Table 4.

Outcomes by parity

	Nulliparous n=18,245	Multiparous n=21,625	aRR (95%CI)*
Composite of neonatal adverse outcomes†	274 (1.5)	215 (1.0)	1.80 (1.48–2.19)
Perinatal death	4 (0.0)	4 (0.0)
Ventilator support or cardiopulmonary resuscitation	101 (0.6)	39 (0.2)
Apgar score <5 at 5 min	60 (0.3)	23 (0.1)
Hypoxic-ischemic encephalopathy	39 (0.2)	17 (0.1)
Seizure	26 (0.1)	8 (0.0)
Sepsis—confirmed	21 (0.1)	12 (0.1)
Bronchopulmonary dysplasia	2 (0.0)	1 (0.0)
Persistent pulmonary hypertension of the newborn	24 (0.1)	14 (0.1)
Necrotizing enterocolitis, stage 2 or 3	1 (0.0)	0 (0.0)
Intraventricular hemorrhage, grade III or IV	1 (0.0)	0 (0.0)
Intracranial hemorrhage other than intraventricular hemorrhage	29 (0.2)	21 (0.1)
Fracture—any	47 (0.3)	110 (0.5)
Brachial plexus palsy	21 (0.1)	14 (0.1)
Facial nerve palsy	4 (0.0)	1 (0.0)
Composite of maternal adverse outcomes	2,756 (15.1)	718 (3.3)	5.04 (4.62–5.49)
Endometritis	155 (0.9)	60 (0.3)
Antibiotics for chorioamnionitis	1,496 (8.2)	287 (1.3)
Wound infection	29 (0.2)	13 (0.1)
3rd or 4th degree perineal laceration	1,090 (6.0)	247 (1.1)
Blood transfusion	191 (1.0)	136 (0.6)
Thromboembolism	0 (0.0)	1 (0.0)
Intensive care unit admission	20 (0.1)	31 (0.1)
Death	0 (0.0)	0 (0.0)
Shoulder dystocia requiring maneuvers	402 (2.2)	692 (3.2)	0.68 (0.60–0.77)
Size for gestational age			aOR (95%CI)*
Small	1,617 (8.9)	1,252 (5.8)	1.45 (1.33–1.57)
Large	1,105 (6.1)	2,261 (10.5)	0.65 (0.60–0.71)

Data are n (%) unless otherwise noted.

aRR, adjusted relative risk from modified Poisson regression; CI, confidence interval; aOR, adjusted odds ratio from multinomial logistic regression.

^*Adjusted for age, race/ethnicity, body mass index at delivery, and insurance. All associations were p<0.001.

^†Missing in 53