Can sexual intercourse after embryo transfer increase the risk of miscarriage?

Sexual Intercourse After Embryo Transfer Does Not Increase Miscarriage Risk

There is no evidence showing that sexual intercourse after embryo transfer increases the risk of miscarriage. In fact, some evidence suggests it may have beneficial effects on implantation rates.

Evidence Assessment

Current Guidelines

The European Society of Human Reproduction and Embryology (ESHRE) guidelines do not mention sexual intercourse after embryo transfer as a risk factor for miscarriage 1. Their guidelines focus extensively on embryo transfer practices but do not list sexual activity as a contraindication or risk factor during the post-transfer period.

Research Evidence on Sexual Intercourse After Embryo Transfer

A randomized controlled trial by Tremellen et al. (2000) found that exposure to semen around the time of embryo transfer actually increased the likelihood of successful early embryo implantation and development 2. The study showed:

• No significant difference in pregnancy rates between intercourse and abstinence groups
• Higher proportion of viable embryos at 6-8 weeks in women exposed to semen (11.01% vs 7.69%)

A more recent randomized controlled trial (2023) found that sexual intercourse before embryo transfer may improve clinical pregnancy and implantation rates during frozen-thawed embryo transfer cycles 3:

• Higher clinical pregnancy rate in the intercourse group (51.72% vs 37.07%, p=0.045)
• Higher implantation rate in the intercourse group (38.31% vs 24.77%, p=0.005)
• No significant difference in spontaneous abortion rates between groups (11.67% vs 14.63%, p=0.662)

Potential Mechanisms and Considerations

Potential Benefits

• Exposure to seminal fluid may promote embryo development and implantation
• Seminal plasma contains factors that may modulate maternal immune response to the embryo

Potential Risks to Consider

While general evidence doesn't show increased miscarriage risk, there are rare case reports of complications:

• One case report described a heterotopic pregnancy after single embryo transfer where sexual intercourse occurred shortly before transfer 4. This is an extremely rare complication.

Actual Risk Factors for Miscarriage After Embryo Transfer

According to a large retrospective study of 15,210 pregnancies after embryo transfer 5, the significant risk factors for pregnancy loss include:

1. Maternal age:

   • Women 35-40 years: increased risk of early miscarriage (OR 1.49)
   • Women >40 years: increased risk of both early and late miscarriage (OR 3.82 and 2.79)

2. BMI:

   • Overweight: higher risk of late miscarriage (OR 1.38)
   • Obese: higher risk of both early and late miscarriage (OR 1.47 and 1.80)

3. Medical conditions:

   • PCOS: independent risk factor for late miscarriage (OR 1.58)
   • Uterine factors: higher risk of early miscarriage (OR 1.77)

4. Treatment factors:

   • Endometrial thickness: negative correlation with pregnancy loss
   • Frozen-thawed embryo transfer: slightly increased risk compared to fresh transfer (OR 1.12)
   • Number of embryos transferred: transferring three embryos showed higher risk of late miscarriage than single embryo transfer (OR 2.23)

Clinical Recommendations

1. Sexual intercourse after embryo transfer does not need to be restricted based on current evidence regarding miscarriage risk.

2. Focus on established risk factors for miscarriage after embryo transfer:

   • Counsel patients about modifiable risk factors like BMI
   • Consider age-related risks in treatment planning
   • Optimize management of conditions like PCOS
   • Consider endometrial thickness in transfer timing

3. Follow ESHRE guidelines for embryo transfer practices, which recommend elective single embryo transfer (eSET) for most patients to minimize multiple pregnancy risks 1, 6.

In summary, while patients may have concerns about sexual activity after embryo transfer, the evidence does not support restricting intercourse to prevent miscarriage. Clinical focus should remain on established risk factors for pregnancy loss following assisted reproduction.