ICI vs Natural Sex Success Rates
For couples using donor sperm, intracervical insemination (ICI) shows no substantial benefit over natural intercourse in terms of pregnancy outcomes, while intrauterine insemination (IUI) provides significantly better results than both ICI and natural conception attempts.
Direct Comparison: ICI vs Natural Intercourse
The evidence comparing ICI to natural intercourse is limited, but the available data suggests minimal advantage for ICI:
In couples with good cervical mucus function (≥5 motile sperm per high-powered field on postcoital testing), ICI showed pregnancy rates of 4.8% per cycle compared to natural intercourse, with no statistically significant difference 1
Natural cycle ICI with donor sperm achieved cumulative ongoing pregnancy rates of 37.9% over six cycles, which is only modestly better than expectant management rates of 17% reported for unexplained infertility 2, 3
The European Society of Human Reproduction and Embryology found that natural cycle IUI shows only a 23% success rate versus 17% for expectant management in unexplained infertility, suggesting ICI would fall somewhere between these values 4
IUI Substantially Outperforms Both ICI and Natural Intercourse
The most clinically relevant finding is that IUI dramatically outperforms ICI, making the ICI vs natural sex comparison less relevant in practice:
IUI provides a 15% absolute improvement in live birth rates over ICI when using donor sperm, according to the American College of Obstetricians and Gynecologists 4
The Cochrane systematic review demonstrated that IUI significantly improved both live birth rates (OR 1.98,95% CI 1.02-3.86) and pregnancy rates (OR 3.37,95% CI 1.90-5.96) compared to ICI after 6 cycles 5
IUI in natural cycles improves conception probability over timed intercourse with an odds ratio of 2.43 (95% CI: 1.54-3.83), as reported by the National Institute for Health and Care Excellence 4
Clinical Context Matters
The success of any insemination method depends heavily on the underlying fertility prognosis:
For couples with good prognosis (Hunault score 30-40%, indicating >30% chance of natural conception within 12 months), expectant management for at least 6 months should be the first option, as IUI with ovarian stimulation does not significantly improve live birth rates (RR 0.85,95% CI 0.63-1.1) 3
For couples with poor prognosis (Hunault score <30%), IUI with ovarian stimulation significantly increased cumulative live birth rates compared to expectant management (OR 3.4,95% CI 1.7-6.8) 3
For male factor infertility with poor postcoital tests (≤3 motile sperm per HPF), IUI achieved 8.3% pregnancy rate per cycle versus 0% for ICI, a statistically significant difference (P=0.04) 1
Practical Algorithm for Clinical Decision-Making
Step 1: Assess fertility prognosis
- Calculate Hunault score or estimate natural conception probability over next 12 months 3
Step 2: If prognosis >30% natural conception probability
- Recommend expectant management with timed intercourse for 6 months 3
- ICI offers no proven advantage in this population 1
Step 3: If prognosis <30% natural conception probability
- Skip ICI entirely and proceed directly to IUI, as ICI provides minimal benefit over natural intercourse 4, 5
- IUI with ovarian stimulation is the recommended first-line treatment 3
Step 4: For donor sperm insemination
Important Caveats
ICI has essentially been superseded by IUI in modern practice due to superior outcomes, making direct ICI vs natural sex comparisons of limited clinical utility 4, 5
The quality of evidence directly comparing ICI to natural intercourse is low, with most studies being small and retrospective 1
All insemination methods show declining success with increasing female age, with a hazard ratio of 0.94 per year for ongoing pregnancy 2
Multiple pregnancy rates and ovarian hyperstimulation syndrome risks must be considered when adding ovarian stimulation to any insemination method 3