I'm a gynecologist who has helped women navigate intimacy issues for more than 25 years. Here's 6 things I wish every woman knew about desire.

• Maria Sophocles has been a gynecologist for more than 25 years and focuses on women's sexual health.
• She says that it's normal for women's libido to fluctuate because of several biological reasons.

This as-told-to essay is based on a conversation with Maria Sophocles, a gynecologist focusing on women's sexual health. The following has been edited for length and clarity.

I've worked as a gynecologist for more than 25 years, and I've come across many patients who just weren't in the mood. Some said their low libido wasn't a problem for them — but they said it could create tension with their partner. Others told me that they missed feeling desire.

Unfortunately, low libido is very common. More than a quarter of premenopausal women experience low desire, and more than half of menopausal women do. While you're not alone if you have low desire, there are things you can do to take control of your libido. Here are six things I wish all women knew about female desire and libido.

It's normal for libido to fluctuate

Many women feel frustrated that their libido isn't consistent. They see messages in movies and on social media that they should strive to have an intense libido all the time. But that's just not realistic. First, we're humans with moods, tiredness, and family obligations that can affect our desire to get busy. But beyond that, there are also biological reasons your libido isn't consistent.

If you accept that and permit yourself to have normal fluctuations in desire, you help to take away the pressure you might feel to crave sex every day.

Estrogen can encourage desire

The more you understand the relationship between hormones and libido, the more you understand the shifts in your level of desire. Estrogen, which rises during the first half of the menstrual cycle, can contribute to feelings of desire. In particular, one type of estrogen — estradiol — is so effective in encouraging libido that it's been used to treat low libido.

You might feel extra randy as estrogen levels increase and peak during ovulation. There's a biological reason for this — from a survival perspective, it makes sense to have an interest in sex at the time your body has an egg to fertilize.

Progesterone makes you want to sleep — and less likely to want sex

After ovulation (and during menopause), your estrogen levels fall. Decreasing estrogen can leave you feeling less amorous.

At the same time, there's another hormone inhibiting your libido: progesterone. Progesterone rises during the second half of the menstrual cycle. Progesterone is a pro-sleep hormone that releases the neurotransmitter GABA, which encourages healthy sleep. When we're excited to sleep, we're less likely to be excited about sex.

Your emotions and your background matter too

That's interesting, but when patients come to me, they don't say, "My hormones are tanking my sex drive." Instead, they mention the way that a low sex drive is affecting their relationships. So I have a behavioral-health approach to speaking with them.

First, I ask them to consider what might be impeding their sex drive. Are they struggling with body image? Are they frustrated with their partner? Recovering from an affair? Adjusting to having a new baby?

Next, I ask them about their background with intimacy. Is sex something they enjoy or do because they feel they have to? Have they felt desire in the past? Working through these questions can be difficult, but speaking with a counselor or a sex therapist can help.

Reading racy scenes can ignite your sex life

Bibliotherapy, or reading racy books, can increase desire in many women. Women who read, hear, or see sexy stimuli store those sensations in their brains and are more likely to show interest in sex.

So, pick up a romance novel for your beach read, or give erotica a try. Watch movies or shows with steamy sex scenes or listen to audio porn.

Start G-rated with your partner

Many women find it frustrating when their partner only wants — or rushes toward — penetrative sex. So, I give patients a challenge: start G-rated. Cuddle on the couch or play a game together after the kids are in bed. Spend at least half an hour connecting (and no, talking about kids, taxes, and bills doesn't count).

When you're ready to move on, either the same day or another, get PG. Kiss and touch, but don't skip straight to sex. Slowly, move your make-outs to PG-13 and R-rated before you get to anything X-rated.

There's a lot that goes into sexual desire. It's not just hormones or the connection with your partner — it's a multifaceted, complex combination of many things in your life. The most important step is to allow yourself to want a healthy, thriving sex life.