Table 2.

Predicted absolute risks (95% confidence intervals) of adverse pregnancy and birth outcomes at specified values of maternal age among nulliparous women in British Columbia (Canada), 2004–2014 (n=203,414).

	20 years	25 years	30 years	35 years	40 years	45 years	50 years

Gestational diabetes mellitus^a n=15,375 (7.6%)

Unadjusted	2.1 (1.9, 2.2)	5.0 (4.9, 5.2)	8.0 (7.8, 8.2)	11 (11, 11)	15 (15, 16)	21 (20, 23)	29 (26, 31)
Adjusted	3.6 (3.2, 4.1)	7.9 (7.1, 8.8)	12 (11, 13)	15 (14, 17)	20 (18, 22)	25 (23, 28)	32 (28, 36)

Hypertensive disorders of pregnancy n=15,708 (7.7%)

Unadjusted	6.5 (6.2, 6.8)	7.3 (7.1, 7.5)	7.2 (7.0, 7.4)	8.4 (8.2, 8.6)	12 (11, 12)	17 (16, 18)	24 (21, 26)
Adjusted	5.1 (4.5, 5.8)	5.4 (4.8, 6.1)	5.4 (4.8, 6.1)	6.3 (5.5, 7.1)	8.6 (7.5, 9.7)	12 (10, 14)	16 (14, 19)

Cesarean delivery n=68,050 (33.5%)

Unadjusted	21 (20, 21)	28 (28, 28)	33 (33, 33)	41 (41, 42)	54 (54, 55)	68 (66, 69)	78 (77, 80)
Adjusted	21 (20, 22)	28 (27, 29)	33 (32, 35)	41 (39, 42)	51 (50, 54)	64 (62, 66)	74 (72, 76)

Preterm delivery n= 20,028 (9.9%)

Unadjusted	8.8 (8.5, 9.2)	8.5 (8.3, 8.7)	9.1 (8.9, 9.2)	12 (11, 12)	15 (15, 16)	20 (19, 21)	25 (24, 27)
Adjusted	6.3 (5.6, 7.1)	6.4 (5.7, 7.1)	6.8 (6.1, 7.5)	7.8 (7.0, 8.7)	9.3 (8.3, 10)	11 (10, 12)	13 (11, 15)

Spontaneous preterm delivery n=10,667 (5.2%)

Unadjusted	5.9 (5.6, 6.1)	4.9 (4.7, 5.0)	5.0 (4.9, 5.1)	5.5 (5.3, 5.7)	5.7 (5.4, 6.1)	6.0 (5.3, 6.8)	6.2 (5.2, 7.5)
Adjusted	3.6 (3.1, 4.2)	3.3 (2.8, 3.8)	3.5 (3.0, 4.0)	3.6 (3.1, 4.1)	3.4 (2.9, 4.0)	3.2 (2.5, 3.9)	3.0 (2.3, 3.8)

Indicated preterm delivery n=9,364 (5.4)

Unadjusted	3.1 (2.9, 3.3)	3.4 (3.3, 3.5)	4.2 (4.0, 4.3)	6.0 (5.9, 6.2)	9.2 (8.7, 9.6)	14 (13, 15)	20 (18, 22)
Adjusted	2.6 (2.2, 3.1)	2.9 (2.5, 3.4)	3.4 (2.9, 4.0)	4.4 (3.7, 5.1)	5.8 (4.9, 6.7)	7.6 (6.3, 9.0)	9.9 (8.1, 12)

Multiple gestations n=7,188 (3.5%)

Unadjusted	1.7 (1.5, 1.8)	2.1 (2.0, 2.2)	3.0 (2.9, 3.1)	5.2 (5.0, 5.4)	9.3 (8.8, 9.9)	16 (15, 18)	27 (24, 30)
Adjusted	0.95 (0.72, 1.2)	1.3 (1.0, 1.7)	1.4 (1.1, 1.7)	1.9 (1.5, 2.4)	2.6 (2.1, 3.4)	3.6 (2.8, 4.7)	5.0 (3.7, 6.5)

Major congenital anomaly n=6,735 (3.3)

Unadjusted	3.1 (2.9, 3.2)	3.1 (3.0, 3.1)	3.2 (3.1, 3.3)	3.6 (3.5, 3.8)	4.2 (4.0, 4.5)	4.9 (4.4, 5.4)	5.7 (4.9, 6.6)
Adjusted	2.7 (2.2, 3.2)	2.8 (2.3, 3.2)	2.9 (2.5, 3.4)	3.5 (3.0, 4.2)	3.9 (3.2, 4.8)	3.9 (3.1, 4.8)	4.4 (3.5, 5.5)

Small-for-gestational age^c n=18,816 (9.6)

Unadjusted	8.7 (8.4, 9.0)	9.3 (9.2, 9.5)	9.8 (9.6, 1)	10. (9.9, 10)	10 (10, 11)	11 (10, 11)	11 (10, 12)
Adjusted	8.5 (7.7, 9.4)	9.8 (8.8, 11)	11 (9.9, 12)	11 (10, 13)	12 (11, 13)	12 (11, 14)	13 (11, 14)

Neonatal intensive care unit stay 48 hours^b n=9,668 (7.7)

Unadjusted	6.0 (5.7, 6.3)	6.4 (6.2, 6.6)	7.3 (7.1, 7.5)	9.3 (9.0, 9.5)	12 (12, 13)	16 (14, 17)	20 (18, 22)
Adjusted	2.8 (2.4, 3.3)	3.2 (2.7, 3.7)	3.6 (3.1, 4.2)	4.3 (3.7, 5.0)	5.1 (4.4, 6.0)	6.2 (5.2, 7.3)	7.4 (6.1, 9.0)

Stillbirth n=2,064 (1.0)

Unadjusted	1.6 (1.5, 1.8)	0.94 (0.86, 1.0)	0.81 (0.74, 0.88)	0.88 (0.81, 0.97)	1.4 (1.2, 1.5)	2.1 (1.7, 2.7)	3.3 (2.3, 4.8)
Adjusted	0.90 (0.66, 1.2)	0.61 (0.44, 0.84)	0.52 (0.38, 0.71)	0.54 (0.40, 0.75)	0.73 (0.52, 1.0)	1.0 (0.66, 1.5)	1.36 (0.81, 2.3)

Neonatal mortality n=467 (0.2)

Unadjusted	0.26 (0.21, 0.33)	0.24 (0.20, 0.29)	0.20 (0.17, 0.24)	0.21 (0.17, 0.26)	0.31 (0.24, 0.41)	0.47 (0.26, 0.84)	0.72 (0.29, 1.79)
Adjusted	0.11 (0.05, 0.22)	0.11 (0.06, 0.23)	0.10 (0.05, 0.20)	0.09 (0.04, 0.19)	0.11 (0.05, 0.24)	0.14 (0.05, 0.34)	0.17 (0.05, 0.54)

Infant mortality n=662 (0.3)

Unadjusted	0.50 (0.43, 0.57)	0.32 (0.27, 0.37)	0.26 (0.23, 0.31)	0.28 (0.23, 0.33)	0.42 (0.33, 0.53)	0.65 (0.40, 1.1)	1.0 (0.46, 2.2)
Adjusted	0.19 (0.10, 0.37)	0.15 (0.08, 0.28)	0.13 (0.07, 0.25)	0.13 (0.07, 0.24)	0.16 (0.08, 0.31)	0.21 (0.09, 0.46)	0.27 (0.10, 0.74)

Maternal mortality or severe near-miss morbidity n=1,221 (0.6)

Unadjusted	0.47 (0.40, 0.55)	0.40 (0.34, 0.46)	0.49 (0.43, 0.55)	0.78 (0.70, 0.86)	1.5 (1.3, 1.6)	2.7 (2.1, 3.5)	5.1 (3.4, 7.4)
Adjusted	0.35 (0.22, 0.54)	0.30 (0.19, 0.47)	0.37 (0.24, 0.57)	0.58 (0.37, 0.89)	1.0 (0.64, 1.54)	1.7 (1.1, 2.8)	3.0 (1.7, 5.2)

Adverse fetal-infant composite outcome n=10,167 (5.0)

Unadjusted	5.4 (5.2, 5.6)	4.6 (4.5, 4.7)	4.5 (4.4, 4.6)	5.4 (5.2, 5.5)	6.8 (6.5, 7.2)	8.7 (8.0, 9.4)	11 (9.8, 12)
Adjusted	4.0 (3.5, 4.7)	3.7 (3.2, 4.2)	3.6 (3.2, 4.2)	4.1 (3.6, 4.7)	4.8 (4.1, 5.6)	5.7 (4.8, 6.7)	6.6 (5.5, 8.0)

Composite healthy pregnancy and birth outcome n=103,881 (51.1)

Unadjusted	77 (77, 78)	76 (76, 76)	74 (73, 74)	68 (68, 68)	59 (59, 60)	50 (49, 51)	41 (39, 43)
Adjusted	79 (77, 80)	77 (75, 78)	74 (73, 76)	70 (68, 71)	64 (62, 66)	57 (55, 59)	50 (47, 53)

Maternal age at first birth was modeled using restricted cubic splines with 4 knots (at the 5th, 35th, 65th, and 95th percentiles; ages 19.7, 27.1, 31.5, and 38.6) for gestational diabetes, hypertensive disorders of pregnancy, cesarean delivery, spontaneous preterm delivery, and healthy preterm delivery and modeled using restricted cubic splines with 3 knots (at the 10th, 50th, and 90th percentiles; ages 21.4, 29.3, and 36.5) for all other outcomes.

Adjusted models included pre-pregnancy diabetes, pre-pregnancy chronic hypertension, pre-pregnancy body mass index, smoking, indicator variables for calendar year, inadequate prenatal care (yes/no, defined as <5 visits), low income (defined by <3^rd decile postal code), rural residence (defined by community size <10,000), previous spontaneous or therapeutic abortion, diagnosed infertility (defined by ICD-9-CM code 628), infertility treatment.

Models for gestational diabetes were restricted to those without pre-pregnancy type 1 or type 2 diabetes mellitus.

Models for neonatal intensive care unit (NICU) stay ≥48 hours restricted to births after April 1, 2008, when coding criteria changed.

Models for small-for-gestational age restricted to singleton pregnancies and gestational ages between 22 and 43 weeks, in accordance with reference charts