Characteristics of microcephaly cases
| All registries excluding Brazil* | Brazil | ||||||
| Pre Zika | Zika |
P value | Pre Zika | Zika |
P value | ||
| 2010–2015† | 2016–2017‡ | 2010–2014 | 2015–2017 | ||||
| n (%) | n (%) | n (%) | n (%) | ||||
| All cases | 543 (100) | 687 (100) | 852 (100) | 4588 (100) | |||
| Birth outcome§ | Live birth | 523 (97) | 661 (97) | 0.72 | 852 (100) | 4588 (100) | |
| Stillbirth | 17 (3) | 19 (3) | 0 | 0 | |||
| Sex | Male | 226 (42) | 299 (44) | 0.73¶ | 371 (45) | 1853 (41) | 0.04 |
| Female | 307 (57) | 374 (55) | 461 (55) | 2702 (59) | |||
| Indeterminate | 8 (1) | 12 (2) | 0 | 0 | |||
| Twin | Yes | 19 (5) | 13 (2) | 0.009 | 29 (3) | 85 (2) | 0.017 |
| Prenatally diagnosed | Yes | 77 (19) | 91 (17) | 0.38 | No information | ||
| Pre-term | <37 weeks | 179 (33) | 190 (28) | 0.032 | 213 (25) | 870 (19) | <0.001 |
| Term not specified | 17 (3) | 15 (2) | 235 (28) | 99 (2) | |||
| Birth weight | <2500 g | 286 (54) | 356 (59) | 0.045 | 447 (52) | 1881 (41) | <0.001 |
| Birth weight z-score | No information | 25 (5) | 92 (13) | <0.001 | 237 (28) | 103 (2) | <0.001 |
| <−3SD | 31/518 (6) | 31/595 (5) | <0.001 | 53/615 (9) | 167/4485 (4) | <0.001 | |
| −3SD to <−2SD | 69/518 (13) | 111/595 (19) | 71/615 (12) | 597/4485 (13) | |||
| −2SD to <−1SD | 145/518 (28) | 207/595 (35) | 159/615 (26) | 1422/4485 (32) | |||
| ≥−1SD | 273/518 (53) | 246/595 (41) | 332/615 (54) | 2299/4485 (51) | |||
| Head circumference z-score | No information | 364 (67) | 195 (28) | <0.001 | |||
| <−3SD | 45/179 (25) | 152/492 (31) | |||||
| −3SD to <−2SD | 66/179 (37) | 220/492 (45) | 0.01 | No information | |||
| −2 SD to <−1SD | 50/179 (28) | 89/492 (18) | |||||
| ≥−1SD | 18/179 (10) | 31/492 (6) | |||||
| Head circumference z score in pre-term births | <−3SD | 13/39 (33) | 50/134 (37) | ||||
| −3SD to <−2SD | 9/39 (23) | 57/134 (43) | 0.005 | No information | |||
| −2SD to <−1SD | 11/39 (28) | 11/134 (8) | |||||
| ≥−1SD | 6/39 (15) | 16/134 (12) | |||||
| Head circumference z score in term births | <−3SD | 32/140 (23) | 102/358 (28) | ||||
| −3SD to <−2SD | 57/140 (41) | 163/358 (46) | 0.08 | No information | |||
| −2SD to <−1SD | 39/140 (28) | 78/358 (22) | |||||
| ≥−1SD | 12/140 (9) | 15/358 (4) | |||||
*Mexico Nuevo Leon contributed data for 2015–2017 only, Chile National for 2016–2017 only and Colombia Bogota for 2014–2017 only.
†Total microcephaly cases, 543, for 2010–2015 excludes 11 cases from Nicaragua as case-level data not available.
‡Total microcephaly cases, 687, for 2016–2017 excludes 30 cases from Nicaragua and 78 cases from Argentina (2017) as case-level data not available.
§Birth outcome: n=661 live births in 2016–2017 includes 121 cases from Chile National who do not collect data on still births. p=0.82 for 2010–2015 versus 2016–2017 excluding these cases.
¶p=0.48 when the indeterminate sex is excluded.