A new study by Stellenbosch University has revealed that women who smoke and drink during pregnancy are likely to give birth to stillbirth and Sudden Infant Death Syndrome (SIDS) also known as cot death.
The study, which was carried out among 12,000 women in South Africa and the US over an eight-year period, found the risk of cot death was 12-fold among smokers and those who drink alcohol.
In cases where the women drank but did not smoke, the risk for SIDS increased by 4 times. Among smokers, the risk of cot death was 5 times higher compared to non-smokers.
“This is the first study to show that combining these risk factors strengthens the negative effects on stillbirths and SIDS,” says Professor Hein Odendaal of the Department of Obstetrics and Gynaecology at Stellenbosch University.
“What’s particularly alarming is that these behaviours were quite common among study participants. More than half used alcohol (52.3%) sometime during pregnancy, and 17% continued drinking throughout the entire pregnancy. Almost half of them smoked (49%) sometime during pregnancy, and a third (33%) continued smoking for the duration of the pregnancy,” says Odendaal.
Between 2007 and 2015, this international study followed the drinking and smoking behaviour of nearly 12,000 South African and American women and collated the results with their pregnancy outcomes.
The researchers found that women who both drank alcohol and smoked during pregnancy had an almost three times higher risk (2.83 relative risk) of stillbirth compared to women who completely abstained from these behaviours.
Smoking alone had a relative risk of 1.6 for stillbirth, while drinking alone had a relative risk of 2.2. This risk increased when these behaviors continued beyond the first trimester of pregnancy (12 weeks gestation).
“There has never been such a large prospective study looking at the use of alcohol and tobacco in pregnancy in such detail. The researchers found that drinking and smoking reduced blood flow in the uterine and umbilical arteries (two of the main vessels involved in foetal nutrition and growth) as early as 20-24 weeks of gestation. Again a compound effect was noticed,” says Odendaal.
“Even low levels of drinking and smoking affected blood flow in the umbilical artery. Higher levels of smoking and drinking aggravated these effects on blood flow.”
The study also found an association between smoking and placental insufficiency – a complication of pregnancy where the placenta is unable to deliver an adequate supply of nutrients and oxygen to the foetus and can’t fully support the developing baby.