Table 4.
Relative risks and 95% confidence intervals comparing women with each risk factor with women without the risk factor: maternal age and primiparity
| Age 15–19 years |
Age 35–45 years |
Primiparity |
||||
|---|---|---|---|---|---|---|
| Outcome | N | Pooled RR(95% CI) | N | Pooled RR (95% CI) | N | Pooled RR (95% CI) |
| COVID-19 severity and mortality | ||||||
| ICU admission | 12 | 1.42 (0.53–3.77) | 16 | 1.60 (1.36–1.89) | 14 | 0.90 (0.71–1.13) |
| Ventilation | 12 | 2.59 (0.79–8.51) | 16 | 2.13 (1.68–2.71) | 12 | 0.67 (0.39–1.16) |
| Critical care | 11 | 1.24 (0.48–3.17) | 15 | 1.62 (1.38–1.90) | 12 | 0.82 (0.62–1.08) |
| Pneumonia | 9 | 0.82 (0.62–1.08) | 10 | 1.51 (1.35–1.70) | 8 | 0.59 (0.46–0.77) |
| Pregnancy-related death | 13 | 0.73 (0.27–1.94) | 16 | 1.62 (0.81–3.24) | 14 | 0.75 (0.45–1.25) |
| Maternal morbidity | ||||||
| Hemorrhage | 6 | 1.93 (0.94–3.98) | 6 | 1.17 (0.82–1.68) | 7 | 1.26 (0.90–1.77) |
| Placental abruption | 5 | -- | 6 | 3.94 (1.40–11.13) | 6 | 0.64 (0.19–2.09) |
| Preeclampsia | 10 | 2.03 (0.89–4.61) | 13 | 1.12 (0.73–1.74) | 11 | 2.10 (1.45–3.03) |
| Preeclampsia or eclampsia | 8 | 3.27 (1.11–9.64) | 9 | 0.93 (0.63–1.37) | 8 | 1.75 (1.22–2.53) |
| Hypertensive disorders of pregnancy (any) | 10 | 2.06 (0.77–5.55) | 12 | 1.17 (0.93–1.49) | 10 | 1.56 (1.13–2.15) |
| Hypertensive disorders of pregnancy (at/after COVID-19) | 2 | -- | 3 | 1.91 (0.45–8.16) | 3 | 1.39 (0.54–3.57) |
| Preterm labor | 8 | 2.48 (0.53–11.60) | 10 | 1.39 (0.96–2.02) | 8 | 0.86 (0.51–1.43) |
| Preterm labor with onset before 37 wk GAa | 5 | 1.62 (0.42–6.22) | 8 | 1.28 (0.87–1.87) | 6 | 0.88 (0.51–1.51) |
| Cesarean delivery | 10 | 0.86 (0.65–1.13) | 13 | 1.21 (1.10–1.32) | 12 | 1.00 (0.90–1.11) |
| Intrapartum cesarean delivery | 9 | 0.90 (0.63–1.31) | 10 | 1.03 (0.89–1.20) | 8 | 1.35 (1.14–1.60) |
| Fetal and neonatal mortality and morbidity | ||||||
| Stillbirthb | 15 | 4.59 (1.69–12.45) | 18 | 1.75 (0.92–3.33) | 17 | 1.34 (0.62–2.90) |
| Perinatal death | 11 | 4.80 (1.28–17.99) | 14 | 1.53 (0.82–2.83) | 12 | 1.78 (0.89–3.54) |
| Early neonatal death | 11 | 5.94 (1.02–34.56) | 14 | 1.80 (0.51–6.33) | 12 | 1.60 (0.45–5.62) |
| Neonatal deathc | 12 | 9.38 (2.21–39.89) | 15 | 1.96 (0.65–5.87) | 13 | 1.25 (0.43–3.60) |
| NICU admission at birth | 6 | 1.59 (0.48–5.23) | 9 | 1.35 (1.12–1.63) | 8 | 1.03 (0.85–1.25) |
| Adverse birth outcomes | ||||||
| Very low birthweight (<1500 g) | 13 | 6.27 (1.86–21.15) | 16 | 1.39 (0.89–2.16) | 14 | 1.03 (0.61–1.73) |
| Low birthweight (<2500 g) | 13 | 0.96 (0.54–1.73) | 16 | 1.24 (1.04–1.47) | 14 | 1.27 (1.04–1.54) |
| Small for gestational age (3rd) | 14 | 4.33 (1.87–10.06) | 17 | 1.46 (1.01–2.12) | 15 | 2.11 (1.42–3.11) |
| Small for gestational age (10th) | 14 | 1.40 (0.83–2.36) | 17 | 0.98 (0.79–1.21) | 15 | 1.74 (1.41–2.15) |
| Moderate preterm birth (<34 wk) | 14 | 3.06 (1.48–6.35) | 17 | 1.51 (1.19–1.93) | 15 | 1.10 (0.84–1.44) |
| Moderate preterm birth (<34 wk) with onset before 34 wk GAa | 7 | 2.90 (1.18–7.14) | 10 | 1.43 (1.07–1.90) | 8 | 1.07 (0.74–1.53) |
| Preterm birth (<37 wk) | 14 | 1.22 (0.84–1.78) | 18 | 1.40 (1.19–1.64) | 15 | 1.02 (0.87–1.19) |
| Preterm birth (<37 wk) with onset before 37 wk GAa | 7 | 1.06 (0.68–1.67) | 11 | 1.27 (1.07–1.50) | 9 | 1.02 (0.83–1.26) |
Relative risks are calculated by pooling unadjusted relative risks from all participating studies with at least 1 adverse event for the given outcome using a DerSimonian–Laird random-effects model meta-analysis. For any study with 0 events in one arm (Risk Group or Reference Group), we used a continuity correction of the inverse of the number of events in the oppposite group within the same study.
CI, confidence interval; GA, gestational age; ICU, intensive care unit; NICU, neonatal intensive care unit; RR, relative risk.
Smith. Individual patient data meta-analysis: risk factors among COVID-19 pregnancies. Am J Obstet Gynecol 2023.
These outcomes (preterm labor, moderate preterm birth before 34 weeks’ gestation, and preterm birth before 37 weeks’ gestation) were included in the sensitivity analyses where we restricted confirmed COVID-19 cases to those with confirmed COVID-19 onset before 37 weeks’ gestation (or 34 weeks for very moderate preterm birth). The full comparison group was used for each of the sensitivity analyses
The outcome presented here is stillbirths occurring at ≥28 weeks’ gestation per the World Health Organization definition
The outcome “neonatal death” was reported by 15 participating studies. However, most studies were not designed to follow up neonates until 28 days after birth. Therefore, counts of neonatal death are underestimated.