We’ve already covered the issue of drinking alcohol while pregnant. Now it’s time for smoking.

When a pregnant mother smokes cigarettes, nicotine and carbon monoxide pass across the placental barrier. This disrupts the normal transfer of oxygen and nutrients to the developing fetus, harming its development.

Smoking in pregnancy

It’s been estimated that nearly 1 in 10 American women smoke cigarettes while pregnant (1). This is an alarming statistic considering that studies have repeatedly shown maternal smoking to be associated with adverse birth outcomes such as low birth weight (LBW), miscarriage, and infant mortality.

LBW infants are the result of a preterm birth, intrauterine growth retardation, or both. Nearly twice as many infants born to smokers have a low birth weight when compared to infants of nonsmokers (1), putting them at risk for cerebral palsy, mental retardation, and learning problems. Smoking during pregnancy has also been linked to respiratory disease and sudden infant death syndrome (2).

The effect of maternal smoking on the fetus depends on when it occurs. As we’d reported with drinking, smoking does the most harm during the early stages of pregnancy and the least during the later stages of pregnancy.

What about marijuana?

Studies of marijuana use during pregnancy provide some inconsistent results. Some studies link maternal marijuana use to growth retardation, preterm birth, decreased head circumference, and learning disabilities (3). One study concluded that marijuana has no adverse effects on children up to the age of 3, but after age 3, children who are exposed to cannabis in-utero are more likely to demonstrate attention deficit, hyperactivity, delinquent behavior, and decreased reasoning ability (4). Other studies find absolutely no association between marijuana and adverse birth outcomes.

The truth is, we don’t really know what marijuana use during pregnancy does to an infant, partially because researchers face two unique problems when studying maternal marijuana use:

1) Social stigma against drug use during pregnancy is likely causing women nationwide to under report their marijuana use.

2) Marijuana users are more likely to be using alcohol, cigarettes, and other illicit drugs. It is well known that poly-drug use during pregnancy greatly increases the chance of adverse birth outcomes (5).

So, smoking cigarettes and weed apparently does not consistently cause the same harm that drinking causes. However, the harm brought about by smoking seems to depend less on the amount smoked and more on the combination of substances used and its timing.

Keep on the lookout for more posts on drug use during pregnancy!

Citations:

1. Martin, J. A., Hamilton, B. E., Sutton, P. D., et al., (2003). Births: Final data for 2005, National Vital Statistics Reports, 56(6)

2. Difranza, J. R., Aligne, C.A., & Weitzman, M., (2004). Prenatal and postnatal environmental tobacco smoke exposure and children’s health, Pediatrics, 113, pg 1007-1015

3. Hatch, E. E., & Bracken, M.B., (1986) Effect of marijuana use in pregnancy on fetal growth, American Journal of Epidemiology, 124, pg 986-993.

4. Huizink, A. C., Mulder, E. J. H., (2006). Maternal smoking, drinking, or cannabis use during pregnancy and neurobehavioral and cognitive functioning in human offspring, Neuroscience and Biobehavioral Reviews, 30, pg 24-41

5. Hall W., and Solowij, N., (1998). Adverse effects of cannabis. The Lancet, 352, pg 1611-1616