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Table 5 Stepwise Cox regression analysis on live birth probability of ART clinical pregnancies before 12 weeks of gestational age

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

Variables βa SEb HR 95% CI P
Maternal age (reference: <30)
 30–35 0.1196 0.1392 1.13 0.86–1.48 0.390
 36–40 0.5253 0.1956 1.69 1.15–2.48 0.007 *
  > 40 1.3087 0.3324 3.70 1.93–7.10 <0.001 *
COH protocol (reference: GnRH-a long protocol)
 GnRH-a short protocol 0.2526 0.1460 1.29 0.97–1.71 0.084
 GnRH antagonist protocol 1.2436 0.2953 3.47 1.94–6.19 <0.001 *
 Minimal stimulation protocol 1.1429 0.2310 3.14 2.00–4.93 <0.001 *
 GnRH-a rolonged protocol 0.0747 0.5109 1.08 0.40–2.93 0.884
 Other protocol 1.4356 0.5868 4.20 1.33–13.27 0.014 *
Cycle Type (reference: Fresh)
 Frozen 0.5059 0.1287 1.66 1.29–2.13 <0.001 *
Serum hCG levels 14 days after transfer (reference: < 695.30)
  ≥ 695.30 −1.6353 0.1687 0.19 0.14–0.27 <0.001 *
  1. HR hazard ratio, CI confidence interval, *P<0.05
  2. aβ is the estimated parameter of the regression model
  3. bSE is the standard error of the regression model