External Friction and Its Impact on Fertility Risks

Extracorporeal friction

During the high-risk period, external friction for about 2 minutes followed by taking emergency contraception 25 hours later, and experiencing bleeding a week later, would result in a pregnancy probability of less than 1% or even one in a billion.
What is the minimum number of sperm required for fertilization? How many sperm are typically found in pre-ejaculatory fluid? Is "ejaculatory force" necessary to help sperm swim towards the egg for conception?

Niming, 10~19 year old female. Ask Date: 2019/04/11

Dr. Huang Jianzhong reply Obstetrics and Gynecology

The risk period for external friction is approximately 2 minutes, and taking emergency contraception 25 hours later, with bleeding occurring a week after, results in a pregnancy probability of less than one in a billion.

Regarding the number of sperm required for fertilization, it is generally understood that a significant number of sperm are needed, but the exact number can vary.
Prostate fluid contains sperm, but the amount can vary based on several factors.

Fertilization does not require "ejaculation force" to assist sperm in reaching the egg.

Reply Date: 2019/04/11

More Info

Understanding external friction and its impact on fertility risks involves several biological and physiological factors. When discussing the potential for pregnancy, it is crucial to consider the mechanics of sperm transfer, the viability of sperm, and the timing of ovulation.

Firstly, the scenario you described involves external friction, which typically refers to physical contact that may occur during sexual activity without penetration. In such cases, the risk of pregnancy is significantly lower compared to penetrative intercourse. The primary reason for this is that sperm must travel through the female reproductive tract to reach the egg for fertilization to occur. If sperm is deposited outside the vagina, the chances of it entering the reproductive tract are minimal.

Regarding the use of emergency contraception (the "morning-after pill"), taking it within 72 hours after unprotected intercourse can significantly reduce the risk of pregnancy. If taken after a potential fertilization window, its effectiveness diminishes. The bleeding you experienced a week later could be a side effect of the hormonal changes induced by the emergency contraceptive, rather than an indication of pregnancy.

In terms of sperm count, studies suggest that a minimum of about 15 million sperm per milliliter is necessary for a reasonable chance of conception. However, the total number of sperm needed for successful fertilization can vary based on several factors, including the health and motility of the sperm. Pre-ejaculatory fluid (pre-cum) can contain sperm, but the concentration is generally lower than in ejaculate. The presence of sperm in pre-ejaculatory fluid can still pose a risk for pregnancy, albeit a lower one.

The concept of "射力" or the force of ejaculation is indeed relevant in the context of sperm motility. During ejaculation, sperm are propelled into the female reproductive tract, which aids their movement toward the egg. This forceful expulsion is crucial for increasing the likelihood of sperm reaching the egg, as it helps overcome the natural barriers present in the female anatomy.

In summary, while external friction may pose a minimal risk for pregnancy, the likelihood is significantly reduced compared to penetrative intercourse. The effectiveness of emergency contraception, the sperm count necessary for fertilization, and the mechanics of sperm movement all play critical roles in understanding fertility risks. If you have further concerns about fertility or contraception, consulting a healthcare provider can provide personalized guidance and information.

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