Table 4. Perinatal outcomes among twin live births by mode of conception.
| All | Birth weight | VLBW | LBW | VPTB | PTB | Postterm birth** | VSGA | SGA | LGA | 5′ Apgar <7* | Neonatal death | ||||||||||||
| N | Mean | Mean diff | N | OR | N | OR | N | OR | N | OR | N | OR | N | OR | N | OR | N | OR | N | OR | N | OR | |
| SD | 95% CI | % | 95%CI | % | 95%CI | % | 95%CI | % | 95%CI | % | 95%CI | % | 95%CI | % | 95%CI | % | 95%CI | % | 95%CI | % | 95%CI | ||
| Spontaneous | 7215 | 2426 | Ref | 575 | Ref | 3564 | Ref | 603 | Ref | 2859 | Ref | 4 | Ref | 193 | Ref | 683 | Ref | 703 | Ref | 226 | Ref | 142 | Ref |
| 613 | 8.0 | 49.4 | 8.4 | 39.6 | 0.1 | 2.7 | 9.5 | 9.7 | 3.1 | 2.0 | |||||||||||||
| Any assisted conception | 1609 | 2302 | −58 | 193 | 1.35 # | 907 | 1.12# | 200 | 1.32 # | 699 | 1.10# | 2 | 1.53 | 41 | 0.90 | 154 | 0.85# | 117 | 0.88 | 41 | 0.77 | 25 | 0.78# |
| 639 | −109,−8 | 12.0 | 1.05,1.72 | 56.4 | 0.96,1.30 | 12.4 | 1.02,1.71 | 43.4 | 0.93,1.30 | 0.1 | 0.15,15.9 | 2.6 | 0.64,1.27 | 9.6 | 0.69,1.04 | 7.3 | 0.70,1.12 | 2.6 | 0.51,1.16 | 1.6 | 0.45,1.35 | ||
| Spontaneous conception, fertile | 7016 | 2430 | Ref | 549 | Ref | 3457 | Ref | 578 | Ref | 2787 | Ref | 4 | Ref | 188 | Ref | 664 | Ref | 689 | Ref | 221 | Ref | 133 | Ref |
| 609 | 7.8 | 49.3 | 8.2 | 39.7 | 0.1 | 2.7 | 9.5 | 9.8 | 3.2 | 1.9 | |||||||||||||
| Spontaneous conception, IF DX*** | 166 | 2232 | −196 | 24 | 1.81 # | 96 | 1.23# | 23 | 1.62# | 65 | 0.90# | 0 | 1.85 | 5 | 0.99 | 17 | 0.93 | 11 | 0.57 | 5 | 0.88 | 9 | 2.86 |
| 730 | −354,−37 | 14.5 | 1.0003,3.29 | 57.8 | 0.83,1.81 | 13.9 | 0.86,3.05 | 39.2 | 0.58,1.41 | 0.0 | 0.17,20.1 | 3.0 | 0.41,2.37 | 10.2 | 0.51,1.72 | 6.6 | 0.22,1.44 | 3.0 | 0.31,2.53 | 5.4 | 1.11,7.39 | ||
| Spontaneous conception, IF TX**** | 33 | 2574 | −85 | 2 | 1.03 | 11 | 0.81 | 2 | 0.98 | 7 | 0.45 | 0 | 1.70 | 0 | 0.64 ∧ | 2 | 0.87 | 3 | 0.43 | 0 | 0.76∧ | 0 | 1.69∧ |
| 581 | −304,134 | 6.1 | 0.17,6.04 | 33.3 | 0.34,1.95 | 6.1 | 0.17,5.62 | 21.2 | 0.14,1.43 | 0.0 | 0.16,18.5 | 0.0 | 0.42,0.97 | 6.1 | 0.28,2.72 | 9.1 | 0.02,8.28 | 0.0 | 0.42,1.38 | 0.0 | 0.76,3.74 | ||
| Donor oocyte | 16 | 2271 | −104 | 2 | 1.42 | 10 | 1.41 | 4 | 2.90 | 8 | 1.18 | 0 | 1.54 | 0 | 0.35∧ | 1 | 0.35 | 1 | 0.72 | 0 | 1.32∧ | † | - |
| 682 | −575,368 | 12.5 | 0.16,12.9 | 62.5 | 0.32,6.20 | 25.0 | 0.55,15.4 | 50.0 | 0.27,5.14 | 0.0 | 0.12,19.0 | 0.0 | 0.05,2.45 | 6.3 | 0.04,2.78 | 6.3 | 0.14,3.71 | 0.0 | 0.31,5.67 | ||||
| GIFT | 212 | 2204 | −125 | 32 | 1.69# | 131 | 1.34# | 31 | 1.45# | 98 | 1.20 | 0 | 0.98 | 7 | 1.13 | 22 | 0.88# | 9 | 0.58 | 9 | 1.34 | 7 | 1.65 |
| 684 | −270,20 | 15.1 | 0.95,2.99 | 61.8 | 0.93,1.92 | 14.6 | 0.77,2.74 | 46.2 | 0.81,1.78 | 0.0 | 0.09,10.8 | 3.3 | 0.54,2.39 | 10.4 | 0.56,1.37 | 4.3 | 0.34,0.98 | 4.3 | 0.56,3.20 | 3.3 | 0.50,5.49 | ||
| IUI | 138 | 2279 | −75 | 22 | 1.96 | 84 | 1.36 | 21 | 1.74 | 53 | 0.88# | 0 | 1.56 | 3 | 0.70 | 15 | 0.92 | 9 | 0.87 | 1 | 0.22 | 1 | 0.28∧ |
| 644 | −230,79 | 15.9 | 1.06,3.62 | 60.9 | 0.89,2.09 | 15.2 | 0.89,3.43 | 38.4 | 0.54,1.43 | 0.0 | 0.14,17.0 | 2.2 | 0.21,2.28 | 10.9 | 0.50,1.68 | 6.5 | 0.46,1.67 | 0.7 | 0.03,1.64 | 0.7 | 0.04,1.99 | ||
| IVF with fresh-embryo cycles | 543 | 2274 | −96 # | 62 | 1.31# | 316 | 1.23# | 61 | 1.21# | 252 | 1.22# | 0 | 1.16 | 22 | 1.50 | 63 | 1.07 | 32 | 0.71 | 12 | 0.66 | 8 | 0.80# |
| 608 | −165,−27 | 11.4 | 0.90,1.90 | 58.2 | 0.98,1.55 | 11.2 | 0.81,1.81 | 46.4 | 0.95,1.57 | 0.0 | 0.11,12.5 | 4.1 | 0.96,2.35 | 11.6 | 0.79,1.45 | 5.9 | 0.48,1.05 | 2.2 | 0.32,1.36 | 1.5 | 0.33,1.94 | ||
| IVF with frozen-embryo cycles | 147 | 2368 | −40 | 16 | 1.35 | 68 | 0.76# | 22 | 1.84 | 58 | 0.89# | 0 | 1.00 | 1 | 0.25 | 9 | 0.54 | 12 | 0.75 | 4 | 0.85 | 0 | 0.77∧ |
| 653 | −189,109 | 10.9 | 0.64,2.86 | 46.3 | 0.50,1.17 | 15.0 | 0.95,3.55 | 39.5 | 0.55,1.44 | 0.0 | 0.09,11.1 | 0.7 | 0.03,2.06 | 6.1 | 0.26,1.12 | 8.2 | 0.38,1.50 | 2.7 | 0.25,2.95 | 0.0 | 0.21,2.80 | ||
| ICSI with fresh-embryo cycles | 380 | 2332 | −42 | 43 | 1.30 | 211 | 1.05# | 43 | 1.22 | 160 | 1.05 | 2 | 1.58 | 6 | 0.56# | 28 | 0.64 # | 35 | 1.15 | 12 | 0.96 | 8 | 1.22 |
| 653 | −138,53 | 11.3 | 0.83,2.03 | 55.5 | 0.81,1.37 | 11.3 | 0.76,1.95 | 42.1 | 0.77,1.43 | 0.5 | 0.15,17.2 | 1.6 | 0.26,1.23 | 7.4 | 0.43,0.94 | 9.2 | 0.77,1.71 | 3.2 | 0.47,1.98 | 2.1 | 0.50,2.95 | ||
| ICSI with frozen-embryo cycles | 65 | 2523 | 122 | 6 | 0.77∧ | 28 | 0.68 | 8 | 1.00∧ | 26 | 1.00 | 0 | 1.40 | 0 | 0.49∧ | 4 | 0.57 | 12 | 2.39 | 1 | 0.43 | 1 | 0.78 |
| 580 | −64,307 | 9.2 | 0.24,2.45 | 43.1 | 0.39,1.18 | 12.3 | 0.37,2.70 | 40.0 | 0.50,2.02 | 0.0 | 0.13,15.7 | 0.0 | 0.19,1.27 | 6.2 | 0.23,1.41 | 18.5 | 1.19,4.80 | 1.5 | 0.05,3.73 | 1.5 | 0.08,7.59 | ||
| Minimal medical intervention | 45 | 2529 | 133 | 2 | 0.54 | 18 | 0.65 | 1 | 0.30 | 20 | 1.21 | 0 | 1.48 | 0 | 0.86∧ | 2 | 0.37 | 2 | 0.58 | 0 | 0.65∧ | 0‡ | 0.20∧ |
| 491 | −38,303 | 4.4 | 0.14,2.12 | 40.0 | 0.29,1.47 | 2.2 | 0.05,2.02 | 44.4 | 0.51,2.87 | 0.0 | 0.14,16.2 | 0.0 | 0.54,1.36 | 4.4 | 0.09,1.52 | 4.4 | 0.19,1.77 | 0.0 | 0.30,1.38 | 0.0 | 0.02,1.85 | ||
| OI only | 63 | 2213 | −139 | 8 | 1.47 | 41 | 1.60 | 9 | 1.60 | 24 | 0.86 | 0 | 1.51 | 2 | 1.08 | 10 | 1.43 | 5 | 0.82 | 2 | 1.01 | ||
| 663 | −324,46 | 12.7 | 0.54,4.03 | 65.1 | 0.85,3.03 | 14.3 | 0.61,4.16 | 38.1 | 0.41,1.78 | 0.0 | 0.14,16.6 | 3.2 | 0.27,4.32 | 15.9 | 0.64,3.23 | 7.9 | 0.19,3.55 | 3.2 | 0.25,4.11 | ||||
Odds ratios account for clustering within mother, and are adjusted for maternal age, parity, baby's sex and whether twins same-sex.
Bold print signifies p<0.05.
19 births were missing 5 minute Apgar score information.
# Significant difference between effect for singletons and twins.
Model assumes common effect of twins on modality effects.
IF DX: Births to women who had a recorded diagnosis of infertility but no assisted conception treatment from a specialist clinic.
IF TX: Births as a result of spontaneous conception in women with a previous birth from assisted conception.
Data for neonatal death occurring in donor oocyte pregnancies collapsed in IVF and ICSI categories due to small numbers.
Data for neonatal death occurring in the groups minimal medical intervention and ovulation induction only combined due to small numbers.
Singletons and twins combined because of small numbers (comparator is twins).