Table 3.
Use of iodine-containing supplements and pregnancy and birth outcomes
| Number | Crude models | Adjusted modelsa | Restricted controlsb | |||
|---|---|---|---|---|---|---|
| Odds ratio (95% CI) | p value | Odds ratio (95% CI) | p value | Odds ratio (95% CI) | ||
| Intrauterine death | 270/78,318 (0.34%) | |||||
| Any iodine supplement use GW 0–20 | 29,131 | 0.80 (0.62, 1.03) | 0.089 | 0.78 (0.61, 1.02) | 0.071 | 0.96 (0.64, 1.45) |
| First report of iodine supplement | ||||||
| Never (non-supplement user) | 49,187 (13,451b) | 1 (ref.) | 1 (ref.) | 1 (ref.) | ||
| Before pregnancyc | 7477 | 0.79 (0.51, 1.23) | 0.30 | 0.76 (0.48 1.19) | 0.23 | 0.92 (0.53, 1.62) |
| GW 0–12 | 7149 | 0.94 (0.62, 1.42) | 0.77 | 0.92 (0.60, 1.40) | 0.70 | 1.11 (0.63, 1.94) |
| GW > 12 | 5253 | 0.77 (0.45, 1.30) | 0.32 | 0.76 (0.45, 1.29) | 0.31 | 0.78 (0.38, 1.60) |
| Preeclampsia | 2936/78,318 (3.8%) | |||||
| Any iodine supplement use GW 0–20 | 29,131 | 0.98 (0.91, 1.06) | 0.64 | 0.93 (0.86, 1.01) | 0.098 | 0.94 (0.84, 1.06) |
| First report of iodine supplement | ||||||
| Never (non-supplement user) | 49,187 (13,451b) | 1 (ref.) | 1 (ref.) | 1 (ref.) | ||
| Before pregnancyc | 7477 | 0.88 (0.77, 1.01) | 0.067 | 0.85 (0.74, 0.98) | 0.022 | 0.84 (0.71, 1.00) |
| GW 0–12 | 7149 | 1.05 (0.92, 1.19) | 0.48 | 0.96 (0.84, 1.10) | 0.58 | 0.97 (0.82, 1.14) |
| GW > 12 | 5253 | 0.99 (0.86, 1.15) | 0.93 | 0.93 (0.80, 1.08) | 0.35 | 0.91 (0.76, 1.11) |
| Preterm delivery (< GW 37) | 3889/77,995 (5.0%) | |||||
| Any iodine supplement use GW 0–20 | 29,014 | 1.00 (0.93, 1.07) | 0.98 | 0.97 (0.91, 1.04) | 0.42 | 1.07 (0.96, 1.18) |
| First report of iodine supplement | ||||||
| Never (non-supplement user) | 48,981 (13,405b) | 1 (ref.) | 1 (ref.) | 1 (ref.) | ||
| Before pregnancyc | 7445 | 1.07 (0.96, 1.20) | 0.21 | 1.05 (0.94, 1.18) | 0.35 | 1.18 (1.03, 1.36) |
| GW 0–12 | 7126 | 1.02 (0.91, 1.14) | 0.70 | 0.99 (0.88, 1.11) | 0.82 | 1.08 (0.94, 1.25) |
| GW > 12 | 5230 | 1.02 (0.90, 1.17) | 0.71 | 0.99 (0.87, 1.13) | 0.86 | 1.04 (0.89, 1.23) |
| Early preterm delivery (< GW 32) | 612/77,995 (0.78%) | |||||
| Any iodine supplement use GW 0–20 | 29,014 | 0.82 (0.69, 0.97) | 0.020 | 0.80 (0.67, 0.95) | 0.010 | 0.82 (0.64, 1.05) |
| First report of iodine supplement | ||||||
| Never (non-supplement user) | 48,981 (13,405b) | 1 (ref.) | 1 (ref.) | 1 (ref.) | ||
| Before pregnancyc | 7445 | 0.94 (0.72,1.24) | 0.67 | 0.94 (0.71, 1.24) | 0.66 | 0.98 (0.71, 1.38) |
| GW 0–12 | 7126 | 0.83 (0.62,1.12) | 0.22 | 0.80 (0.60, 1.08) | 0.14 | 0.73 (0.51, 1.08) |
| GW > 12 | 5230 | 0.61 (0.41, 0.90) | 0.014 | 0.59 (0.40, 0.87) | 0.008 | 0.62 (0.39, 0.98) |
| Spontaneous preterm delivery (< GW 37) | 2211/76,313 (2.8%) | |||||
| Any iodine supplement use GW 0–20 | 28,406 | 1.03 (0.95, 1.13) | 0.45 | 1.00 (0.91, 1.09) | 0.93 | 1.09 (0.95, 1.25) |
| First report of iodine supplement | ||||||
| Never (non-supplement user) | 47,907 (13,196b) | 1 (ref.) | 1 (ref.) | 1 (ref.) | ||
| Before pregnancyc | 7273 | 1.08 (0.94, 1.25) | 0.28 | 1.07 (0.92, 1.24) | 0.39 | 1.20 (1.00, 1.44) |
| GW 0–12 | 6977 | 1.08 (0.93, 1.25) | 0.31 | 1.02 (0.88, 1.19) | 0.75 | 1.12 (0.93, 1.35) |
| GW > 12 | 5123 | 1.09 (0.93, 1.29) | 0.29 | 1.04 (0.88, 1.23) | 0.65 | 1.12 (0.91, 1.38) |
| Beta (95% CI) | Beta (95% CI) | Beta (95% CI) | ||||
| Birth weight | 78,210 | |||||
| Any iodine supplement use GW 0–20 | 29,091 | − 11.0 (− 19.4, − 2.7) | 0.009 | 13.6 (5.6, 21.7) | 0.001 | 3.3 (−8.3, 14.8) |
| First report of iodine supplement | ||||||
| Never (non-supplement user) | 49,119 (13,435b) | 0 (ref.) | 0 (ref.) | 0 (ref.) | ||
| Before pregnancyc | 7462 | − 5.1 (− 19.1, 8.9) | 0.48 | 16.3 (2.7, 29.9) | 0.019 | 7.5 (− 9.0, 23.9) |
| GW 0–12 | 7139 | − 12.4 (− 26.4, 1.6) | 0.084 | 19.6 (6.0, 33.1) | 0.005 | 9.7 (− 6.8, 26.2) |
| GW > 12 | 5248 | − 11.7 (− 27.7, 4.3) | 0.15 | 16.8 (1.4, 32.2) | 0.033 | 12.0 (− 6.5, 30.4) |
| Birth weightz-score | 77,949 | |||||
| Any iodine supplement use GW 0–20 | 28,998 | − 0.03 (− 0.04, − 0.01) | 0.001 | 0.03 (0.01, 0.04) | < 0.001 | 0.01 (− 0.01, 0.03) |
| First report of iodine supplement | ||||||
| Never (non-supplement user) | 48,951 (13,393b) | 0 (ref.) | 0 (ref.) | 0 (ref.) | ||
| Before pregnancyc | 7439 | 0.00 (−0.02, 0.03) | 0.88 | 0.05 (0.03, 0.07) | < 0.001 | 0.04 (0.01, 0.07) |
| GW 0–12 | 7121 | − 0.03 (− 0.05, − 0.00) | 0.043 | 0.04 (0.02, 0.07) | < 0.001 | 0.03 (0.00, 0.06) |
| GW > 12 | 5229 | − 0.04 (− 0.07, − 0.02) | 0.002 | 0.02 (− 0.01, 0.05) | 0.13 | 0.01 (− 0.02, 0.05) |
| Odds ratio (95% CI) | Odds ratio (95% CI) | Odds ratio (95% CI) | ||||
| SGA | 7637/77,949 (9.8%) | |||||
| Any iodine supplement use GW 0–20 | 28,998 | 1.01 (0.96, 1.06) | 0.83 | 0.91 (0.87, 0.96) | < 0.001 | 0.95 (0.88, 1.02) |
| First report of iodine supplement | ||||||
| Never (non-supplement user) | 48,951 (13,393b) | 1 (ref.) | 1 (ref.) | 1 (ref.) | ||
| Before pregnancyc | 7439 | 0.97 (0.89, 1.06) | 0.49 | 0.89 (0.82, 0.97) | 0.009 | 0.91 (0.82, 1.01) |
| GW 0–12 | 7121 | 0.98 (0.90, 1.07) | 0.70 | 0.88 (0.80, 0.95) | 0.003 | 0.91 (0.82, 1.02) |
| GW > 12 | 5229 | 1.04 (0.94, 1.14) | 0.44 | 0.93 (0.84, 1.02) | 0.139 | 0.95 (0.85, 1.07) |
| LGA | 7539/77,949 (9.7%) | |||||
| Any iodine supplement use GW 0–20 | 28,998 | 0.92 (0.88, 0.97) | 0.002 | 1.03 (0.98, 1.08) | 0.31 | 1.02 (0.95, 1.10) |
| First report of iodine supplement | ||||||
| Never (non-supplement user) | 48,951 (13,393b) | 1 (ref.) | 1 (ref.) | 1 (ref.) | ||
| Before pregnancyc | 7439 | 1.00 (0.92, 1.08) | 0.92 | 1.10 (1.01, 1.19) | 0.034 | 1.08 (0.97, 1.19) |
| GW 0–12 | 7121 | 0.89 (0.82, 0.97) | 0.011 | 1.03 (0.94, 1.12) | 0.57 | 1.02 (0.92, 1.14) |
| GW > 12 | 5229 | 0.88 (0.80, 0.97) | 0.014 | 1.01 (0.91, 1.12) | 0.89 | 1.01 (0.90, 1.14) |
aModels were adjusted for maternal age, BMI, parity, education, smoking in pregnancy, fibre intake, chronic illness, in vitro fertilization, folic acid supplement within the interval from 4 weeks before to 8 weeks after conception (only for intrauterine death), child sex (only for unstandardized birth weight), and vitamin D (only for preeclampsia)
bAdjusted associations restricting the reference group (non-users) to participants who reported use of one or more multivitamin/multimineral supplements in the food frequency questionnaire, but not any containing iodine
cOne to 26 weeks before conception