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Oregon PRAMS Presentation

Oregon PRAMS: Presentations

Association Between Maternal Smoking and Breastfeeding at 10 Weeks


Introduction | Background | Methods I | Methods II | Results I | Results II | Conclusions |
Public Health Implications


Association Between Maternal Smoking and
Breastfeeding at 10 Weeks


Kenneth D. Rosenberg, MD, MPH
Zhiwei Yu, MPH
Alfredo P. Sandoval, MS, MBA

8th Annual MCH Epidemiology Conference
December 13, 2002
Clearwater Beach, Florida
NOTES: I want to acknowledge my co-authors: Zhiwei Yu, who came to us through the Graduate Student Internship Program & Al Sandoval, who is the Oregon PRAMS Project Coordinator


Introduction:

Maternal smoking:
  Associated with decreased breastfeeding
Hakansson et al. (Scand J Prim Health Care 1992;10:60-65): 44% longer.
Horta et al. (Am J Epidemiol 1997;146:1128-1133): smoking not associated
  with BF initiation but associated with BF duration.

NOTES: Maternal smoking may be associated with decreased likelihood of initiating breastfeeding and decreased duration of breastfeeding.
Hakansson et al (Scand J Prim Health Care. 1992;10:60-65) found that infants of non-smoking mothers breastfed 44% longer than infants of smoking mothers.
Horta et al (Am J Epidemiol. 1997;146:1128-1133) found no association between smoking and breastfeeding initiation but a strong association between smoking and breastfeeding duration.


Background:

Maternal smoking: before, during or after pregnancy?
PRAMS:
  sample size
  asks about smoking before, during and after pregnancy

NOTES: Because most women who smoke during pregnancy also smoke before and after pregnancy, it?s been difficult to know which time periods are most strongly associated with decreases in breastfeeding.
PRAMS has a large sample size and asks about maternal smoking before, during and after pregnancy.
Knowing when smoking is associated with decreased breastfeeding might help explain the mechanism by which smoking causes decreased breastfeeding.
It might also help smoking cessation programs to target their programs.


Methods I:

Oregon PRAMS
  Stratified random sample of Oregon resident mothers
  Year 1: babies born 8/1/98-8/9/99.
  Weighted for oversampling, nonresponse and noncoverage.
  Duration of breastfeeding:
    "For how many weeks did you breast-feed your new baby?"
  Over 99% completed: after baby 10 weeks old.

NOTES: Oregon PRAMS (Pregnancy Risk Assessment Monitoring System) surveys a stratified random sample of Oregon resident mothers 2-6 months after a live birth.
This data comes from our first 12 months.
Women were surveyed from November 1998 through October 1999; the babies were born 8/1/98-8/9/99.
Responses were weighted for oversampling (race/ethnicity and low birthweight), nonresponse and noncoverage.
The duration of breastfeeding was assessed by asking
   "For how many weeks did you breast-feed your new baby?"
Over 99% of PRAMS responses occurred after the baby was 10 weeks old.


Methods II:

PRAMS:
Smoking before, during and after pregnancy.

Before = in the 3 months before pregnancy
During = in the last 3 months of pregnancy
After = smoking now (10-26 weeks after birth)

NOTES: PRAMS asks women about their smoking before, during and after pregnancy.
Before is measured by whether they smoked in the 3 months before pregnancy.
During is measured by whether they smoked in the last 3 months of pregnancy.
After is measured by whether they were smoking at the time they answered the survey (10-26 weeks after birth).


Results I:

Response rate: 1867/2919 = 64.0%

83.6% of women initiated breastfeeding.

59.5% of women were still breastfeeding at 10 weeks old.

NOTES: Of 2919 women surveyed,
1867 responded (response rate = 64.0%).
83.6% of Oregon women initiated breastfeeding.
59.5% of Oregon women were still breastfeeding at the time the baby was 10 weeks old.


Results II:

Strength of Association Between Time of Maternal Smoking and Not Breastfeeding at 10 weeks (multivariate)

Time of Smoking ORa 95% CI
        
Before Pregnancy*
   Smokers 2.17 1.47, 3.23
During Pregnancy**
   Smokers 1.85 1.11, 3.13
After Pregnancy***
   Smokers 2.56 1.64, 4.00

For all 3 times: reference is non-smokers
*Before = in the 3 months before pregnancy
**During = in the last 3 months of pregnancy
***After = smoking now (10-26 weeks after birth

NOTES: We ran univariate analysis of covariates
and found 4 that were associated with increased risk of not breastfeeding at 10 maternal weeks:
   maternal smoking,
   maternal age < 20 years,
   unmarried, &
   unintended pregnancy
We then ran a logistic model using each of the PRAMS smoking variables: before, during and after.
What we found was that smoking after pregnancy was most strongly associated with not breastfeeding at 10 weeks.
Compared with non-smokers, women who were smoking after pregnancy were 2.5 times more likely to have not been breastfeeding when the baby was 10 weeks old.


Conclusions:

Maternal smoking: associated with decreased breastfeeding

Parallel work: Letson GW, Rosenberg KD and Wu L. Asoociation
   between smoking during pregnancy and breastfeeding at about
   two weeks of age in Oregon, 1998. Journal of Human Lactation.
   2002;18:368-372

Maternal exposure to nicotine decreases breast milk output.

Smoking mothers may have lower milk output and lower prolactin
   levels than nonsmoking mothers

NOTES: Maternal smoking, especially smoking after pregnancy, is associated with decreased breastfeeding at 10 weeks.
This is supported by parallel work that we have done linking newborn metabolic screening (containing infant feeding data) and birth certificate data.
Maternal exposure to nicotine decreases breast milk output.
These findings are biologically plausible because smoking mothers may have lower milk output and lower prolactin levels than nonsmoking mothers.


Public Health Implications:

Assist pregnant women who wish to stop smoking

Helping mothers to quit smoking: should
   increase breastfeeding duration

Breastfeeding support programs

NOTES: There is a need for more programs to assist pregnant women who wish to stop smoking.
Helping mothers to quit smoking should increase infant health in many ways, including increasing breastfeeding duration.
Breastfeeding support programs should expect that women who smoke may need supplemental support to continue breastfeeding.


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