Table 1. Association between maternal and newborn co-factors and microcephaly.
The total number and prevalence of cases in the final case-control dataset, stratified by categories of neonatal and maternal variables, are shown. Data from the scanned and LMP cohorts are pooled in these analyses, but cohort-specific frequencies are shown in Table 3. Crude odds ratios (OR), 95% confidence intervals (CI) and P values from univariable logistic regression models estimating associations with microcephaly with each variable in turn are shown. The reference population in each of the models is assigned a value of 1. The total number of newborns included in each analysis varies due to missing data for some variables. *Systolic or diastolic blood pressure >140 or >90 mmHg, respectively.
| Covariate | Categories | n/N cases (%) | Crude OR (95% CI) | P value |
|---|---|---|---|---|
| Newborn factors | ||||
| Sex | Male | 69/4794 (1.4%) | 1 | |
| Female | 42/4303 (1.0%) | 0.67 (0.46, 0.99) | 0.05 | |
| Small for gestational age (SGA) | Normal | 61/7331 (0.8%) | 1 | |
| SGA | 50/1766 (2.8%) | 3.47 (2.38, 5.07) | <0.001 | |
| Type of birth | Singleton | 106/8879 (1.2%) | 1 | |
| Multifetal | 5/218 (2.3%) | 1.9 (0.80, 4.75) | 0.14 | |
| Year of birth | 2012 | 17/1381 (1.2%) | 1 | |
| 2013 | 28/1499 (1.9%) | 1.53 (0.83, 2.80) | 0.17 | |
| 2014 | 23/2379 (1.0%) | 0.78 (0.42, 1.47) | 0.45 | |
| 2015 | 23/2043 (1.1%) | 0.91 (0.49, 1.72) | 0.78 | |
| 2016 | 20/1795 (1.1%) | 0.90 (0.47, 1.73) | 0.76 | |
| Season | January – March | 24/2245 (1.1%) | 1 | |
| April – June | 41/2742 (1.5%) | 1.40 (0.85, 2.33) | 0.19 | |
| July – September | 22/2240 (1.0%) | 0.92 (0.51, 1.64) | 0.77 | |
| October – December | 24/1870 (1.3%) | 1.20 (0.68, 2.13) | 0.52 | |
| Maternal factors | ||||
| Sociodemographic factors | ||||
| Maternal age | <20 years | 17/1339 (1.3%) | 1 | |
| 20 to 35 years | 87/6966 (1.2%) | 0.98 (0.58, 1.66) | 0.95 | |
| >35 years | 7/783 (0.9%) | 0.70 (0.29, 1.70) | 0.43 | |
| Marital status | Married | 99/8329 (1.2%) | 1 | |
| Unmarried | 10/665 (1.5%) | 1.27 (0.66, 2.44) | 0.47 | |
| Education level | Secondary or more | 21/2627 (0.8%) | 1 | |
| Primary school | 73/5253 (1.4%) | 1.75 (1.07, 2.85) | 0.02 | |
| None | 13/1010 (1.3) | 1.62 (0.81, 3.24) | 0.17 | |
| Residence | Other | 70/5893 (1.2%) | 1 | |
| Kilifi township | 41/3176 (1.3%) | 1.09 (0.74, 1.60) | 0.67 | |
| Type of house | Stone wall | 45/4702 (1.0%) | 1 | |
| Mud wall | 63/4328 (1.5%) | 1.53 (1.04, 2.25) | 0.03 | |
| Obstetric history | ||||
| Parity | Primigravida | 41/3302 (1.2%) | 1 | |
| Multigravida | 70/5738 (1.2%) | 0.98 (0.67, 1.45) | 0.93 | |
| Antenatal care attendance | ≥4 visits | 69/5887 (1.2%) | 1 | |
| 0 to 3 visits | 42/3434 (1.3%) | 1.05 (0.72, 1.55) | 0.79 | |
| Medication during pregnancy | ||||
| Folic acid supplements | Yes | 102/8292 (1.2%) | 1 | |
| No | 9/795 (1.1%) | 0.92 (0.46, 1.82) | 0.81 | |
| Malaria prophylaxis | ≥3 doses | 61/5166 (1.2%) | 1 | |
| 1 to 2 doses | 47/3070 (1.5%) | 1.30 (0.89, 1.91) | 0.18 | |
| None | 3/689 (0.4%) | 0.37 (0.11, 1.17) | 0.09 | |
| Tetanus vaccination | Yes | 95/7706 (1.2%) | 1 | |
| No | 13/1137 (1.1%) | 0.93 (0.52, 1.66) | 0.80 | |
| Maternal co-morbidities and infections | ||||
| Mid-upper arm circumference
(MUAC) |
Normal (23–30cm) | 76/6490 (1.2%) | 1 | |
| Low (<23cm) | 13/990 (1.3%) | 1.12 (0.62, 2.03) | 0.70 | |
| High (≥30cm) | 9/997 (0.9%) | 0.77 (0.38, 1.54) | 0.46 | |
| Hypertension in pregnancy * | No | 92/7623(1.2%) | 1 | |
| Yes | 9/540 (1.7%) | 1.39 (0.70, 2.77) | 0.35 | |
| HIV status | Negative | 107/8605 (1.2%) | 1 | |
| Positive | 5/365 (1.1%) | 0.88 (0.32, 2.40) | 0.80 | |
| Maternal anaemia | No | 21/2321 (0.9%) | 1 | |
| Yes | 66/5436 (1.2%) | 1.35 (0.82, 2.20) | 0.24 | |
| VDRL (syphilis test) | Negative | 95/8014 (1.2%) | 1 | |
| Positive | 1/45 (2.2%) | 1.89 (0.26, 13.89) | 0.53 | |
| Other risk exposures | ||||
| Substance use | No | 108/8855 (1.2%) | 1 | |
| Yes | 3/232 (1.3%) | 1.06 (0.33, 3.37) | 0.92 | |
| Contact with cattle | No | 101/8225 (1.2%) | 1 | |
| Yes | 7/463 (1.5%) | 1.23 (0.57, 2.67) | 0.59 | |