Table 1.
Study participants in the Lifestyle During Pregnancy Study distributed by maternal and child characteristics and by breastfeeding duration (n=1385)
| Overall | Breastfeeding duration | P* | |||||
| ≤1 month | 2–3 months | 4–6 months | 7–9 months | ≥10 months | |||
| Maternal age at pregnancy (years)† | 30.9 (4.4) | 30.9 (4.5) | 29.9 (4.4) | 30.1 (4.2) | 30.9 (4.1) | 32.0 (4.3) | <0.0001 |
| Parity† | 0.0003 | ||||||
| Nulliparous | 676 (48.8) | 80 (57.6) | 82 (56.2) | 122 (49.0) | 194 (49.0) | 198 (43.5) | |
| One child | 467 (33.7) | 41 (29.5) | 50 (34.3) | 88 (35.3) | 142 (35.9) | 146 (32.1) | |
| ≥2 children | 242 (17.5) | 18 (13.0) | 14 (9.6) | 39 (15.7) | 60 (15.2) | 111 (24.4) | |
| Prepregnancy BMI (kg/m2)† | 22.6 (4.5) | 22.8 (4.1) | 23.3 (4.7) | 22.7 (4.7) | 22.6 (4.0) | 22.2 (4.3) | <0.0001 |
| Marital status† | 0.3 | ||||||
| Single | 37 (2.7) | 4 (2.9) | 2 (1.4) | 11 (4.4) | 7 (1.8) | 13 (2.9) | |
| Cohabiting with partner | 1348 (97.3) | 135 (97.1) | 144 (98.6) | 238 (95.6) | 389 (98.2) | 442 (97.1) | |
| Alcohol, drinks/week in pregnancy† | 0.5 (2.0) | 0.5 (2.0) | 0.5 (2.0) | 0.5 (2.0) | 0.5 (2.0) | 0.5 (2.0) | 0.3 |
| Smoking in pregnancy† | <0.0001 | ||||||
| Yes | 444 (32.1) | 54 (38.9) | 66 (45.2) | 91 (36.6) | 102 (25.8) | 131 (28.8) | |
| No | 941 (67.9) | 85 (61.2) | 80 (54.8) | 158 (63.5) | 294 (74.2) | 324 (71.2) | |
| Postnatal smoking† | <0.0001 | ||||||
| Yes | 449 (32.4) | 51 (36.7) | 74 (50.7) | 97 (39.0) | 98 (24.8) | 129 (28.4) | |
| No | 936 (67.6) | 88 (63.3) | 72 (49.3) | 152 (61.0) | 298 (75.3) | 326 (71.7) | |
| Maternal IQ† | 100.0 (14.9) | 100.4 (14.9) | 94.3 (14.8) | 97.1 (13.8) | 102.2 (14.0) | 103.3 (14.9) | <0.0001 |
| Parental education (years)† | 13.0 (3.0) | 13.0 (3.5) | 12.3 (3.0) | 12.5 (2.5) | 13.0 (2.5) | 13.5 (2.5) | <0.0001 |
| Child sex† | 0.5 | ||||||
| Girls | 654 (47.2) | 74 (53.2) | 66 (45.2) | 115 (46.2) | 178 (45.0) | 221 (48.6) | |
| Boys | 731 (52.8) | 65 (46.8) | 80 (54.8) | 134 (53.8) | 218 (55.1) | 234 (51.4) | |
| Gestational age at birth (weeks)† | 40.1 (1.5) | 40.1 (1.7) | 39.8 (1.7) | 40.0 (1.5) | 40.2 (1.5) | 40.1 (1.4) | 0.3 |
| Birth weight z-score† | 0.00 (0.97) | 0.02 (0.98)) | −0.22 (0.93) | 0.01 (0.95) | −0.01 (0.90) | 0.11 (1.00) | 0.005 |
*P value from χ2 test (categorical variables: parity, marital status, smoking in pregnancy, postnatal smoking, child sex), F-test one way analysis of variance (normally distributed variables: maternal age, maternal IQ, gestational age, z-score for birth weight) or Kruskal-Wallis test (non-normally distributed variables: prepregnancy BMI, alcoholic drinks/week in pregnancy, parental education).
Values are mean (SD) (for normally distributed variables: maternal age, maternal IQ, gestational age, z-score for birth weight), median (IQR) (for non-normally distributed variables: prepregnancy BMI, alcoholic drinks/week in pregnancy, parental education) or n (%) (for categorical variables: parity, marital status, smoking in pregnancy, postnatal smoking, child sex).
BMI, body mass index.