Natural cycle vs IUI

The natural journey of sperm

In an ideal world with two young healthy and fertile partners, approximately 200 million sperm are ejaculated into the vagina. But as you will see there is such incredible attrition at each “stage,” that this number quickly plummets to the mere thousands. Of those 200 million, roughly 1 million make it through the cervix and into the uterus due to flow back, the acidic environment of the vagina, and the small passage of the cervix.

From that 1 million, only 10k make it to the top of the uterus. The rest are attacked and absorbed by white blood cells or otherwise fail to swim properly and die off. From the 10,000 sperm cells that make it to the top of the uterus, only about 1,000 enter the fallopian tube carrying the egg; and still, the journey is not over. Given this, there is only about a 20% chance of conception each month even in the best of circumstances.

Major Types of IUI Procedure Cycles

IUI can be conductes during a natural cycle depending on your preferences, history and fertility diagnostic testing . Most often you be treayed with medications that will stimulate egg growth and help time your ovulation with the insemination

The Natural cycle In a Natural IUI Cycle, the woman takes no drugs. She will grow a follicle and ovulate naturally. The goal here is to get sperm to the right place at the right time.

The Trigger cycle The Trigger Only IUI Cycle is essentially a natural cycle that uses a medication to “trigger” ovulation and optimally time the insemination. The IUI takes place 12-36 hours after the trigger medication is administered. Trigger shots are typically used in both oral medicines and injectable medication cycles as well.

Oral Med cycle An oral medication cycle uses letrozole, which stimulates the release of FSH and LH. FSH and LH further orchestrate follicular and egg development and ovulation. Oral medication cycles have the benefit of increasing conception and live birth rates while having less risk of multiples as injectable gonadotropin medications.

Injectable Med cycle Injectable gonadotropin medications are used for IUI procedures (typically after having a previous failed IUIs) to stimulate the ovaries further and improve the odds of conception. The increased odds of conception come with the risk of increased odds of multiples and must be managed carefully through ultrasound and blood work monitoring to ensure too many follicles are not developing. While still relatively uncommon, cycle cancelations or IVF conversions are more common when using injectable medications compared to when oral medications like letrozole are used.

US and blood monitoring Ultrasound and blood “monitoring” are office appointments to check on how your uterine lining, follicles, eggs, and hormone levels are progressing during the IUI process. They are the best way to ensure a safe and effective IUI treatment cycle. They are mandatory for most oral and injectable intrauterine insemination cycles.

No monitoring + OPK For those doing natural IUI (frequently done for those with regular cycles and minimal fertility factors and female-only couples), and some oral medication IUI procedures, one may use an Ovulatory Predictor Kit (OPK) to know when they’re ovulating. Simply come into the office one or two times for the intrauterine insemination.

How It Works and What to Expect

The IUI Process

The exact process of an IUI treatment cycle is largely determined by two decisions: which (if any) drugs are used and whether or not office monitoring is done. Despite the slight differences, all IUI processes follow the same general biological and procedural stages.

Day 1 of cycle – Call with day one of your period.

For Anovulatory Patients (or those with otherwise absent/infrequent cycles)

medications and thus the IUI cycle can start at any time. However, if the uterine lining is abnormally thick at baseline (>10mm), one will likely need a 7 to 10-day course of progesterone to cause the onset of a period.  

Day 2-12(ish)  Follicular, Egg, and Lining.

Development  The first phase of an IUI is the development of your follicles/eggs and uterine lining. As mentioned above, this can be done with or without medications but is most often done with medications to help egg development, increase the odds of conception, and thus the odds of a live birth. Medications are often started on days 2-4 of your cycle after your baseline appointment. Letrozole is usually taken for 5 days. Gonadatropins are usually taken for around 10 days. Blood and ultrasound monitoring often accompany this part of the cycle to help us determine the follicular and lining growth, adjust medications if necessary, and ensure the cycle is conducted in a safe and calculated way.  

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