BOCA RATON, FLA. — In a pilot study of pregnant women who continued to smoke cigarettes despite knowing they were pregnant, 11 (37%) of 30 women who received contingency management achieved abstinence, compared with just 2 (10%)) of 23 women who did not.
This result highlights the effectiveness of contingency management as a strategy to help pregnant women stop smoking, Dr. Sarah Heil said at the annual meeting of the American Academy of Addiction Psychiatry.
The women in both the contingent group and noncontingent group were seen every day for the first 5 days of the study.
During this time, abstinence was based on a breath carbon monoxide level of 6 parts per million or less, said Dr. Heil of the University of Vermont, Burlington.
After the first 5 days, the women were seen according to the following schedule:
▸ Twice a week for 7 weeks.
▸ Once a week for the next 11 weeks.
▸ Once every other week until delivery.
▸ Once a week for the first 4 weeks post partum.
▸ Every other week for the next 8 weeks.
Abstinence in this phase of the study was assessed by measuring urine cotinine levels; levels of 80 ng/mL or less were indicative of abstinence.
The women were rewarded with vouchers, which were earned contingent on biochemically verified abstinence.
The voucher value began at $6.25 and escalated at a rate of $1.25 per consecutive negative sample up to a maximum of $45.
“These vouchers are like having a bank account with us. We put their money into an account, and they are allowed to spend it on things we believe are appropriate. So there were a lot of gift certificates, paying of credit card bills, and shopping at Wal-Mart and grocery stores,” Dr. Heil said.
Women who were randomized to noncontingency management got vouchers independent of their smoking status.
The vouchers were a flat $11.50 per antepartum visit, and $20 per each postpartum visit.
The women in the study had been smoking for about 8 years; most of them lived with other smokers.
They smoked approximately one pack of cigarettes a day before pregnancy, but had reduced this amount by roughly 50% by the time they entered the study.
“They had very high intentions to quit while they are pregnant,” Dr. Heil noted.
Most of the women had less than a high school education, and few of the women were married.
To be considered abstinent at each time point, the women had to self-report that they had not had a cigarette—“not even a puff”—in the last 7 days, as well as the appropriate urine cotinine level.
The effects obtained in the study persisted 3 months after delivery, and for a further 3 months, even though the voucher program was discontinued at 3 months post partum.
This was true for women in the contingent and noncontingent groups, Dr. Heil said.
Importantly, fetuses in the contingent group gained weight faster than those in the noncontingent group. Fetal weight was estimated by measuring fetal length and abdominal circumference by ultrasound.
“We are really excited by these results,” she said.
Cigarette smoking is the leading preventable cause of poor pregnancy outcomes in the United States.
Placental abruptions, small gestational age, preterm and still birth, low birth weight, and increased risk for sudden infant death syndrome are all associated with cigarette smoking by the mother.
The adverse effects of smoking on the neonate cost $1,630/birth per year in 2008 dollars.
Dr. Heil said she hopes to extend her research on contingency management to include pregnant smokers who are also opioid dependent.
The women were rewarded with vouchers—earned contingent on biochemically verified abstinence. DR. HEIL