Table 2:

Relative risk of a woman experiencing severe maternal morbidity or death between 20 weeks gestation and 42 days after the index birth, in relation to receipt of infertility treatment within the index pregnancy and relative to no infertility treatment

Stratification variable	Women who received infertility treatment*		Women who did not receive infertility treatment*		Relative risk (95% CI) of SMM or death
	No. with SMM or who died	No. at risk (rate per 1000)	No. with SMM or who died	No. at risk (rate per 1000)
Age < 40 yr	279	10 070 (27.7)	866	42 448 (20.4)	1.36 (1.19–1.55)
Age ≥ 40 yr	73	1443 (50.6)	155	5046 (30.7)	1.64 (1.25–2.16)
Singleton pregnancy	210	8933 (23.5)	798	40 693 (19.6)	1.20 (1.03–1.39)
Multiple pregnancy	135	2515 (53.7)	235	6696 (35.1)	1.52 (1.23–1.88)

Note: CI = confidence interval, SMM = severe maternal morbidity.

^*Number of pregnancies in propensity score–rematched cohorts were slightly lower than for the full model (total no. for age was 57 007: n = 11 513 with fertility treatment and n = 47 494 without fertility treatment; and total no. for singleton/multiple gestation was 58 837: n = 11 448 with fertility treatment and n = 47 389 without fertility treatment).