Table 3:

Association between age and timing of maternal prepregnancy surgery with risk of neonatal abstinence syndrome in infants^*

Maternal characteristics	No. of infants	No. of infants with neonatal abstinence syndrome	Prevalence per 10 000 (95% CI)	Risk ratio (95% CI)
Maternal characteristics	No. of infants	No. of infants with neonatal abstinence syndrome	Prevalence per 10 000 (95% CI)	Unadjusted	Adjusted^†
Two or more hospital admissions for surgery
Age at first surgery, yr
< 15	59 738	146	24.4 (20.5–28.4)	2.84 (2.38–3.39)	2.79 (2.32–3.37)
15–19	63 199	148	23.4 (19.6–27.2)	2.68 (2.25–3.20)	2.19 (1.83–2.64)
20–24	58 390	115	19.7 (16.1–23.3)	2.21 (1.80–2.71)	2.08 (1.69–2.56)
≥ 25	64 579	94	14.6 (11.6–17.5)	1.71 (1.38–2.12)	1.75 (1.40–2.19)
No surgery	1 476 399	1294	8.8 (8.3–9.2)	Referent	Referent
Age at last surgery, yr
< 15	16 939	34	20.1 (13.3–26.8)	2.30 (1.62–3.27)	2.10 (1.48–3.00)
15–19	34 196	82	24.0 (18.8–29.2)	2.62 (2.05–3.36)	1.98 (1.54–2.55)
20–24	62 777	132	21.0 (17.4–24.6)	2.40 (1.99–2.91)	2.06 (1.70–2.49)
≥ 25	131 994	255	19.3 (17.0–21.7)	2.24 (1.95–2.58)	2.39 (2.06–2.78)
No surgery	1 476 399	1294	8.8 (8.3–9.2)	Referent	Referent
Time between first surgery and future pregnancy, yr
< 5	57 376	89	15.5 (12.3–18.7)	1.76 (1.41–2.20)	1.50 (1.20–1.88)
5–9	72 284	142	19.6 (16.4–22.9)	2.25 (1.88–2.69)	1.99 (1.66–2.39)
≥ 10	116 247	272	23.4 (20.6–26.2)	2.70 (2.36–3.10)	2.87 (2.49–3.32)
No surgery	1 476 399	1294	8.8 (8.3–9.2)	Referent	Referent
Time between last surgery and future pregnancy, yr
< 5	160 270	336	21.0 (18.7–23.2)	2.39 (2.11–2.70)	2.18 (1.92–2.48)
5–9	52 995	110	20.8 (16.9–24.6)	2.38 (1.96–2.90)	2.29 (1.87–2.80)
≥ 10	32 641	57	17.5 (12.9–22.0)	2.03 (1.54–2.68)	2.17 (1.64–2.88)
No surgery	1 476 399	1294	8.8 (8.3–9.2)	Referent	Referent
One hospital admission for surgery
Age at surgery, yr
< 15	65 717	129	19.6 (16.2–23.0)	2.16 (1.78–2.62)	2.08 (1.71–2.54)
15–19	86 911	137	15.8 (13.1–18.4)	1.83 (1.53–2.20)	1.46 (1.21–1.76)
20–24	115 416	140	12.1 (10.1–14.1)	1.42 (1.18–1.70)	1.32 (1.10–1.58)
≥ 25	192 016	143	7.4 (6.2–8.7)	0.87 (0.72–1.04)	0.99 (0.82–1.20)
No surgery	1 476 399	1294	8.8 (8.3–9.2)	Referent	Referent
Time between surgery and future pregnancy, yr
< 5	239 777	250	10.4 (9.1–11.7)	1.20 (1.05–1.38)	1.14 (0.99–1.31)
5–9	107 903	130	12.0 (10.0–14.1)	1.36 (1.13–1.64)	1.34 (1.11–1.62)
≥ 10	112 380	169	15.0 (12.8–17.3)	1.71 (1.44–2.02)	1.95 (1.64–2.32)
No surgery	1 476 399	1294	8.8 (8.3–9.2)	Referent	Referent

Note: CI = confidence interval.
↵* Age and time were expressed in 5-year bounds, ensuring there were enough women in each category.
↵† Adjusted for maternal pain comorbidity, mental illness, age at delivery, parity, socioeconomic deprivation, place of residence and time period at birth.