Table 2.
Breastfeeding in First Six Months of Life (Exclusively-breastfed vs. Formula-fed Only). Characteristics Among All Subjects, Among Subjects With PS in (0.350, 0.993), and Among Matched Pairs. Data From Project Viva
| Observed data | Observed data with 0.350<PS<0.993 |
Matched pairs (0.350<PS<0.993, Matching caliper= 0.05) |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Exclusively breastfed (311) |
Formula- fed only (126) |
Exclusively breastfed (223) |
Formula- fed only (53) |
Exclusively breastfed (276) |
Formula- fed only (276) |
|||||
| Maternal characteristics | ||||||||||
| N (%) | p* | N (%) | p* | N (%) | p# | |||||
| Age, years | <25 25–<35 >=35 |
8 (2.6) 198 (63.6) 105 (33.7) |
13 (10.3) 82 (65.1) 31 (24.6) |
<.01 | 5 (2.2) 141 (63.2) 77 (34.5) |
1 (1.9) 34 (64.2) 18 (34.0) |
0.98 | 8 (2.9) 172 (62.3) 96 (34.8) |
6 (2.2) 135 (48.9) 135 (48.9) |
0.48 |
| Education level | High school or less Some college BA/BS Grad school |
7 (2.3) 41 (13.2) 112 (36.1) 150 (48.3) |
18 (14.3) 47 (37.3) 43 (34.1) 18 (14.3) |
<.01 | 6 (2.7) 24 (10.8) 91 (40.8) 102 (45.7) |
2 (3.8) 12 (22.6) 25 (47.2) 14 (26.4) |
0.03 | 9 (3.3) 38 (13.8) 119 (43.1) 110 (39.9) |
3 (1.1) 32 (11.6) 130 (47.1) 111 (40.2) |
0.63 |
| Race/Ethnicity | Black Hispanic Other White |
25 (8.1) 9 (2.9) 26 (8.4) 250 (80.6) |
19 (15.1) 6 (4.8) 6 (4.8) 95 (75.4) |
0.07 | 13 (5.8) 8 (3.6) 14 (6.3) 188 (84.3) |
3 (5.7) 2 (3.8) 1 (1.9) 47 (88.7) |
0.65 | 15 (5.4) 17 (6.2) 18 (6.5) 226 (81.9) |
10 (3.6) 20 (7.3) 5 (1.8) 241 (87.3) |
0.34 |
| US Born | Yes | 260 (85.2) | 117 (94.4) | 0.03 | 199 (89.2) | 51 (96.2) | 0.12 | 242 (87.7) | 233 (84.4) | 0.75 |
| House hold income>US $70,000 |
216 (72.9) | 57 (49.1) | <.01 | 167 (74.9) | 39 (73.6) | 0.84 | 199 (72.1) | 242 (87.7) | 0.01 | |
| Pre-pregnancy BMI, kg/m2 |
<25 25–<30 >=30 |
224 (72.7) 66 (21.4) 18 (5.8) |
61 (48.4) 37 (29.4) 28 (22.2) |
<.01 | 157 (70.4) 52 (23.3) 14 (6.3) |
36 (67.9) 17 (32.1) 0 (0.0) |
0.10 | 190 (68.8) 70 (25.4) 16 (5.8) |
207 (75.0) 69 (25.0) 0 (0.0) |
|
| Gestational weight gain (IOM 2009 guideline) |
Inadequate Adequate Excessive |
34 (11.2) 99 (32.6) 170 (56.1) |
14 (11.2) 32 (25.6) 79 (63.2) |
0.33 | 24 (10.8) 63 (28.3) 136 (61.0) |
5 (9.4) 18 (34.0) 30 (56.6) |
0.71 | 33 (12.0) 79 (28.6) 164 (59.4) |
23 (8.3) 135 (48.9) 118 (42.8) |
0.26 |
| Mother herself was breastfed |
Yes | 129 (44.0) | 17 (14.7) | <.01 | 92 (41.3) | 11 (20.8) | <.01 | 110 (39.9) | 112 (40.6) | 0.97 |
| Maternal glucose tolerance status |
Gestational diabetes Impaired glucose tolerance Isolated hyperglycemia Normal |
10 (3.3) 8 (2.6) 28 (9.1) 261 (85.0) |
11 (8.8) 3 (2.4) 7 (5.6) 104 (83.2) |
0.07 | 7 (3.1) 5 (2.2) 21 (9.4) 190 (85.2) |
4 (7.6) 0 (0.0) 4 (7.6) 45 (84.9) |
0.33 | 13 (4.7) 5 (1.8) 23 (8.3) 235 (85.1) |
14 (5.1) 0 (0.0) 10 (3.6) 252 (91.3) |
|
| Smoking during pregnancy |
Former During pregnancy Never |
58 (19.2) 10 (3.3) 233 (77.4) |
29 (23.8) 24 (19.7) 69 (56.6) |
<.01 | 47 (21.1) 6 (2.7) 170 (76.2) |
15 (28.3) 2 (3.8) 36 (67.9) |
0.46 | 56 (20.3) 10 (3.6) 210 (76.1) |
122 (44.2) 4 (1.5) 150 (54.4) |
0.09 |
| Nullipara | 154 (49.5) | 39 (31.0) | 0.01 | 101 (45.3) | 19 (35.9) | 0.21 | 117 (42.4) | 84 (30.4) | 0.23 | |
| Paternal BMI, kg/m2 | <25 25–<30 >=30 |
122 (40.8) 145 (48.4) 32 (10.7) |
27 (22.7) 65 (54.6) 27 (22.7) |
<.01 | 82 (36.8) 116 (52.0) 25 (11.2) |
12 (22.6) 33 (62.3) 8 (15.1) |
0.14 | 93 (33.7) 149 (54.0) 34 (12.3) |
81 (29.4) 176 (63.8) 19 (6.9) |
0.34 |
| Father US born | Yes | 255 (84.7) | 103 (90.4) | 0.14 | 192 (86.1) | 50 (94.3) | 0.10 | 239 (86.6) | 244 (88.4) | 0.82 |
| Child characteristics | ||||||||||
| Female sex | 159 (51.1) | 66 (52.4) | 0.81 | 117 (52.5) | 27 (50.9) | 0.84 | 141 (51.1) | 124 (44.9) | 0.58 | |
| Cesarean section | 51 (16.5) | 34 (27.0) | 0.01 | 39 (17.5) | 9 (17.0) | 0.93 | 47 (17.0) | 46 (16.7) | 0.96 | |
| Mean (SD) | p* | Mean (SD) | p* | Mean (SD) | p# | |||||
| Birth weight for gestational age z- score |
0.3 (0.9) | 0.21 (0.9) | 0.34 | 0.4 (0.9) | 0.3 (0.8) | 0.56 | 0.3 (0.9) | 0.4 (0.8) | 0.77 | |
| Gestational age at birth, weeks | 39.8 (1.3) | 39.4 (1.5) | <.01 | 39.9 (1.4) | 39.7 (1.4) | 0.25 | 39.9 (1.4) | 39.4 (1.4) | 0.13 | |
| Census-derived socio-economic status variables, expressed as percent of census tract population (Census 2000 data) | ||||||||||
| % 25 years or older with no high school diploma |
9.3 (8.7) | 9.2 (8.5) | 0.94 | 7.9 (7.4) | 6.6 (5.5) | 0.15 | 8.3 (7.8) | 6.5 (5.3) | 0.16 | |
| % 25 years or older with college degree and above |
47.2 (20.1) | 31.0(15.1) | <.01 | 45.9 (17.9) | 38.4(13.4) | <.01 | 43.6 (17.9) | 44.7(14.5) | 0.71 | |
| % below poverty line (1999 dollars) |
10.4 (9.2) | 6.1 (6.2) | <.01 | 11.1 (9.4) | 7.8 (6.1) | <.01 | 10.3 (9.2) | 9.8 (5.8) | 0.17 | |
| % households with 1999 income below $20,000 |
16.9 (9.7) | 18.7(10.3) | 0.09 | 15.6 (8.8) | 15.3 (7.9) | 0.85 | 15.9 (9.3) | 15.5 (7.3) | 0.79 | |
| % household with 1999 income $150,000 and above |
11 (8.6) | 14.4 (9.1) | <.01 | 10.9 (8.2) | 11.2 (5.5) | 0.81 | 11.6 (8.8) | 9.9 (5.1) | 0.69 | |
*
p-value from chi-square test or t-test
#
p-value from generalized score tests for Type III contrasts from PROC GENMOD to adjust for repeated use of the same subjects since matching was done with replacement