Table 5. Zika-associated vs all adverse birth outcomes.

Exposure/Characteristic	CZS-specific adverse birth outcomes†		All adverse birth outcomes
	n (%)	RR (95% CI)	n (%)	RR (95% CI)
Lab Zika diagnosis
Naïve*	1 (1.3)		17 (22.1)
Unknown	1 (3.4)	1.3 (0.1, 20.8)	4 (13.8)	0.6 (0.2, 1.6)
Incident	1 (2.5)	1.0 (0.1, 15.2)	6 (15.0)	0.7 (0.3, 1.6)
Pre-Immune	0 (0.0)	0 (0, ∞)	5 (12.2)	0.5 (0.2, 1.3)
Clinical diagnosis of Zika
Yes	1 (11.1)	4.3 (0.4, 43.0)	3 (33.3)	2.0 (0.7, 5.6)
No*	2 (1.8)		30 (15.3)
LMP timing
Before 9/30/16	3 (2.7)	2.2 (0, ∞)	17 (15.2)	0.8 (0.4, 1.4)
After 9/30/16*	0 (0.0)		16 (19.5)
History of fever, rash, or malaise in pregnancy
Yes	2 (2.7)	1.6 (0.2, 17.7)	16 (21.6)	1.5 (0.8, 2.8)
No*	1 (0.8)		17 (14.2)
Prior pregnancy
Yes	1 (1.0)	0.3 (0.0, 3.5)	19 (19.2)	1.3 (0.7, 2.4)
No*	2 (2.1)		14 (14.7)
Prior preterm birth
Yes	0 (0.0)	0 (0, ∞)	6 (40.0)	2.7 (1.3, 5.4)
No*	3 (1.7)		27 (15.1)
Prior Caesarean delivery
Yes	0 (0.0)	0 (0, ∞)	6 (17.1)	1.0 (0.5, 2.3)
No*	3 (1.9)		27 (17.0)
Caesarean delivery this pregnancy
Yes	1 (15.4)	0.5 (0.0, 5.4)	12 (1.3)	0.8 (0.4, 1.6)
No*	2 (18.1)		21 (1.7)

* indicates the reference group for risk ratios

^† This group is defined by clinical exam findings of anomalies; one case was ZIKV+ by RT-PCR