When a mother smokes during pregnancy, she places her baby and herself at risk for dangerous consequences. Smoking causes increased chances for miscarriage, growth restriction, preterm birth, birth defects, and health problems after birth. Quitting smoking by the end of the first trimester of pregnancy greatly reduces the risk for these problems.
Miscarriage and Stillbirth
Smoking during pregnancy increases the chance for both miscarriage, or death of the fetus before about 20 weeks gestation, and stillbirth, or death after about 20 weeks gestation. The reasons for this are not entirely known, but the over 4,000 chemicals and toxins present in cigarette smoke, including arsenic, carbon monoxide and formaldehyde, most likely play a role. These chemicals enter the mother's bloodstream when she smokes. Her blood, which is supposed to deliver only oxygen and nutrients to the baby, now delivers dangerous chemicals as well that can prove lethal.
Growth Restriction
Smoking not only infuses the mother's bloodstream with dangerous chemicals, but also constricts blood vessels that supply the placenta. Constricted blood vessels cannot carry sufficient blood to the baby, impairing the baby's growth. A doctor can diagnose growth restriction by taking measurements of certain body parts with ultrasound and comparing those measurements to what is expected at that gestational age. Growth restriction leads to low birth weight and small body size, which increases the chance for health problems in the newborn.
Preterm Delivery
Women who smoke also place their pregnancies at increased risk of being delivered preterm, or before 37 weeks gestation. Smoking is associated with premature rupture of membranes (PROM), which is when the bag of water that surrounds the baby breaks before labor begins. PROM can cause several severe complications that can jeopardize the health and life of the baby and mother. One of these complications is premature birth. Premature babies can suffer from neurological damage, bleeding inside the brain and heart problems, among other conditions.
Birth Defects
The chance for birth defects such as heart and limb abnormalities and facial clefts is believed to be increased for babies exposed prenatally to smoke. According to a study published in the journal Epidemiology in 2010, mothers exposed to even second-hand smoke have a higher chance for babies with cleft lip with or without cleft palate. The risk for these defects is highest in the first trimester of pregnancy, when the fetal organs are forming.
Health Problems After Birth
Smoke-exposed babies that survive the pregnancy can develop many problems after birth. Small, underweight babies and those born premature have increased chances for infection, jaundice and breathing problems in the newborn period. Some health problems extend beyond the first few days or weeks and can include asthma and learning disabilities. The rate of sudden infant death syndrome (SIDS) during a baby's first year of life is also higher among babies whose mothers smoked during and/or after pregnancy.
References
- British Medical Journal; "Smoking Is Causing Impotence, Miscarriages, and Infertility"; Z Kmietowicz; Feb. 2004
- Stop Smoking Steps: Added Toxins in Cigarettes
- Pediatrics; "Short-term Health and Economic Benefits of Smoking Cessation: Low Birth Weight"; JM Lightwood et al; Dec. 1999
- Epidemiology; "Maternal Passive Smoking and Risk of Cleft Lip Cleft Palate"; Z Li et al; Mar 2010
