Smoking can have devastating consequences for a pregnancy. From miscarriage to growth restriction to birth defects, smoking during pregnancy increases the risk for many poor outcomes. The more a woman smokes, the higher the risks. Being aware of these risks may provide the motivation necessary for women to kick their cigarette habit before becoming pregnant or as early as possible in the pregnancy.
Miscarriage and Stillbirth
Smoking cigarettes during pregnancy increases the chance for miscarriage (death of the fetus at less than 20 weeks of pregnancy) and stillbirth (death after about 20 weeks). Cigarette smoke contains more than 4,000 chemicals and toxins, including carbon monoxide and formaldehyde. These chemicals reach the baby through the mother's bloodstream and can overwhelm a tiny embryo or fetus. In addition, smoking constricts the blood vessels that supply the placenta. A placenta with insufficient blood supply can't properly support the needs of a growing baby.
Growth Restriction and Low Birthweight
Constricted blood vessels supplying the placenta can also lead to growth restriction for the baby. The mother's blood carries the oxygen and nutrients needed for the baby to grow. Therefore, less blood flow to the placenta means slower growth for the baby. A doctor can assess prenatal growth restriction with ultrasound. Babies that are growth-restricted are usually born underweight and small for their gestational age. While a small baby may sound appealing to some mothers, size matters immensely to the baby's health. Small, underweight babies can develop breathing problems, infections and jaundice after birth and are at increased risk for sudden infant death syndrome (SIDS). The good news is that stopping smoking by the end of the first trimester of pregnancy largely erases these risks.
Premature Rupture of Membranes
Women who smoke during pregnancy have an increased chance for premature rupture of membranes (PROM), which is when the amniotic sac that surrounds the baby breaks before labor begins. PROM can lead to severe complications, including placental abruption (early detachment of the placenta from the wall of the uterus), chorioamnionitis (an infection of the membranes of the placenta), and premature birth. These complications jeopardize the life of the baby and the mother. Premature babies face the same risks as underweight babies, plus they can develop a host of long-term conditions such as neurological problems and learning disabilities.
Birth Defects
Although studies vary regarding whether smoking during pregnancy can cause birth defects, several studies have shown that certain birth defects, including anomalies of the heart and limbs, occur more often in babies whose mothers smoked. One study, published in the journal "Epidemiology" in 2010, found that even secondhand smoke exposure in the mother increased the risk for cleft lip with or without cleft palate in the baby. The baby's organs form primarily during the first trimester, so smoking early in the pregnancy causes the highest risk for birth defects.
References
- StopSmokingSteps.com: Smoking During Pregnancy
- "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 With or Without Cleft Palate; Z Li et al; March 2010
- March of Dimes: Smoking During Pregnancy
