Table 2.
Associations of exposure to the COVID-19 lockdown with gestational length
| No. of participants | Gestational length (week, Mean ± SD) | Mean difference in gestational length (week) | ||||
| Unexposed group | Exposed group b | Unexposed group | Exposed group b | Crude β (95% CI) | Adjusted β (95% CI) * | |
| Gestational week at the beginning of the Level I lockdown | ||||||
| All | 493,496 | 101,900 | 38.74 ± 1.46 | 38.66 ± 1.46 | −0.08 (−0.09, −0.07) | −0.06 (−0.07, −0.05) |
| Conception during the lockdown | 64,645 | 11,317 | 38.72 ± 1.52 | 38.64 ± 1.49 | −0.08 (− 0.11, − 0.05) | −0.04 (− 0.07, − 0.01) |
| Prior to 4th | 53,300 | 10,937 | 38.71 ± 1.50 | 38.64 ± 1.50 | −0.07 (− 0.10, − 0.04) | − 0.10 (− 0.14, − 0.07) |
| 4th -7th | 50,973 | 10,494 | 38.67 ± 1.52 | 38.52 ± 1.54 | − 0.14 (− 0.17, − 0.11) | − 0.13 (− 0.16, − 0.09) |
| 8th -11th | 48,926 | 10,237 | 38.70 ± 1.50 | 38.58 ± 1.54 | −0.12 (− 0.15, − 0.08) | −0.10 (− 0.13, − 0.07) |
| 12th -15th | 46,255 | 9844 | 38.73 ± 1.51 | 38.61 ± 1.55 | −0.11 (− 0.15, − 0.08) | −0.11 (− 0.14, − 0.07) |
| 16th -19th | 45,913 | 9539 | 38.74 ± 1.48 | 38.63 ± 1.52 | −0.11 (− 0.14, − 0.08) | −0.10 (− 0.13, − 0.06) |
| 20th -23rd | 41,017 | 8830 | 38.74 ± 1.49 | 38.64 ± 1.52 | −0.10 (− 0.14, − 0.07) | −0.10 (− 0.13, − 0.06) |
| 24th -27th | 40,358 | 8750 | 38.68 ± 1.49 | 38.66 ± 1.44 | −0.02 (− 0.06, 0.01) | −0.01 (− 0.04, 0.03) |
| 28th -31st | 38,146 | 8101 | 38.72 ± 1.39 | 38.63 ± 1.36 | −0.09 (− 0.12, − 0.06) | −0.07 (− 0.10, − 0.04) |
| 32nd -36th | 47,382 | 10,213 | 38.74 ± 1.21 | 38.73 ± 1.18 | −0.01 (− 0.03, 0.02) | 0.02 (− 0.01, 0.04) |
| 37th - 41st | 16,581 | 3638 | 39.40 ± 0.92 | 39.41 ± 0.93 | 0.01 (−0.02, 0.04) | 0.03 (0.01, 0.07) |
| Exposure dose (Mean ± SD) | Gestational length (week, Mean ± SD) | Mean difference in gestational length (week) | ||||
| Unexposed group | Exposed group | Unexposed group | Exposed group | Crude β (95% CI) | Adjusted β (95% CI) * | |
| Cumulative exposure dose in the first 22 weeks during the Level I to the Level III lockdown a | ||||||
| Per 100 unit increase in all participants | 0 ± 0 | 195.08 ± 82.21 | 38.74 ± 1.45 | 38.61 ± 1.52 | −0.06 (−0.07, −0.05) | −0.05 (− 0.06, − 0.04) |
| Categories of cumulative exposure dose | ||||||
| Unexposed group | 0 ± 0 | – | 38.74 ± 1.45 | – | Reference | Reference |
| Q1 (< 132) | – | 73.40 ± 38.11 | – | 38.64 ± 1.52 | −0.10 (− 0.13, − 0.08) | −0.09 (− 0.11, − 0.07) |
| Q2 (132–225) | – | 178.66 ± 27.17 | – | 38.59 ± 1.54 | −0.15 (− 0.17, − 0.12) | −0.13 (− 0.16, − 0.11) |
| Q3 (226–263) | – | 247.18 ± 10.58 | – | 38.58 ± 1.51 | −0.16 (− 0.18, − 0.13) | −0.14 (− 0.16, − 0.11) |
| Q4 (≥264) | – | 278.80 ± 8.59 | – | 38.62 ± 1.51 | − 0.12 (− 0.14, − 0.10)* | −0.09 (− 0.11, − 0.07) |
| P for trend test | < 0.001 | |||||
In calculating the cumulative exposure dose to lockdown, we assigned a weighting of 3 to days with Level I response, 2 to days with Level II response, 1 to days with Level III response, and 0 to other days
* Adjusted for maternal age, marital status, parity, residential city, delivery type and infant sex
a The exposed group refers to the pregnant women who have experienced the COVID-19 lockdown in their first 22 GWs. The other participants were defined as the unexposed group. The individual cumulative exposure dose was calculated by combining the weightings with the overlap between their pregnancy period ≤22 GWs and the three levels of responses. Q1-Q4 were defined as the cumulative exposure dose of the exposed group classified by quartiles, and the unexposed group was used as reference
b Pregnant women who have experienced the COVID-19 lockdown (from 1/23/2020 to 2/24/2020) during any period of their pregnancy were defined as the exposed group. We further divided the exposed group into subgroups according to their gestational weeks (GW) on 1/23/2020, the beginning of lockdown
-: Not applicable