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Blog /Insemination Syringes: What’s the Best Length and Size for Conception?

Insemination Syringes: What’s the Best Length and Size for Conception?

How does syringe size affect my conception chances?

When families are researching options for home insemination, they understandably have questions about those options:

“How does this compare to other ways I’ve tried to get pregnant?”
“How will this option work for me and my body?”
“I’m tall. Could my height negatively impact the effectiveness?”
“Why would this potentially work, when other tries at pregnancy haven’t?”

At Mosie, we have had a number of questions from families asking about the size and length of the Mosie syringe in the Mosie Baby Kit for home insemination. So how does syringe size affect your conception chances? Let’s take a closer look at the design of the Mosie syringe and why its very specific design has helped so many families.

Sized for Real Vaginal Length (Busting Vaginal Length Myths)

So why is the Mosie syringe a mere 3.5 inches in length and certainly more slender than the average penis? To start, let’s take a peek at some numbers.

While penises come in all shapes and sizes, research has found that the average penis is about 5 inches long when it’s erect. Obviously home insemination is not the same as intercourse. Still, it’s not always intuitive why a slender little syringe is being tasked with the same job as a human penis. (For more about this, you may want to visit our article How is Home Insemination Different Than Intercourse?)

Fun fact: Both penises and vaginas tend to change in length when aroused:

A Cucumber, pepper, and mosie to represent different sizes of body parts

When the average vagina is relaxed and not aroused, it is only about 3 inches in length. While research on vaginal size is limited, a 2006 study used data from MRI scans on 28 women of different ethnicities ranging from 18 to 39 years to give us a better sense of vaginal size. They found a range 1.6 inches to 3.7 inches in length. So again, vaginas aren’t nearly as big as we usually think!

Even though the vaginal canal can stretch quite a bit for a number of different (ahem) purposes, its resting–or default–size is actually pretty modest.

When Marc and Maureen started developing the Mosie syringe, one of the questions they had for a fertility specialist was, “Is it big enough?” They wanted to make sure we thoroughly researched what size syringe would give people the greatest chances at conception success.

Thus, the Mosie syringe was designed so that the part of the syringe inserted into the vagina is right at 3.5 inches in length.

Sized to Deliver Sperm to the Cervix 

Now that we know more about the length of vaginas, why exactly does that matter when it comes to conception and making a baby?

Your cervix lies at the top of the vaginal canal and functions like a portal into the uterus and fallopian tubes beyond. As Mosie founder Maureen demonstrates in this video, your cervix plays an important role in conception and it goes through 2 important changes as you approach ovulation:
  1. The cervix softens and opens more, to allow sperm to enter the uterus.
  2. The cervix produces cervical mucus that helps sperm move through the cervix to get to an egg.

For conception to happen, sperm needs to arrive at the cervical opening at this moment, when your cervix is primed for baby-making. What we don’t want to do is spray sperm all over the vaginal walls. Rather, to maximize the number of sperm who reach the cervix and enter the uterus, you want that sperm to be delivered as close to the cervical opening as possible where they make use of the increased mucus and the larger opening to get to their goal: Finding the egg! A well-designed home insemination syringe can help you do this.

For example, if you use a large syringe that’s not intended for home insemination, you’re more at risk of delivering the sperm sample at the vaginal wall.

Sized for Comfort

While the design of the Mosie syringe is driven first by function, it’s also very much made to maximize ease and comfort when inseminating. Trying to get pregnant has enough emotional and physical challenges, so when Maureen and Marc designed Mosie, they really wanted to make sure the syringe was as comfortable to use as possible.

This can be especially helpful for some of our families who are dealing with any pain or discomfort during sex or in the vulva and vaginal structures. Dyspareunia (pain during sex), including Vaginismus and Vulvadynia, scar tissue or other conditions can make vaginal penetration uncomfortable. So Mosie was carefully designed with no rough edges and a slender, tampon-like diameter to make insertion as gentle and easy as possible.


Still have questions?  


Belladelli F, Del Giudice F, Glover F, Mulloy E, Muncey W, Basran S, Fallara G, Pozzi E, Montorsi F, Salonia A, Eisenberg ML.Worldwide Temporal Trends in Penile Length: A Systematic Review and Meta-Analysis. World J Mens Health. 2023 Oct;41(4):848-860. doi: 10.5534/wjmh.220203. Epub 2023 Feb 15. PMID: 36792094; PMCID: PMC10523114.

King BM. Average-Size Erect Penis: Fiction, Fact, and the Need for Counseling. (2020). J Sex Marital Ther. 2021;47(1):80-89. doi: 10.1080/0092623X.2020.1787279. Epub 2020 Jul 15. PMID: 32666897.

Kurt T. Barnhart, Adriana Izquierdo, E. Scott Pretorius, David M. Shera, Mayadah Shabbout, Alka Shaunik.Baseline dimensions of the human vagina. Human Reproduction, Volume 21, Issue 6, June 2006, Pages 1618–1622.

Masters, William H. and Johnson, Virginia E. (1966). Human Sexual Inadequacy. The Journal of Sex Research, Vol. 6, No. 3 (Aug., 1970).


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