What is the best time to have sex after the luteinizing hormone (LH) surge to conceive?

Optimal Timing for Sexual Intercourse After LH Surge for Conception

The best time to have sexual intercourse for conception is 1 day after detecting the LH surge, as this timing results in significantly higher pregnancy rates compared to later timing. 1, 2

Understanding the LH Surge and Ovulation Timeline

• Ovulation typically occurs 24-36 hours after the initial rise in luteinizing hormone (LH), or approximately 8-20 hours after the LH peak 1, 3
• The fertile window spans approximately 6 days, ending on the day of ovulation 4
• Pregnancy is most likely when intercourse occurs within 24-48 hours after detecting the LH surge 1

Evidence-Based Recommendations for Timing

For Natural Conception:

1. Have intercourse 1 day after detecting the LH surge (highest probability of conception) 1, 2
2. Continue intercourse daily for 1-2 days after the first intercourse to maximize chances
3. The probability of conception ranges from:
   • 0.10 (10%) when intercourse occurs five days before ovulation
   • 0.33 (33%) when intercourse occurs on the day of ovulation itself 4

For Intrauterine Insemination (IUI):

• IUI in natural cycles should be performed 1 day after LH rise 5, 1
• A randomized controlled trial showed significantly higher clinical pregnancy rates with IUI performed 1 day after LH rise (19.7%) compared to 2 days after (11.1%) 2

Additional Factors That Affect Conception

Cervical Mucus Quality

• Strong evidence indicates that cervical mucus quality is actually a better predictor of conception than timing alone 6
• Optimal mucus quality (clear, stretchy, slippery) indicates peak fertility
• Intercourse on days with optimal mucus quality maximizes conception chances regardless of exact timing relative to ovulation 6

Sperm and Egg Viability

• Sperm can survive up to 5 days in favorable cervical mucus
• The egg is viable for approximately 12-24 hours after ovulation
• Most conceptions (94%) result from sperm less than 3 days old 4

Common Pitfalls to Avoid

1. Waiting too long after LH surge - Delaying intercourse to 2 days after LH surge significantly reduces pregnancy rates 2
2. Focusing only on the day of ovulation - The entire 6-day window ending on ovulation day is fertile 4
3. Ignoring cervical mucus signs - Mucus quality can be as important as timing based on LH 6
4. Infrequent intercourse - Having intercourse only once during the fertile window may reduce chances
5. Mistiming due to irregular testing - Inconsistent LH testing may miss the surge

Algorithm for Maximizing Conception Chances

1. Begin LH testing according to kit instructions (typically 2-3 days before expected ovulation)
2. Test at the same time daily, preferably morning urine samples
3. Once LH surge is detected:
   • Have intercourse within 24 hours (1 day after surge)
   • Continue daily intercourse for 1-2 more days
4. Monitor cervical mucus quality - prioritize intercourse when mucus is clear and stretchy
5. For those using IUI, schedule the procedure exactly 1 day after LH rise for optimal results 5, 2

By following these evidence-based recommendations, you can significantly increase your chances of conception by ensuring intercourse occurs during your most fertile period.