Are women with an unintended pregnancy less likely to breastfeed?

Table 1 shows characteristics of mothers and infants by breastfeeding behavior. Women who breastfed, both initially and for at least 16 weeks, were older at conception and had had more years of education than women who did not breastfeed at all. They were more likely to be white and less likely to be black. A similar percentage of women in each group were Hispanic. Percentage of the poverty level, a proxy for socioeconomic status, was higher for those who breastfed at all, but similar for those who continued breastfeeding and those who did not breastfeed. Rates of prenatal care and mean weeks at first prenatal visit were similar in all groups. Among women who were employed during their pregnancies, almost two thirds took maternity leave, regardless of breastfeeding behavior. Mean length of maternity leave was 3.4 weeks longer among women who continued to breastfeed than among women who did not breastfeed at all. The percentage of vaginal deliveries was similar among groups. Both premature and low birth weight infants were more common among women who did not breastfeed.

The association between the intendedness of pregnancy and breastfeeding behavior is reported in Table 2. Crude odds ratios show that women with any type of unintended pregnancy were more likely not to initiate breastfeeding than women whose pregnancies were intended. Some, but not all, of this association can be attributed to confounding by demographic factors. Having an unintended pregnancy was not associated with any significant difference in the initiation of breastfeeding, after adjusting for age, race, marital status, poverty level, and education. While women with mis-timed pregnancies were as likely to initiate breastfeeding as those whose pregnancies were intended (OR = 1.03; 95% CI, 0.88-1.21), women with unwanted pregnancies were more likely not to start breastfeeding (OR = 1.76; 95% CI, 1.26-2.44).

Table 2 also describes the association between pregnancy intention status and the continuation of nonexclusive breastfeeding for at least 16 weeks. In contrast to the initiation of breastfeeding, duration of breastfeeding was affected by the intendedness of pregnancy in every comparison. Adjusted odds ratios show that women with either type of unintended pregnancy were more likely not to continue breastfeeding than those with intended ones (OR = 1.28; 95% CI, 1.06-1.54). As with breastfeeding initiation, this association is being driven by the unwanted pregnancies. Women with unwanted pregnancies were more likely not to continue breastfeeding (OR = 1.69; 95% CI, 1.12-2.55).

Each of these associations was then evaluated for effect modification. As seen in Table 3, only race was an important factor. In the total sample, 56.3% of white women, 55.4% of Hispanic women, and 24.7% of black women breastfed at all; and 41.6%, 41.2%, and 12.6% of white, Hispanic, and black women breastfed for at least 16 weeks. White women with unwanted pregnancies were more likely not to initiate breastfeeding (OR = 2.50; 95% CI, 1.54-4.05) and more likely not to continue breastfeeding (OR = 2.56; 95% CI, 1.34-4.87) than white women with intended pregnancies. These differences in breastfeeding behaviors for unwanted pregnancies were not seen for either Hispanic or black women. For each stratified analysis, a single P value for heterogeneity was calculated to compare white women with non-white women (Hispanic and black women combined). The only significant difference by race was for unwanted pregnancies. The P value for heterogeneity was 0.01 for both initiation and continuation of breastfeeding. Stratified analyses for age, marital status, education, poverty level, and year of birth showed similar odds ratios across strata and nonsignificant P values for heterogeneity in every case (analyses not shown).

TABLE 1
Characteristics of mothers and infants by breastfeeding status (n=6733)

TABLE 2
Unintended pregnancy and breastfeeding behavior in the United States