Table 3.

Role of maternal cigarette smoking and alcohol consumption during pregnancy on the placenta-to-birth weight ratio, placental weight and birth weight

Factors	Placenta-to-birth weight ratio (g/kg) β (95% CI)^c	Placental weight (g) β (95% CI)^c	Birth weight (g) β (95% CI)^c
1^st trimester
Smoking
Nil	Ref	Ref	Ref
1–10 cigarettes/day	4.84 (2.55, 7.12)^**	−15.19 (−24.84, −5.54)^*	−180.83 (−214.32, −147.34)^**
11–20 cigarettes/day	7.40 (4.99, 9.80)^**	−16.40 (−26.58, −6.23)^*	−226.14 (−261.37, −190.92)^**
21+ cigarettes/day	8.64 (5.34, 11.94)^**	−13.09 (−27.05, 0.87)	−231.66 (−280.05, −183.28)^**
Any alcohol consumption (yes, no)	−2.60 (−4.49, −0.70)^*	−5.77 (−13.80, 2.26)	8.19 (−19.62, 36.01)
2^nd trimester
Smoking
Nil	Ref	Ref	Ref
1–10 cigarettes/day	7.41 (5.09, 9.74)^**	−9.18 (−19.04, 0.67)	−196.76 (−230.90, −162.63)^**
11–20 cigarettes/day	7.24 (4.81, 9.67)^**	−18.83 (−29.15, −8.50)^**	−233.04 (−268.59, −197.50)^**
21+ cigarettes/day	10.59 (7.18, 14.01)^**	−5.37 (−19.88, 9.13)	−233.33 (−283.41, −183.26)^**
Any alcohol consumption (yes, no)	−2.13 (−4.08, −0.19)^*	−4.39 (−12.61, 3.83)	13.00 (−15.46, 41.46)
3^rd trimester
Smoking
Nil	Ref	Ref	Ref
1–10 cigarettes/day	7.73 (5.39, 10.06)^**	−11.26 (−21.17, −1.35)^*	−211.65 (−245.92, −177.38)^**
11–20 cigarettes/day	7.93 (5.46, 10.40)^**	−14.21 (−24.73, −3.68)^*	−222.23 (−258.42, −186.03)^**
21+ cigarettes/day	9.81 (6.54, 13.07)^**	−5.14 (−19.00, 8.72)	−222.55 (−270.38, −174.72)^**
Any alcohol consumption (yes, no)	−0.56 (−1.21, 0.09)	−1.77 (−4.52, 0.97)	0.31 (−9.18, 9.81)

β-coefficient and 95% confidence interval for linear regression model adjusted for components of perinatal score except for birth weight (maternal age, neonatal gender, season of birth, duration of second stage labor and intention to breast feed), maternal education, infant parity, maternal pre-pregnancy BMI, total pregnancy weight change, any prenatal cigarette smoking (except when smoking was the main exposure), any prenatal alcohol consumption (except when alcohol consumption was the main exposure), and gestational age.

P<0.05,

^**

P<0.001