Table 4.

Association between maternal BMI and severe asphyxia-related outcomes using the conventional and fetuses-at-risk approaches: moderately preterm (32–36 weeks) singleton infants without congenital malformation in Sweden 1997–2011

Outcomes	Per 10 units of BMIa	Maternal BMI
		<25	25 to <30	30 to <35	≥35
Conventional approach b
Apgar score 0–3 at 5 minutes
Adjusted RR (95% CI)	1.37 (1.07–1.75)	1 [Reference]	1.18 (0.87–1.61)	1.50 (0.99–2.28)	2.01 (1.21–3.35)
Apgar score 0–3 at 10 minutesc
Adjusted RR (95% CI)	1.50 (1.11–2.02)	1 [Reference]	1.38 (0.94–2.03)	1.23 (0.68–2.21)	2.45 (1.32–4.53)
Neonatal seizures
Adjusted RR (95% CI)	1.46 (1.10–1.93)	1 [Reference]	0.87 (0.59–1.28)	1.20 (0.73–1.99)	2.08 (1.21–3.59)
IVH grades 1–4
Adjusted RR (95% CI)	0.91 (0.57–1.45)	1 [Reference]	0.71 (0.42–1.18)	0.52 (0.21–1.28)	1.73 (0.83–3.60)
Fetuses-at-risk approach d
Apgar score 0–3 at 5 minutes
Adjusted RR (95% CI)	1.50 (1.14–1.96)	1 [Reference]	1.20 (0.88–1.64)	1.68 (1.10–2.56)	2.59 (1.55–4.38)
Apgar score 0–3 at 10 minutesc
Adjusted RR (95% CI)	1.70 (1.23–2.37)	1 [Reference]	1.44 (0.98–2.11)	1.43 (0.79–2.60)	3.32 (1.76–6.24)
Neonatal seizures
Adjusted RR (95% CI)	1.69 (1.24–2.29)	1 [Reference]	0.91 (0.62–1.34)	1.43 (0.86–2.39)	2.87 (1.65–5.01)
IVH grades 1–4
Adjusted RR (95% CI)	0.97 (0.57–1.63)	1 [Reference]	0.72 (0.43–1.22)	0.59 (0.23–1.47)	2.21 (1.06–4.63)

BMI, body mass index; IVH, intraventricular haemorrhage; RR, risk ratio.

Model adjusted for maternal age at delivery, parity, smoking during pregnancy, height, education, country of birth and year of delivery.

^aTen units is the difference between the median BMIs of mothers with obesity (33.1) and without obesity (23.0).

^bIn the conventional approach, rate is calculated as the number of cases per 1000 births.

^cThirty-three infants had missing information on Apgar scores at 10 minutes.

^dIn the fetuses-at-risk approach, rate is calculated as the number of cases per 1000 live fetuses.