Table 3.

General and trimester-specific univariate associations of potential confounders and gestational duration (weeks)

	Effect size (βa)	95% CI	P valueb
General
Male sex of child	0.16	0.10, 0.23	<0.001
History of LBW	−1.08	−1.23, −0.92	<0.001
History of PTB	−1.17	−1.31, −1.03	<0.001
History of spontaneous abortion	0.02	−0.06, 0.10	NS
History of hypertension	−0.23	−0.32, −0.13	<0.001
Hospitalisation during pregnancy	−0.32	−0.51, −0.14	<0.001
Parity	0.01	−0.04, 0.06	NS
Home ownership	−0.02	−0.05, 0.02	NS
Marital status (married)	−0.02	−0.05, 0.01	NS
Maternal educational level	−0.06	−0.12, −0.01	<0.001
Maternal social economic status	−0.01	−0.05, 0.00	NS
Paternal social economic status	−0.03	−0.03, 0.02	NS
Maternal BMI (pre-pregnancy)	2.94	2.88, 2.98	<0.001
Paternal weight	0.00	0.00. 0.01	NS
Paternal height	−0.01	−0.01, 0.00	NS
Maternal age at LMP	−0.25	−0.34, −0.15	NS
Maternal age at delivery	0.24	0.15, 0.33	0.031
Smoking before pregnancy	0.12	−0.03, 0.27	NS
Drug abuse	0.01	−0.17, 0.19	NS
1st trimester
Smoking	−0.02	−0.23, 0.20	NS
Alcohol use	−0.02	−0.09, 0.04	NS
2nd trimester
Smoking	0.07	0.31, 0.18	0.004
Alcohol use	−0.01	−0.06, 0.06	NS
Negative mood	−0.01	−0.01, 0.00	NS
Poor maternal health	−0.003	−0.02, 0.01	NS
In paid work	0.06	−0.02, 0.14	NS
Shift work	−0.12	−0.29, 0.05	NS
Night shifts	0.21	−0.02, 0.44	NS
3rd trimester
Smoking	−0.10	−0.33, 0.13	NS
Alcohol use	−0.92	−1.85, −0.01	0.031
Negative mood	0.01	−0.01, 0.01	NS
Poor maternal health	−0.83	−1.22, −0.44	<0.001
In paid work	−0.08	−0.15, −0.01	0.023
Shift work	0.06	−0.22, 0.34	NS
Night shifts	−0.06	−0.45, 0.34	NS

CI confidence interval

^aBeta (regression coefficient)

^bStatistically significant P < 0.05