Smoking while pregnant harms your unborn baby, as each cigarrette contains more than 4,000 chemicals. Carbon monoxide, nicotine and other toxic chemicals will access the placenta and go directly into the baby’s blood stream – so the baby smokes with you. This will reduce its oxygen and nourishment and put it at risk of low birth weight, premature birth and other problems.
Second hand smoke can also affect your baby, increasing the risk of cot death and causing a low birth weight. Babies whose parents smoke also are more likely to be admitted to hospital for pneumonia or bronchitis.
The sooner you stop smoking the better, to give your baby a healthier start in life. Your midwife can arrange referral to your local Smoking Cessation coordinator or group (see also NHS Pregnancy Smoking Helpline).
Cannabis smoking can have similar effects on the lungs, and the safety of using cannabis during pregnancy has not been established. http://www.givingupsmoking.co.uk/