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Table 2 Cox analysis of risk of pregnancy loss throughout pregnancy in ART clinical pregnancies

From: Influencing factors of pregnancy loss and survival probability of clinical pregnancies conceived through assisted reproductive technology

Variables No. of PL/total
(685/ 5485)
PL rate HR (95% CI)a P a
Maternal age
  < 30 292/2556 11.4% 1.00[Reference]  
 30–35 283/2361 12.0% 1.06(0.90–1.25) 0.508
 36–40 84/472 17.8% 1.63(1.28–2.08) <0.001 *
  > 40 20/53 37.7% 4.14(2.63–6.52) <0.001 *
 Ptrend    1.31(1.17–1.45) <0.001 *
Maternal BMI
  < 18.5 50/509 9.8% 0.85(0.63–1.13) 0.260
 18.5–25 487/4009 12.1% 1.00[Reference]  
 25–28 97/641 15.1% 1.24(1.00–1.55) 0.051
  ≥ 28 42/235 17.9% 1.52(1.11–2.10) 0.010 *
Paternal BMI
  < 18.5 9/103 8.7% 0.67(0.33–1.35) 0.264
 18.5–25 405/3309 12.2% 1.00[Reference]  
 25–28 189/1344 14.1% 1.15(0.96–1.37) 0.120
  ≥ 28 69/603 12.3% 0.95(0.74–1.23) 0.691
Infertility type
 Primary 337/2781 12.1% 1.00[Reference]  
 Secondary 319/2466 12.9% 0.99(0.85–1.16) 0.908
COH protocold
 GnRH-a long protocol 391/3406 11.5% 1.00[Reference]  
 GnRH-a short protocol 186/1573 11.8% 0.93(0.77–1.11) 0.373
 GnRH antagonist protocol 35/95 36.8% 3.49(2.46–4.94) <0.001 *
 Minimal stimulation protocol 44/186 23.7% 1.83(1.31–2.54) <0.001 *
 GnRH-a rolonged protocol 12/123 9.8% 0.84(0.48–1.50) 0.689
 Other protocol 5/13 38.5% 3.70(1.53–8.95) 0.004 *
The total Gn doseb
  < 1808.01 373/3181 11.7% 1.00[Reference]  
  ≥ 1808.01 301/2208 13.6% 1.12(0.96–1.30) 0.161
Fertilization methods
 IVF 579/4543 12.7% 1.00[Reference]  
 ICSI 98/875 11.2% 0.87(0.70–1.08) 0.205
Cycle type
 Fresh 282/2675 10.5% 1.00[Reference]  
 Frozen 337/2477 13.6% 1.30(1.11–1.53) 0.001 *
No. of embryos transferred
 1 82/474 17.3% 1.00[Reference]  
 2 516/4324 11.9% 0.71(0.56–0.90) 0.005 *
 3 84/637 13.2% 0.67(0.49–0.91) 0.010 *
 Ptrend    0.81(0.69–0.96) 0.012 *
Cleavage-stage embryo or blastocystd
 Cleavage-stage embryo 466/3860 12.1% 1.00[Reference]  
 Blastocyst 198/1405 14.1% 1.10(1.01–1.19) 0.030 *
Serum hCG levels 14 days after transferc
  < 695.30 334/2205 15.1% 1.00[Reference]  
  ≥ 695.30 115/1988 5.8% 0.36(0.29–0.45) <0.001 *
  1. aAdjusted for maternal age
  2. bThe cutoff value was the mean of total Gn dose in cycle
  3. cThe cutoff value was the mean of serum hCG levels 14 days after transfer
  4. dGnRH antagonist protocol was not utilized in Changzhou, and they only transferred cleavage-stage embryos