Luteal Phase – What It Is and It’s Relation to Pregnancy

A menstrual cycle consists of 3 phases, namely ovulatory, luteal, and follicular. Each phase of the menstrual cycle has its own importance in fertilising the ovum and making you pregnant. If you aren’t pregnant, it also sheds the unused endometrial lining at the termination of the cycle. This article is about the luteal phase, and its relation to pregnancy.

What Is the Luteal Phase?

The period between ovulation and the beginning of the next menstrual cycle is called the luteal phase. The follicle gets converted to a corpus luteum during this phase. A corpus luteum is the cell structure that produces high amounts of progesterone and some oestrogen. These luteal phase hormones play an important role in pregnancy.

If you have a normal menstrual cycle of about 25 to 28 days, the luteal phase will last for about 12 to 14 days. If you have a menstrual cycle lesser than 25 days, the luteal phase can be shorter.

Can you get pregnant during the luteal phase? Yes, you can. Since the luteal phase is after ovulation, you have a very real chance of getting pregnant.

Why Is the Luteal Phase Important for Pregnancy?

The luteal phase is the period between ovulation and menstruation. Therefore, the health and length of the luteal phase will speak to the regard of your fertility.

1. Impact of the Luteal Phase’s Length On Pregnancy

If your period of luteal phase is less than ten days, then you may find it hard to become pregnant. The reason behind this is that if your corpus luteum weakens and dies in 9 days, ceasing the luteal phase hormone production, then your uterus starts shredding its lining instantaneously, leaving no time for the fertilized ovum to move from the Fallopian tube to the ovary, and get implanted to the uterus lining.

If your luteal phase is short, you will not get pregnant even if the ovum gets fertilized, because you will get your period before the embryo can stick to the uterus lining.

2. Impact of the Luteal Phase’s Health On Pregnancy

Sometimes, even if the duration of the luteal phase is normal, your body may produce less amount of progesterone during this phase, which can be a problem. A sufficient quantity of progesterone is needed to ensure the healthy thickness of the uterus lining. Low amount of progesterone results in a lining that is not healthy enough to sustain a pregnancy.

Therefore, it is important to have a luteal phase that is of normal length and is healthy as well.

How to Calculate Luteal Phase of a Menstrual Cycle

Here are some ways to calculate the length of your luteal phase:

• A hormone-specific blood test can determine the accurate length of your luteal phase.
• You can track your menstrual cycle for approximately 6 months, and observe the patterns of your phases of the menstrual cycle, to calculate an approximate length of the luteal phase.
• Basal Body Temperature (BBT) Charting: The BBT of your body increases during ovulation, and stays high until the onset of your upcoming period. Track the temperature from the starting of the menstrual cycle, and observe the rise in BBT. The rise in body temperature is a solid confirmation that you are ovulating.

Formula to Calculate Ovulation Time During Luteal Phase

• Day of ovulation = length of menstrual cycle – length of luteal phase

Assume that for a menstruation cycle that lasts for 29 days, the luteal phase lasts up to 15 days. Assigning these values in the formula:

• Day of ovulation = 29
• 29 (length of menstrual cycle) – 15 (length of luteal phase)
• Day of ovulation = 14

It implies that the 14th day of the menstrual cycle is the day your ovulation occurs.

A prediction kit or calculator for ovulation can also be used to know the day of ovulation, and hence the luteal phase.

Body Changes in Luteal Phase

During the luteal phase, the upsurge in progesterone levels can result in the following body changes:

• Mood swings
• Tiredness
• Tender nipples and breasts
• Bloating
• Anxiety
• Fluid retention

These changes are bound to happen, and do not lower your likelihood of getting pregnant.

What Causes a Short Luteal Phase?

When your body doesn’t produce sufficient progesterone, your luteal phase might end early. The following reasons might be responsible for not producing enough progesterone:

• Thyroid disorders
• PCOS
• Obesity
• Excessive exercise
• Anorexia (and milder forms of restrictive eating)
• Stress
• Ageing

How Do You Know That Your Luteal Phase Is Short?

You can know that your luteal phase is short by tracking your menstrual cycle. Count the number of days between ovulation and the onset of your next period, and this will give you an idea of the length of your luteal phase.

If your luteal phase lasts for 12 or more days, it is normal. But, if your luteal phase lasts less than 10 days, you have low levels of progesterone level. This means that your luteal phase is short.

How Can You Test Your Progesterone Level?

The luteal phase progesterone levels are generally higher than in other phases of your menstrual cycle. Your progesterone levels should be tested when they are highest, i.e. in the middle of the luteal phase, which is on the 21^st day of a normal 28-day menstrual cycle.

Of course, it is not given that all women have a typical 28-day menstrual cycle. If you have a 34-day menstrual cycle, with ovulation occurring around the 22^nd day, then you cannot test your progesterone level on day 21, as the results might show a very low level of the hormone. But, if you test it on the 28^th day, your progesterone level may be normal.

Hence, if you want to know when you ovulate and the length of your luteal phase, tell your doctor about the right time to test your progesterone levels.

How Can You Increase the Luteal Phase?

Taking the following supplements might help to lengthen your luteal phase:

• Vitamin C – it increases fertility in some cases where women have short luteal phases.
• Progesterone supplementation or cream – Progesterone cream can increase your progesterone levels, but please consult your doctor before using this.

What is a Luteal Phase Defect?

Luteal phase defect or luteal insufficiency is the deficient release of progesterone all through the luteal phase. The insufficiency of progesterone will not thicken the uterus lining, which can result in improper embryo plantation. Hence, it reduces the chances of a pregnancy continuing. However, it is not yet confirmed if a luteal phase defect is a reason for infertility.

A luteal phase defect can lead to the following problems:

• Improper working of corpus luteum, which results in lesser production of estradiol and progesterone.
• Incapability of the uterus lining to react to normal levels of estradiol and progesterone.

1. Cause of Luteal Phase Defect

A luteal phase defect could happen due to the following reasons:

• Defect in the egg
• Breakdown of corpus luteum
• Un-ruptured follicle
• Thyroid disorders
• Over-exercise
• Anorexia
• Endometriosis
• Polycystic ovary syndrome
• Obesity
• Hyperprolactinemia

2. Symptoms of Luteal Phase Defect

The symptoms of a luteal phase defect are as follows:

• Miscarriages
• Spotting in between periods
• Menstrual cycles way earlier than normal

3. Diagnosis of a Luteal Phase Defect

A luteal phase defect can be diagnosed by getting the following tests done:

• Blood tests  

These tests check the level of:

1. Progesterone, which helps in the thickening of the uterus lining.
2. Follicle simulating hormone, which regulates ovarian functions.
3. Luteinizing hormone, which triggers ovulation.

• Ultrasound

It helps to find the thickness of the uterus lining. An ultrasound scan can help detect the functioning of the reproductive organs, i.e. the uterus, ovaries, cervix, and Fallopian tubes.

• Endometrial Biopsy

A small sample of your endometrial lining is procured and examined under a microscope to check its thickness. This should be done at least one or two days before the start of your periods.

4. Treatment Options for Luteal Phase Defect

The treatment of a luteal phase defect depends on the main underlying causes.

• Human Chorionic Gonadotropin: It releases progesterone and triggers ovulation. During this process, the hCG level is given in a single dosage of 10,000 IU or two dosages of 5,000 IU, given once in 2 weeks to extend the luteal phase.

• Clomiphene Citrate: These are also called human menopausal gonadotropins. These help in stimulating the ovaries to produce more follicles, which release more eggs.

• Suppositories: Crinone, a vaginal gel, is used vaginally three times a day. The gel holds a progesterone dosage of 90 mg.

• Pill Treatment: Prometrium oral progesterone medicines are administered at a 200 mg dosage per day.

• Injections: Intramuscular progesterone is administered with a dose of 25 to 50 mg per day. The injection uses crystalline and odourless progesterone powder dissolved in sesame oil.

The luteal phase that lasts around 14 days is the time when the female body prepares the womb for the fertilized ovum. You should have a luteal phase of both sufficient length and health to sustain a pregnancy. You can consult a doctor for mid-luteal phase progesterone test to check if everything is normal.

Also Read: LH Surge