TABLE 1

Family, Maternal, Infant, and Medical Characteristics: Infant Cohort at 9 Months

Ever Breastfed (N = 5940)Never Breastfed (N = 3914)P
n (%)n (%)
Resident spouse/partner (yes)5469 (92.1)3213 (82.1)≤.001
Social class≤.001
 Professional/managerial3486 (58.7)1449 (37.0)
 Nonmanual/skilled manual1533 (25.8)1419 (36.3)
 Semiskilled/unskilled505 (8.5)397 (10.1)
 Unknown/never worked416 (7.0)649 (16.6)
Medical card status (yes)1336 (22.8)1433 (36.6)≤.001
Maternal education≤.001
 Primary level/no education65 (1.1)152 (3.9)
 Second level1782 (30.0)2269 (58.0)
 Third level4093 (68.9)1493 (38.1)
Maternal working status (yes)4828 (81.3)2865 (73.2)≤.001
Maternal age, y≤.001
 ≤ 24456 (7.7)653 (16.7)
 25–291178 (19.8)883 (22.6)
 30–34 y2202 (37.1)1240 (31.7)
 ≥35 y2104 (35.4)1138 (29.1)
Maternal ethnicity (Irish)4209 (70.9)3725 (95.2)≤.001
Maternal depression (yes)222 (3.7)201 (5.3).001
Smoking in dwelling during pregnancy (yes)1535 (25.8)1646 (42.1)≤.001
Delivery mode (cesarean)1348 (22.7)1063 (27.2)≤.001
Birth weight (≥2500 g; yes)5842 (98.4)3810 (97.3)≤.001
Visit to the NICU (yes)575 (9.7)420 (10.7).090
Infant sex (boy)2944 (49.6)2047 (52.3).008
Siblings living in dwelling (yes)3248 (54.7)2614 (66.8)≤.001
  • Medical card coverage is a means-tested card issued by health services on the basis of financial need. There are 2 tiers of medical card coverage: “full coverage,” which includes visits to general practitioners plus prescriptions and “general practitioner only coverage,” which excludes prescriptions. Regarding the maternal education variable, primary level/no formal education is approximately equivalent to having an elementary to middle school education in the US system; second level is approximately equivalent to a high school diploma or technical trade/vocational diploma in the US system; and third level is equivalent to a college or bachelor’s degree, graduate degree, or doctorate. Maternal working status refers to employment before pregnancy. Categorization of maternal depression refers to a score of ≥11 on the Center for Epidemiologic Studies Depression Scale.