In vitro fertilisation for unexplained subfertility

Background: In vitro fertilisation (IVF) is a treatment for unexplained subfertility but is invasive, expensive, and associated with risks.

Objectives: To evaluate the effectiveness and safety of IVF versus expectant management, unstimulated intrauterine insemination (IUI), and IUI with ovarian stimulation using gonadotropins, clomiphene citrate (CC), or letrozole in improving pregnancy outcomes.

Search methods: We searched following databases from inception to November 2021, with no language restriction: Cochrane Gynaecology and Fertility Register, CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL. We searched reference lists of articles and conference abstracts.

Selection criteria: Randomised controlled trials (RCTs) comparing effectiveness of IVF for unexplained subfertility with expectant management, unstimulated IUI, and stimulated IUI.

Data collection and analysis: We followed standard Cochrane methods.

Main results: IVF versus expectant management (two RCTs) We are uncertain whether IVF improves live birth rate (LBR) and clinical pregnancy rate (CPR) compared to expectant management (odds ratio (OR) 22.0, 95% confidence interval (CI) 2.56 to 189.37; 1 RCT; 51 women; very low-quality evidence; OR 3.24, 95% CI 1.07 to 9.8; 2 RCTs; 86 women; I² = 80%; very low-quality evidence). Adverse effects were not reported. Assuming 4% LBR and 12% CPR with expectant management, these would be 8.8% to 9% and 13% to 58% with IVF. IVF versus unstimulated IUI (two RCTs) IVF may improve LBR compared to unstimulated IUI (OR 2.47, 95% CI 1.19 to 5.12; 2 RCTs; 156 women; I² = 60%; low-quality evidence). We are uncertain whether there is a difference between IVF and IUI for multiple pregnancy rate (MPR) (OR 1.03, 95% CI 0.04 to 27.29; 1 RCT; 43 women; very low-quality evidence) and miscarriage rate (OR 1.72, 95% CI 0.14 to 21.25; 1 RCT; 43 women; very low-quality evidence). No study reported ovarian hyperstimulation syndrome (OHSS). Assuming 16% LBR, 3% MPR, and 6% miscarriage rate with unstimulated IUI, these outcomes would be 18.5% to 49%, 0.1% to 46%, and 0.9% to 58% with IVF. IVF versus IUI + ovarian stimulation with gonadotropins (6 RCTs), CC (1 RCT), or letrozole (no RCTs) Stratified analysis was based on pretreatment status. Treatment-naive women There may be little or no difference in LBR between IVF and IUI + gonadotropins (1 IVF to 2 to 3 IUI cycles: OR 1.19, 95% CI 0.87 to 1.61; 3 RCTs; 731 women; I² = 0%; low-quality evidence; 1 IVF to 1 IUI cycle: OR 1.63, 95% CI 0.91 to 2.92; 2 RCTs; 221 women; I² = 54%; low-quality evidence); or between IVF and IUI + CC (OR 2.51, 95% CI 0.96 to 6.55; 1 RCT; 103 women; low-quality evidence). Assuming 42% LBR with IUI + gonadotropins (1 IVF to 2 to 3 IUI cycles) and 26% LBR with IUI + gonadotropins (1 IVF to 1 IUI cycle), LBR would be 39% to 54% and 24% to 51% with IVF. Assuming 15% LBR with IUI + CC, LBR would be 15% to 54% with IVF. There may be little or no difference in CPR between IVF and IUI + gonadotropins (1 IVF to 2 to 3 IUI cycles: OR 1.17, 95% CI 0.85 to 1.59; 3 RCTs; 731 women; I² = 0%; low-quality evidence; 1 IVF to 1 IUI cycle: OR 4.59, 95% CI 1.86 to 11.35; 1 RCT; 103 women; low-quality evidence); or between IVF and IUI + CC (OR 3.58, 95% CI 1.51 to 8.49; 1 RCT; 103 women; low-quality evidence). Assuming 48% CPR with IUI + gonadotropins (1 IVF to 2 to 3 IUI cycles) and 17% with IUI + gonadotropins (1 IVF to 1 IUI cycle), CPR would be 44% to 60% and 28% to 70% with IVF. Assuming 21% CPR with IUI + CC, CPR would be 29% to 69% with IVF. There may be little or no difference in multiple pregnancy rate (MPR) between IVF and IUI + gonadotropins (1 IVF to 2 to 3 IUI cycles: OR 0.82, 95% CI 0.38 to 1.77; 3 RCTs; 731 women; I² = 0%; low-quality evidence; 1 IVF to 1 IUI cycle: OR 0.76, 95% CI 0.36 to 1.58; 2 RCTs; 221 women; I² = 0%; low-quality evidence); or between IVF and IUI + CC (OR 0.64, 95% CI 0.17 to 2.41; 1 RCT; 102 women; low-quality evidence). We are uncertain if there is a difference in OHSS between IVF and IUI + gonadotropins with 1 IVF to 2 to 3 IUI cycles (OR 6.86, 95% CI 0.35 to 134.59; 1 RCT; 207 women; very low-quality evidence); and there may be little or no difference in OHSS with 1 IVF to 1 IUI cycle (OR 1.22, 95% CI 0.36 to 4.16; 2 RCTs; 221 women; I² = 0%; low-quality evidence). There may be little or no difference between IVF and IUI + CC (OR 1.53, 95% CI 0.24 to 9.57; 1 RCT; 102 women; low-quality evidence). We are uncertain if there is a difference in miscarriage rate between IVF and IUI + gonadotropins with 1 IVF to 2 to 3 IUI cycles (OR 0.31, 95% CI 0.03 to 3.04; 1 RCT; 207 women; very low-quality evidence); and there may be little or no difference with 1 IVF to 1 IUI cycle (OR 1.16, 95% CI 0.44 to 3.02; 1 RCT; 103 women; low-quality evidence). There may be little or no difference between IVF and IUI + CC (OR 1.48, 95% CI 0.54 to 4.05; 1 RCT; 102 women; low-quality evidence). In women pretreated with IUI + CC IVF may improve LBR compared with IUI + gonadotropins (OR 3.90, 95% CI 2.32 to 6.57; 1 RCT; 280 women; low-quality evidence). Assuming 22% LBR with IUI + gonadotropins, LBR would be 39% to 65% with IVF. IVF may improve CPR compared with IUI + gonadotropins (OR 14.13, 95% CI 7.57 to 26.38; 1 RCT; 280 women; low-quality evidence). Assuming 30% CPR with IUI + gonadotropins, CPR would be 76% to 92% with IVF.

Authors' conclusions: IVF may improve LBR over unstimulated IUI. Data should be interpreted with caution as overall evidence quality was low.