In New Zealand one in three preschool children (<5 years of age) are overweight or obese, escalating to 54% in Pasifika children. Despite alarming rates of preschool obesity, remarkably in recent years we have shown this rate has progressively declined across the country for 10 years, which has not been reported in any other country. This has occurred across all ethnicities, socioeconomic classes and regions in NZ. This reduction in preschool obesity began between 2000 and 2010. The key question is what has occurred in NZ at a national level that led to this change. From the early 2000’s NZ launched a strong anti-smoking campaign that included progressive tobacco taxation and from 2005 graphic hard-hitting anti-smoking TV advertisements.
New Zealand’s anti-smoking campaign is associated with a reduction in smoking in pregnancy which is associated with a reduction in preschool obesity.
The New Zealand Government’s 22 national datasets are now all integrated (the Integrated Data Infrastructure). Data from four of these datasets were linked and analysed; national smoking records, the maternity health records, birth records and the Before School Health Check (4-5 year old children). Tobacco smoking data in pregnancy and lactation, birth weight, gestation, ethnicity and birth weight, together with BMI at 4-5 years of age were collected. BMI expressed as BMI SDS. Birth and childhood BMIs were adjusted for maternal BMI and childhood BMI for birth weight.
Data was collected on 312,000 mother and child pairs nationwide. Smoking in pregnancy and lactation is still common in NZ. In Māori women 37% and in Pasifika 18% smoked in pregnancy compared to 9% in Europeans. In addition, smoking is more common in less affluent women. Importantly, there has been a dramatic reduction in smoking in NZ women of childbearing age between 2006-2018, most notably between 2006-2013 when the campaign was most active. Between 2006-2018 there was a major reduction in the percentage of regular smokers in women aged 15-39 years, from 53.5% in 2006 down to 14.8% in 2018. This reduction occurred across all ethnicities, most markedly in Māori and Pasifika women.
Smoking during pregnancy was associated with an increased risk of small for gestational age (birth weight <-2 SDS) newborns with risks for light (ORadjusted 3.2) medium (ORadjusted 4.2) and heavy smoking (ORadjusted 4.7). Evaluation of women who smoked in pregnancy only and postnatally only showed independent effects of SGA with ORadjusted of 2.3 and 2.6 respectively.
Smoking during pregnancy was associated with an increased risk of childhood obesity at 4-5 years of age with risks for light (ORadjusted 1.38) medium (ORadjusted 1.49) and heavy smoking (ORadjusted 1.6). Evaluation of women who smoked in pregnancy only and postnatally only showed independent effects of childhood obesity with ORadjusted of 1.35 and 1.44 respectively.
There has been reduction in smoking during pregnancy and lactation, both associated with a reduction in preschool overweight/obesity in NZ children. We speculate that the reduction in smoking in pregnancy has contributed to the fall in preschool obesity in NZ.