037 (− 0.061 to − 0.012)	− 0.118 (− 0.142 to − 0.094)	− 0.051 (− 0.074 to − 0.027)
34 ~ 35	− 0.039 (− 0.060 to − 0.019)	− 0.067 (− 0.088 to − 0.047)	− 0.019 (− 0.040 to 0.001)	− 0.070 (− 0.090 to − 0.050)	− 0.037 (− 0.058 to − 0.017)
36	− 0.025 (− 0.044 to − 0.007)	− 0.040 (− 0.059 to − 0.021)	− 0.015 (− 0.034 to 0.003)	− 0.043 (− 0.062 to − 0.025)	− 0.033 (− 0.052 to − 0.015)
37 ~ 39	− 0.012 (− 0.017 to − 0.006)	− 0.017 (− 0.022 to − 0.012)	− 0.005 (− 0.011 to − 0.000)	− 0.011 (− 0.016 to − 0.006)	− 0.008 (− 0.013 to − 0.003)
p for trend	< 0.001	< 0.001	0.003	< 0.001	< 0.001

^aAdjusted for sex, calendar year, parity, maternal age, paternal age, maternal education, maternal origin, maternal cohabitation at birth, maternal history of psychiatric disorders before the childbirth, and paternal history of mental disorders before the childbirth; CI, confidence interval; REF, referenced gestational week

^bIn the results of this regression model, the effect estimates represent the difference in standard deviation per 1-week longer gestational duration

^cThe effect estimates represent their differences when compared to ≥ 40-week gestation