Table 4.
Plasma folate levels and unadjusted and adjusted odds of preterm birth (PTB) subtypes among predominantly urban, low-income, minority mother–infant dyads (n 2313) enrolled in the Boston Birth Cohort, USA, from 1998 to 2014
| Plasma folate level | Spontaneous PTB | Medically indicated PTB | ||||||
|---|---|---|---|---|---|---|---|---|
| ncases | % | aOR* | 95 % CI | ncases | % | aOR† | 95 % CI | |
| Continuous plasma folate concentration (nmol/l) | ||||||||
| Each unit increase | n/a | n/a | 0·995 | 0·990, 1·000 | n/a | n/a | 0·99 | 0·98, 0·99 |
| Each interquartile increase in folate level | n/a | n/a | 0·90 | 0·80, 1·01 | n/a | n/a | 0·73 | 0·62, 0·87 |
| Quartiles of plasma folate concentration (nmol/l) | ||||||||
| Lowest quartile: 6·6–19·4 (ref.) | 114 | 23·2 | 1·00 | n/a | 87 | 18·7 | 1·00 | n/a |
| Second quartile: 19·4–30·0 | 119 | 23·6 | 1·12 | 0·82, 1·53 | 73 | 15·9 | 0·85 | 0·60, 1·21 |
| Third quartile: 30·0–43·8 | 124 | 24·0 | 1·27 | 0·93, 1·73 | 61 | 13·4 | 0·68 | 0·47, 0·99 |
| Highest quartile: 43·8–185·5 | 96 | 18·1 | 0·86 | 0·62, 1·18 | 46 | 9·5 | 0·46 | 0·31, 0·69 |
| WHO classification (nmol/l) | ||||||||
| Insufficiency/deficiency: <13·5 | 45 | 22·5 | 0·77 | 0·53, 1·12 | 37 | 19·3 | 1·25 | 0·83, 1·86 |
| Normal: 13·5–45·3 (ref.) | 321 | 23·8 | 1·00 | n/a | 187 | 15·4 | 1·00 | n/a |
| Excess: ≥45·3 | 87 | 17·6 | 0·72 | 0·55, 0·95 | 43 | 9·5 | 0·58 | 0·40, 0·82 |
aOR, adjusted odds ratio; ref., reference category; n/a, not applicable.
*
Adjusted for maternal race, age, nativity, education, marital status, receipt of public assistance, parity, tobacco use, alcohol use, stress, BMI, pre-eclampsia disorders, intra-uterine infection/inflammation and diabetes.
†
Adjusted for maternal race, age, nativity, education, marital status, receipt of public assistance, parity, tobacco use, alcohol use and stress.