Maternal age at delivery* | N, Unadjusted RR (95% CI) | |||
---|---|---|---|---|
Twins (any chorionicity) | Dichorionic twins | Monochorionic twins | Singletons* | |
<20 | N=14 RR=1.93 (0.96 to 3.88) | N=5 RR=1.06 (0.33 to 3.44) | N=8 RR=3.37 (1.27 to 8.95) | N=290 RR=0.94 (0.83 to 1.07) |
20–29 | N=66 RR=1 (reference) | N=40 RR=1 (reference) | N=21 RR=1 (reference) | N=1491 RR=1 (reference) |
30–34 | N=40 RR=0.74 (0.50 to 1.10) | N=25 RR=0.76 (0.46 to 1.26) | N=11 RR=0.64 (0.31 to 1.33) | N=754 RR=1.04 (0.95 to 1.13) |
≥35 | N=34 RR=0.97 (0.64 to 1.47) | N=26 RR=1.22 (0.75 to 2.01) | N=7 RR=0.63 (0.27 to 1.48) | N=422 RR=1.03 (0.93 to 1.15) |
Year of delivery | RR=1.00 (0.96 to 1.04) | RR=0.96 (0.91 to 1.02) | RR=1.08 (1.01 to 1.18) | RR=0.98 (0.97 to 0.99) |
*Twenty-nine (0.7%) singletons had missing maternal age data and were excluded. Maternal age data were missing in 2.1% of twins without CHD so these were excluded from the denominator.
CHD, congenital heart disease; RR, relative risk.