To dispel any uncertainty about the serious harm caused by smoking to babies and pregnant women, the first-ever comprehensive systematic review of all studies over the past 50 years has established clearly that maternal smoking causes a range of serious birth defects including heart defects, missing/deformed limbs, clubfoot, gastrointestinal disorders, and facial disorders (for example, of the eyes and cleft lip/palate).
Smoking during pregnancy is also a risk factor for premature birth, says Dr. Michael Katz, senior Vice President for Research and Global Programs of the March of Dimes. He says the March of Dimes urges all women planning a pregnancy or who are pregnant to quit smoking now to reduce their chance of having a baby born prematurely or with a serious birth defect. Babies who survive being born prematurely and at low birthweight are at risk of other serious health problems, Dr. Katz notes, including lifelong disabilities such as cerebral palsy, intellectual disabilities and learning problems. Smoking also can make it harder to get pregnant, and increases the risk of stillbirth.
About 20 percent of women in the United States reported smoking in 2009. Around the world, about 250 million women use tobacco every day and this number is increasing rapidly, according to data presented at the 2009 14th World Conference on Tobacco or Health in Mumbai.
The new study, "Maternal smoking in pregnancy and birth defects: a systematic review based on 173,687 malformed cases and 11.7 million controls," by a team led by Allan Hackshaw, Cancer Research UK & UCL Cancer Trials Centre, University College London, will be published online today in Human Reproduction Update from the European Society of Human Reproduction and Embryology.
When women smoke during pregnancy, the unborn baby is exposed to dangerous chemicals like nicotine, carbon monoxide and tar, Dr. Katz says. These chemicals can deprive the baby of oxygen needed for healthy growth and development.
During pregnancy, smoking can cause problems for a woman's own health, including:
placental abruption, in which the placenta peels away, partially or almost completely, from the uterine wall before delivery;
placenta previa, a low-lying placenta that covers part or all of the opening of the uterus.
Smoking is also known to cause cancer, heart disease, stroke, gum disease and eye diseases that can lead to blindness.