Table 1a. Maternal characteristics and umbilical artery acidosis, birth asphyxia-related complications and admission to NICU.

	Acidosisa				Birth asphyxia-related complicationsb		Admission to NICU
Maternal characteristics	N totalc	N	%	N total	N	%	N	%
	33 429	360	1.08	42 539	269	0.63	2733	6.42
Age (years)
<25	5980	56	0.94	7721	33	0.43	403	5.22
25–29	11 026	117	1.06	14 102	78	0.55	898	6.37
30–34	11 557	118	1.02	14 571	102	0.70	936	6.42
⩾35	4866	69	1.42	6145	56	0.91	496	8.07
Height (cm)
⩽154	880	11	1.25	1162	14	1.20	93	8.00
155–164	11 201	146	1.30	14 331	103	0.72	1002	6.99
165–174	17 139	171	1.00	21 739	129	0.59	1 331	6.12
⩾175	3880	24	0.62	4890	19	0.39	279	5.71
Missing	329			417
BMI (kg m−2)
<18.5	1113	9	0.81	1 450	5	0.34	66	4.55
18.5–24.9	22 789	230	1.01	28 950	181	0.63	1746	6.03
25–29.9	6077	72	1.18	7758	54	0.70	572	7.37
⩾30	2126	30	1.41	2681	23	0.86	235	8.77
Missing	1324			1700
Daily smoking
Non-smoker	31 581	349	1.11	40 198	259	0.64	2613	6.50
Smoker	1807	9	0.50	2287	9	0.39	114	4.98
Missing	41			54
Hypertensive disease
No	31 370	334	1.06	39 976	249	0.62	2 516	6.29
Pre-gest hypertension	181	2	1.10	234	0	0	17	7.26
Gestational hypertension	737	10	1.36	916	6	0.66	76	8.30
Preeclampsia	1141	14	1.23	1 413	14	0.99	124	8.78
Diabetes
No	33 166	348	1.05	42 215	263	0.62	2666	6.32
Pre-gestational	118	6	5.08	147	4	2.72	36	24.49
Gestational	145	6	4.14	177	2	1.13	31	17.51

Abbreviations: BE, base excess; BMI, body mass index; HIE, hypoxic ischemic encephalopathy; MAS, meconium aspiration syndrome; NICU, neonatal intensive care unit.

Nulliparous women with singleton births, in cephalic presentation at ⩾37 gestational weeks in the Stockholm-Gotland Obstetric Cohort, Sweden 2008–2013.

^aAcidosis: umbilical artery acidosis, pH <7.05 and BE< −12.

^bBirth asphyxia-related complications include any of the following conditions: HIE, hypothermia treatment, neonatal seizures, MAS or advanced resuscitation after birth (heart compressions or intubation).

^cMissing data on pH and/or BE: N=9110.