Table 2. Characteristics of participants’ serum total and active B12 and plasma folate and homocysteine concentrations in early pregnancy and in cord blood sampled at birtha,b,c.
| Maternal early pregnancy n = 3176 | Cord blood n = 2714 | |
|---|---|---|
| Serum total B12 concentration (pmol/L) | 173.0 (76.0,414.0) | 303.0 (120.0, 901.8) |
| 1 SDS (pmol/L) | 92.2 | 200.1 |
| ≥145 (pmol/L), n (%) | 1972 (66.1) | 2516 (94.4) |
| <145 (pmol/L), n (%) | 1011 (33.9) | 149 (5.6) |
| Serum active B12 concentration (pmol/L2) | 42.0 (18.0, 98.3) | 87.0 (37.0, 128.0) |
| 1 SDS (pmol/L) | 20.1 | 29.0 |
| ≥21 pmol/L, n (%) | 2092 (95.6) | 2545 (99.8) |
| <21 pmol/L, n (%) | 96 (4.4) | 6 (0.2) |
| Plasma folate concentration (nmol/L) | 17.2 (6.0, 37.8) | 20.7 (10.6, 38.5) |
| 1 SDS (nmol/L) | 9.0 | 7.6 |
| ≥8 nmol/L, n (%) | 2795 (89.6) | 2631 (99.8) |
| <8 nmol/L, n (%) | 325 (10.4) | 6 (0.2) |
| Plasma homocysteine concentration (μmol/L) | 6.9 (4.7, 12.0) | 9.0 (5.1, 16.2) |
| 1 SDS (μmol/L) | 2.0 | 2.9 |
| <19 μmol/L, n (%) | 3080 (99.6) | 2534 (99.1) |
| ≥19 μmol/L, n. (%) | 13 (0.4) | 22 (0.9) |
| Folic acid supplement use | ||
| No, n (%) | 622 (21.0) | – |
| From early pregnancy, n (%) | 956 (32.3) | – |
| Yes, from preconception, n (%) | 1385 (46.7) | – |
SDS standard deviation score.
Values are based on observed, not imputed data and are median (95% range) for continuous variables and numbers (%) for categorical variables.
Reference values for deficient folate and total and active B12 status, or high homocysteine status during pregnancy are not available and we therefore applied the 95% reference intervals of healthy adults, which were established by the department of clinical chemistry. Table 2 shows that for early pregnancy circulating active B12 and homocysteine concentrations, and cord blood total and active B12, folate and homocysteine concentrations, the groups with suboptimal concentrations were too small for analyses.
Maternal circulating one-carbon metabolism markers were available in n = 2983 (total B12), n = 2188 (active B12), n = 3120 (folate) and n = 3093 (homocysteine), respectively. Cord blood one-carbon metabolism markers were available in n = 2665 (total B12), n = 2551 (active B12), n = 2637 (folate) and n = 2556 (homocysteine), respectively. Information on folic acid supplement use was available in 2963 mothers with information on maternal folate concentrations in early- pregnancy.