PAPER: heavy smoking early in pregnancy, smokers more than twice as likely as non-smokers to suffer a miscarriage in the first trimester...

January 3, 2010 - A study of about 1,300 Japanese women indicated that 32 percent of the women who smoked while being pregnant miscarried their baby comparing to only 4 percent of non-smokers.

This study offers one more reason for women to kick the smoking habit before becoming pregnant: a potentially reduced risk of early miscarriage.

PAPER: Risk factors of early spontaneous abortions among Japanese: a matched case–control study, Sachiko Baba, Hiroyuki Noda1, Masahiro Nakayama, Masako Waguri,
Nobuaki Mitsuda and Hiroyasu Iso (, Hum. Reprod - 1st published online 12/14/2010, ABSTRACT..

There are many reasons for women to quit smoking before becoming pregnant. The habit has been linked to increased risks of stillbirth, preterm delivery and low birthweight. But studies so far have come to conflicting conclusions as to whether smoking might contribute to miscarriage risk.

These latest findings support a connection.

For the study, researchers led by Dr. Sachiko Baba of Osaka University reviewed the records of 430 women who'd suffered a first-trimester miscarriage. They compared each woman with two others the same age who had given birth that same year. Overall, the researchers found, women who smoked heavily during pregnancy -- at least 20 cigarettes per day -- were more than twice as likely as the non-smokers to have a miscarriage. Seven percent (32) of the 430 women who suffered a miscarriage smoked that amount, versus four percent (36) of the 860 women who delivered a baby.

Previous research has led to estimates that up to eight percent of pregnancies end in miscarriage between six and eight weeks after the woman's last period, but after 10 weeks that rate drops to two percent.

Most miscarriages happen in the first trimester and experts believe that the majority of those are caused by random genetic abnormalities that cannot be prevented. However, certain lifestyle habits have been linked to a relatively increased risk of miscarriage -- including heavy drinking, drug use and, in some studies, smoking.

The current findings do not prove that smoking, itself, was the reason for the increased miscarriage risk seen in the study group. But the researchers were able to account for several other factors, including the women's reported drinking habits and histories of past miscarriages. And the smoking-miscarriage link remained.

Baba's team also found that women who worked during the first trimester were 65 percent more likely to have a miscarriage than those who did not work outside the home. Of women who suffered a miscarriage, one-third said they'd worked outside the home, compared with 19 percent of those who gave birth.

Some studies, Baba's team notes, have linked certain jobs with high physical demands or chemical exposures to miscarriage risk. One recent study, for instance, found that women exposed to anesthesia fumes in veterinary centers had a higher-than-average miscarriage risk. However, the researchers write, they know of no studies outside of Japan that have linked employment, as a whole, to an increased miscarriage risk.

According to the American College of Obstetricians and Gynecologists, there is no proof that working during pregnancy raises a woman's miscarriage risk.

An R.J. Reynolds Tobacco spokesman David Howard said in an e-mail that the company "agrees that women should not use snus or any tobacco product during pregnancy." (Pregnant - as recommended by R.J. Reynolds Tobacco don't use any tobacco product..)

Smoking during pregnancy..

References: Smoking tied to miscarriage risk, Reuters Health, SOURCE: Human Reproduction, online December 14, 2010, 12/30/2010; Smoking increases miscarriage risk, SJM/HRF,, 1/5/2011.