How Do I Know If I'm Ovulating?

Luteinizing Hormone Plays A Critical Role in Ovulation

When you’re trying to get pregnant, knowing when you are ovulating is key. But, if you don’t understand how your body ovulates, it might feel like you’re playing the lottery. It’s time to be more strategic.

Your body uses two hormones to send messages between your brain and ovaries to mature and release an egg. The first hormone, Follicle Stimulating Hormone or FSH, tells your ovaries to mature an egg. When that egg matures, it sends a message to the brain that it’s ready. In return, the brain sends the second hormone, Luteinizing Hormone or LH, to tell that egg to release. LH will surge around 24 to 36 hours before the egg releases.

This is similar to ordering food from a delivery service. You send a message to the restaurant with your order. It takes time to cook, so you wait. Then, you receive a message that your food is ready, along with an approximate delivery time. With that time-frame in mind, you can be prepared for the delivery.

Knowing your LH levels can help you understand your ovulation window. And knowing your ovulation window can help you better time intercourse and improve your chances for conception.

Clinical Discussion

Hormonal changes during the follicular phase

Luteinizing hormone (LH), follicle stimulating hormone (FSH) and estrogen are especially critical during the follicular phase. The follicular phase starts during the first day of a woman’s menstrual cycle and ends when ovulation begins. During this phase, egg-containing shells, called follicles, grow. Eventually one follicle becomes dominant and produces a mature egg.

LH surge and the beginning of ovulation

To better understand the role that hormones have in the follicular phase, let’s start with LH and FSH. These hormones work together to stimulate egg growth and ultimately trigger ovulation. Here’s how it works – early in a woman’s cycle, FSH begins to increase and triggers egg development while LH levels remain low. At the midpoint of her cycle, the follicle matures and releases higher levels of estrogen. This increase in estrogen signals the pituitary gland to produce less FSH and more LH. This ‘surge’ in LH happens rapidly with most women and causes the mature egg to be released from the ovary.

Narrow window of fertility

During the process called ovulation, the egg will typically release 24 to 36 hours after the LH surge. This window of time is when the egg is available to be fertilized. If a woman can have intercourse within the next 24 hours, she has a greater chance to conceive, around 33%. If the egg is not fertilized during this window, it will dissolve and the woman will have to wait another month for another ovulation window.

Chances for pregnancy are low several days before ovulation

A note about sperm: sperm can typically live up to five days in the female body. Couples who are trying to conceive can begin to have intercourse in the days prior to ovulation. However, intercourse should be timed as close to ovulation as possible. If you only have intercourse 5 days before ovulation, your chances of getting pregnant are 10%.  Having intercourse on the day of ovulation increases your chances to around 33%.

conception, ovulation, female cycle

Medical News Today, Facts about sperm health and lifespan
NCBI, The Normal Menstrual Cycle and the Control of Ovulation
American Pregnancy Association: Understanding Ovulation
Cleveland Clinic: Pregnancy: Ovulation, Conception & Getting Pregnant

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