Table 1

Pregnancy and delivery characteristics among all women with singleton births in Finland during 1991−2010 (n=1 164 953) according to smoking status groups

Characteristic
Mean| (SD) or %
Non-smoking,
n=958 177 (82.3%)
Quit smoking, 30 136 (2.6%)Smoking, n=145 710 (12.5%)No information on smoking, n=30 930 (2.7%)
Mean maternal age, years (SD)29.6 (5.2)27.0 (5.5)27.3 (5.9)29.3 (5.5)
Nulliparous women40.160.143.834.6
Multiparous women59.939.956.265.4
Mean gestational age, weeks (SD)39.8 (1.7)39.9 (1.8)39.7 (2.0)39.3 (2.7)
Male infant51.150.951.351.0
Mean birth weight, grams (SD)3575 (547)3531 (546)3383 (568)3469 (688)
Mean Apgar score at 5 min (SD)9.1 (1.0)9.0 (1.0)9.0 (1.0)8.9 (1.4)
Mode of delivery
 Vaginal spontaneous77.674.478.575.9
 Breech0.40.40.40.5
 Forceps0.10.20.10.1
 Vacuum assisted6.48.45.75.3
 Caesarean section15.416.615.418.2
Prior miscarriages20.216.121.319.4
Prior terminations7.717.820.59.8
Anaemia ≤6.2 mmol/L0.71.40.70.5
Chorionic villus biopsy1.11.00.80.6
Amniocentesis3.32.42.92.7
Placenta previa0.20.20.20.2
Placental abruption0.30.30.60.7
Induction15.517.815.513.1
In vitro fertilisation1.00.70.30.6
Gestational diabetes7.69.87.67.5
Maternal diabetes mellitus5.37.35.35.5
Preeclampsia2.01.11.32.1
Socioeconomic status
 Upper white-collar worker93.41.03.42.2
 Lower white-collar worker85.02.310.42.3
 Blue-collar worker71.93.621.92.5
 Other*83.12.412.02.4
 Missing78.73.213.54.6
Married or living with a partner96.489.987.694.9
Time periods
 1991–199581.71.614.22.5
 1996–200082.61.513.12.8
 2001–200582.52.712.22.6
 2006–201082.34.610.32.7
  • *The ‘other’ group included entrepreneurs, students, retired, unemployed, housewives and unclassifiable cases.