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Risk Factors for not Breastfeeding at 10 Weeks, Oregon, 1998-99

Kenneth D. Rosenberg, MD, MPH, Zhiwei Yu, Alfredo Sandoval Jr., MS, MBA
Oregon Health Division, Portland, Oregon
American Public Health Association, 129th Annual Meeting, October 22, 2001


Breastfeeding benefits mothers and babies. The American Academy of Pediatrics recommends breastfeeding for 12 months. The major barriers to long-term breastfeeding occur when mothers seek to return to work or school, typically when the baby is 4-16 weeks old. There is little information about breastfeeding in this period.


Oregon PRAMS surveys a stratified random sample of Oregon resident mothers after a live birth. This data comes from women 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) and non-response.

Women were asked "For how many weeks did you breast-feed your new baby?" [Answer options: Didn't breast-feed; Less than 1 week; still breast-feeding or ___ Weeks.]

Women were counted as breastfeeding at 10 weeks if they said that they were still breastfeeding or if they had breastfed for 10 or more weeks.

Over 99% of PRAMS surveys are completed after the baby is 10 weeks old.


1867/2855 women responded (response rate = 65.4%).
83.6% of Oregon women initiated breastfeeding.
59.5% of Oregon women were still breastfeeding (not necessarily exclusively breastfeeding) by the time the baby was 10 weeks old.
In a multivariate model, the only significant predictor of women not breastfeeding at 10 weeks was smoking in the third trimester of pregnancy.

Table 1. Risk Factors for Not Breastfeeding at 10 weeks Postpartum, Oregon PRAMS 1998-1999: UNIVARIATE ANALYSIS

Maternal Characteristic Odds Ratio (95% CI)
Tobacco Use (third trimester)(A) 2.08 (1.49, 2.94)
Unmarried (B) 2.00 (1.04, 2.44)
Maternal Age <20 years (C) 1.96 (1.27, 3.03)
WIC Enrolled (D) 1.61 (1.18, 2.22)
Medicaid (E) 1.59 (1.04, 2.44)
Annual Family Income <$30,000 (F) 1.52 (1.10, 2.08)
Birth Weight <2500g (G) 1.47 (1.11, 1.96)
Unintended Pregnancy (H) 1.47 (1.05, 2.04)

(A) compared to no tobacco use in third trimester
(B) compared to married
(C) compared to maternal age > =20 yrs
(D) compared to not enrolled in WIC during pregnancy
(E) compared to no Medicaid coverage just before became pregnant
(F) compared to annual family income > =$30,000
(G) compared to Birth Weight > =2500g
(H) compared to intended pregnancy

Table 2. Risk Factors for Not Breastfeeding at 10 weeks Postpartum, Oregon PRAMS 1998-1999: MULTIVARIATE ANALYSIS

Maternal Characteristic Odds Ratio (95% CI)
Tobacco Use (third trimester)(A) 1.92 (1.33, 2.78)
Maternal Age <20 years (B) 1.59 (0.93, 2.70)
Unmarried (C) 1.35 (0.88, 2.04)
Unintended Pregnancy (D) 1.16 (0.81, 1.67)

(A) compared to no tobacco use in third trimester
(B) compared to maternal age > =20 yrs
(C) compared to married
(D) compared to intended pregnancy

DISCUSSION (with help from Bill Letson)

This analysis leads to the conclusion that programs for breastfeeding support should be targeted at women who smoke during pregnancy.

The importance of maternal smoking is supported by parallel work that we have done linking newborn screening (containing infant feeding data) and birth certificates.

Mascola et al. found that breastfed infants of smoking mothers had ten-fold higher cotinine levels than bottle fed infants of smoking mothers. 1 There is also evidence of reduced breast milk output as a result of maternal smoking. 2 , 3

It is likely that interventions to further discourage mothers from prenatal and postpartum smoke exposure will be helpful in efforts to enhance breastfeeding.

1. Mascola MA, Van Vunakis H, Tager IB, Speizer FE, Hanrahan JP. Exposure of young infants to environmental tobacco smoke: Breast-feeding among smoking mothers. Am J Public Health. 1998;88:893-896.
2. Horta BL, Victora CG, Menezes AM, Barros FC. Environmental tobacco smoke and breastfeeding duration. Am J Epidemiol. 1997;146:1128-1133.
3. Ratner PA, Johnson JL, Bottorff JL. Smoking relapse and early weaning among postpartum women: Is there an association? Birth. 1999;26:76-82.