Understanding the Menstrual Cycle and Fertility
The menstrual cycle is more than just your period—it’s a key window into your fertility. At the Southern California Center for Reproductive Medicine (SCCRM), we help individuals and couples understand their reproductive health from the inside out. One of the first steps? Learning more about your menstrual cycle and fertility, and what changes in cycle length could mean for your ability to conceive.
What is the menstrual cycle?
The menstrual cycle is your body’s monthly hormone-driven process that prepares for pregnancy. It’s divided into two main menstrual cycle phases:
1. Follicular phase
Begins on the first day of full menstrual bleeding and ends at ovulation.
During this phase, your brain signals the ovaries to mature follicles. One follicle becomes dominant and produces estrogen, helping the uterine lining grow in preparation for a possible pregnancy.
2. Luteal phase
Begins after ovulation and ends just before your next period.
After ovulation, progesterone helps stabilize the uterine lining. If no pregnancy occurs, hormone levels drop and your period begins, starting the cycle over again.
What can cycle length tell you about fertility?
Your cycle length (from the first day of bleeding to the day before your next period) can provide important fertility clues. Here’s what different cycle patterns might indicate:
Normal cycle: 24–35 days
Likely means regular ovulation
Suggests balanced hormones and good fertility health
Short cycle: less than 24 days
May indicate early ovulation or no ovulation
Can be linked to low ovarian reserve or age-related changes
Long or irregular cycle: more than 35 days
Often due to irregular or absent ovulation
Common with PCOS or thyroid hormone imbalances
Prolonged bleeding: more than 7 days
May be caused by hormonal imbalance, fibroids, or uterine polyps
Can impact implantation and make periods heavier and longer
No periods (Amenorrhea)
Strong sign that ovulation may not be occurring
Can result from very low or high body weight, stress, or hormonal issues
In some cases, could indicate early menopause or structural problems
FAQs: Common questions about your menstrual cycle and fertility
Can birth control hide irregular cycles?
Yes. Birth control can create the appearance of a regular cycle but does not indicate ovulation. Once off the pill or other hormonal birth controls, underlying issues like irregular ovulation may become more noticeable.
What if ovulation tests are always positive?
Some people—especially those with PCOS—have consistently high luteinizing hormone (LH) levels, which can result in false positives on ovulation predictor kits. Consistently testing positive on an ovulation kit may signal an ovulatory issue.
Can weight affect my cycle?
Absolutely. Being either underweight or overweight can disrupt hormone balance and lead to cycle irregularities. The good news is small changes can help – losing even just 5% of body weight can help with ovulation and chances of conception.
Is a 3–5 day period normal?
Yes. A period between 3 and 5 days is considered normal, as long as your cycle comes at regular intervals.
Could painful periods be a sign of a problem?
They might be. While mild cramping is normal, painful periods—especially those that interfere with daily activities—can signal endometriosis or another issue.
When should you see a fertility specialist?
We recommend seeking fertility support if:
You're under 35 and haven’t conceived after 12 months
You’re 35 or older and haven’t conceived after 6 months
You’re 40 or older
Your cycles are irregular, short, long, or absent
You’ve experienced two or more miscarriages
You suspect PCOS or another hormonal condition
You are LGBTQIA+ individuals or a couple ready to grow your family
Even if you’re not actively trying to conceive, cycle irregularities are worth evaluating. Early treatment can often restore hormonal balance and improve your fertility outlook.
Take charge of your reproductive health
Understanding your menstrual cycle phases and watching for cycle length changes can help you take proactive steps toward your fertility goals. At SCCRM, our team is here to guide you with compassion, clarity, and cutting-edge care.
Have questions about your cycle or fertility?
Contact SCCRM to schedule a consultation. We’re here to help.
Medical contributions by
Robert E. Anderson, M.D.
Double board-certified
Obstetrics and Gynecology, Reproductive Endocrinology and Infertility
With over 30 years experience in the field of Reproductive Medicine, Dr. Robert Anderson has developed a highly successful approach to the treatment of every type of fertility problem. He has been practicing in Orange County longer than any other Board Certified Reproductive Endocrinologist.
Don Royster, M.D.
Double board-certified
Obstetrics and Gynecology, Reproductive Endocrinology and Infertility
With over 15 years of experience as an OB/GYN and Reproductive Endocrinology and Infertility (REI) specialist, Dr. Don Royster joined SCCRM after serving on active duty in the United States Air Force for over 20 years, retiring at the rank of Colonel. He has performed over 6,000 surgeries and delivered over 1,000 babies with deployments and humanitarian missions across the globe.