The link between smoking and miscarriages is controversial and not yet well understood, but numerous studies have found statistical links between exposure to cigarette smoke and risk of pregnancy loss. Avoiding cigarette smoke is probably one of the biggest ways that women can reduce miscarriage and stillbirth risk (although, again, nothing will eliminate risk entirely, and even women with no miscarriage risk factors can have pregnancy losses).
Occasional, light drinking before conception probably does not affect risk of miscarriage, and recent research has found that having drunk heavily once or twice before finding out about a pregnancy is not likely to cause miscarriage.
However, regular intake of even moderate amounts of alcohol – especially while pregnant – is correlated with a higher risk of miscarriage.
Beside alcohol, using other drugs can be associated with increased risk of both miscarriage and of stillbirth. Marijuana may reduce oxygen supply to the baby, increasing risk of low birthweight, preterm delivery, and stillbirth. Cocaine increases miscarriage risk and risk of placental abruption, as does use of methamphetamines.
Certain Prescription Medications
Although they are used for legitimate health concerns, several prescription drugs are associated with increased risk of miscarriage and stillbirth. One common example is ACE inhibitors, a type of blood pressure medication. Drugs with FDA pregnancy safety rankings in Category D or Category X may be associated with pregnancy loss risk.
The link between caffeine and miscarriage is controversial; some studies have found a link with moderate to heavy caffeine intake. Other studies dispute this link, and some theorize the link between caffeine and miscarriage might instead by explained by a tendency toward more coffee intake by women already destined to miscarry (they tend to experience less nausea and morning sickness.)
Until researchers better understand the connection between caffeine and miscarriage, it seems prudent to avoid heavy exposure to caffeine while pregnant just to be on the safe side.
With adequate prenatal care, women with chronic health conditions have excellent chances to have a normal pregnancy. But some health conditions, such as diabetes and systemic lupus erythematosus, may mean increased miscarriage or stillbirth risk if a woman conceives when the conditions are not under control.
Certain chemicals, such as pesticides and other petrochemicals, are known to increase risk of miscarriage. Women working around chemicals, and women whose partners work around chemicals, may have increased pregnancy loss risks.
American Pregnancy Association, “Using Illegal Drugs During Pregnancy.” May 2007. Accessed 31 Dec 2007.
American Pregnancy Association, "What's the Real Scoop on Caffeine During Pregnancy." Aug 2007. Accessed 31 Dec 2007.
Figa-Talamanca, Irene. "Occupational risk factors and reproductive health of women." Occupational Medicine 2006. Accessed 31 Dec 2007.
Rasch, V, "Cigarette, alcohol, and caffeine consumption: risk factors for spontaneous abortion." Acta Obstetrics and Gynecology Scandinavia Feb 2003. Accessed 31 Dec 2007.