What does it mean to have a dominant follicle in the left ovary?

Understanding a Dominant Follicle in the Left Ovary

A dominant follicle in the left ovary simply means that during your current menstrual cycle, a mature egg-containing follicle has developed in your left ovary and is preparing for ovulation.

What Is a Dominant Follicle?

A dominant follicle is a normal part of your reproductive cycle. Here's what it means in simple terms:

• Each month, several small follicles (fluid-filled sacs containing immature eggs) begin to develop in your ovaries
• Usually only one follicle becomes "dominant" - growing larger than the others (typically >15mm)
• The other follicles stop growing and eventually disappear
• The dominant follicle will release a mature egg during ovulation

The Normal Follicular Development Process

During a typical menstrual cycle:

1. Early cycle (days 1-7): Multiple small follicles (2-8mm) begin developing in both ovaries
2. Selection phase (around day 5-7): One follicle is "selected" to become dominant
3. Growth phase: The dominant follicle continues growing while others regress
4. Pre-ovulation: The dominant follicle reaches 18-25mm before releasing the egg

According to the Ovarian-Adnexal Reporting and Data System (O-RADS), follicles are considered normal physiologic structures when they appear as simple cysts less than 3cm in diameter 1.

Why the Left Ovary?

The side where the dominant follicle develops is completely normal and varies from cycle to cycle:

• Ovulation can occur from either ovary
• Some women may alternate between ovaries each month
• Others may have dominant follicles appear more frequently on one side
• Interestingly, some research suggests that when ovulation jumps from the left ovary to the right ovary in successive cycles, it may increase chances of pregnancy during fertility treatments 2

What This Means For You

Finding a dominant follicle on ultrasound is a positive sign that:

• Your ovaries are functioning normally
• You are likely in the pre-ovulatory phase of your cycle
• Ovulation is expected to occur soon (within 24-48 hours of the follicle reaching maximum size)

When Dominant Follicles Are Monitored

Dominant follicles are commonly monitored in:

• Fertility tracking for natural conception
• Timing for intrauterine insemination (IUI)
• Monitoring response during fertility treatments
• Evaluating ovulatory function

For women undergoing fertility evaluation, transvaginal ultrasound is the preferred method to monitor follicular development, as it can accurately track follicle growth and determine when ovulation is likely to occur 1.

Key Points to Remember

• A dominant follicle in the left ovary is completely normal
• It indicates your reproductive system is working as expected
• The location (left vs. right ovary) has no medical significance for most women
• This is a natural part of your menstrual cycle that happens every month

If you're tracking your fertility, the presence of a dominant follicle is a positive sign that ovulation is approaching, which is the optimal time for conception.