Conception

LH surge and ovulation test: how to understand that you are about to ovulate

What is the LH surge and how long does it last? How to spot it with ovulation tests and when to have intercourse to increase the chances of getting pregnant?

When trying to get pregnant , what matters is not only feeling good and being convinced of what you are doing within the couple, but also having intercourse in the fertile days of the menstrual cycle (ie close to ovulation ) .

However, many women do not know when they ovulate or fail to recognize the symptoms of ovulation or have a very irregular cycle, which makes everything even more complicated.

To make things easier, so-called  ovulation tests can be used , which work by detecting the increase of luteinizing hormone in the urine , i.e. the so-called  LH surge .

But be careful: if your periods are very irregular (for example, they skip months) it is important to talk to your gynecologist, because this characteristic may be due to hormonal imbalances which could make the search for pregnancy more complicated.

In fact, there are conditions such as polycystic ovarian syndrome  (PCOS) which involve irregular cycles with increases in the hormone LH in the absence of ovulation which make the use of tests useless .

In this article we will discuss the normal changes in LH during a menstrual cycle (ie the period between the start of one period and the day before the next). Therefore what we will explain below  is not applicable to those with PCOS problems .

LH surge and ovulation

Ovulation  is a complex symphony of events leading to the release of a mature egg cell from the ovary This moment is preceded by an increase in the production of LH , in which the levels of this hormone in the blood begin to rise, reach a maximum peak and then fall within a few hours.

Under normal conditions, the production of LH is very low during the  menstrual cycle . However, once the dominant follicle (which will release the mature egg) reaches a certain size, LH secretion rises to very high levels and it is this increase that triggers ovulation .

LH surge and ovulation

Ovulation  is a complex symphony of events leading to the release of a mature egg cell from the ovary This moment is preceded by an increase in the production of LH , in which the levels of this hormone in the blood begin to rise, reach a maximum peak and then fall within a few hours.

Under normal conditions, the production of LH is very low during the  menstrual cycle . However, once the dominant follicle (which will release the mature egg) reaches a certain size, LH secretion rises to very high levels and it is this increase that triggers ovulation .

Many of the kits recommend testing with the first urine sample of the morning. However, a study of 155 cycles by 35 women showed that the onset of the LH surge occurred mainly between midnight and early morning (37% between 00:00 and 04:00, 48% between 04:00 and 08 :00).

Consequently, since  the LH surge typically begins in the early morning hours, our advice is to test the second morning urine, to reduce the risk of missing the LH surge.

For best success in detecting the LH surge, it is important to test for ovulation at approximately the same time each day and reduce fluid intake for the previous 2-4 hours . In fact, drinking a lot before the test can dilute the LH concentration in the urine and make it difficult to detect the hormone.

What if the ovulation test does not detect the peak?

The LH surge may not be seen in every cycle .

If you have trouble pinpointing your peak with ovulation tests or have very irregular or long cycles, you can ask your gynecologist to run some blood tests (hormonal tests are done between the second and fourth day of your period). These tests can be interpreted correctly by your gynecologist or an endocrinologist who specializes in infertility.

Ovulation can also be monitored through a transvaginal ultrasound performed at pre-established time intervals. This allows your doctor to look at your ovaries and see how the follicles are growing. These are the so-called  ultrasound follicular monitoring  to follow ovulation.

LH surge: when to have intercourse?

Once the egg is released from the ovary, it is fertile for only 12-24 hours and then degenerates. While sperm can survive in a woman’s reproductive tract for up to 3-5 days.

For this reason, it is advisable to have intercourse from the day the LH surge is detected (ie when two marked lines appear on the test) and preferably  every other day . Even better would be to have intercourse  the day before the peak as well , when the second line starts to intensify.

Does the LH surge give me the confidence to ovulate?

No, the LH surge may not always mean true ovulation.

In a study of 43 women, in which urine LH was recorded and analyzed daily, it was found that  LH surges are not of a single type and are extremely variable.

The onset of the urinary LH surge has been classified into two types:

  • rapid onset (within one day, 42.9%)
  • with gradual onset (in 2-6 days, 57.1%).

Additionally, two women (4.3%) showed an LH surge without ovulation .

In infertile women , a premature LH surge that did not trigger ovulation was found in 46.8% of cycles .

In addition, a condition referred to as “unruptured luteinized follicle syndrome” (LUF) has been reported,  occurring in 10.7% of menstrual cycles in normally fertile women. People with this condition have a normal LH surge , functioning corpus luteum, and menstruation, but do not release any eggs .

Although we speak of a syndrome, it is important to underline that LUF can also be only occasional and not recur for all cycles.

LH surge: how long does it last?

As we have already mentioned, the LH surge can have a variable duration, from 1 to 6 days .

Very detailed studies have confirmed the diversity of LH surges in terms of configuration, amplitude and duration. This diversity should be taken into consideration as it would probably benefit the treatment of hormonal causes of infertility.

In particular, two features of the LH surge were found to be associated with the ovulation process:

  • multiple LH surges were associated with smaller preovulatory follicles ;
  • sustained LH surges for more than 3 days after ovulation were associated with delayed luteinization.

Multiple surges could be a symptom of follicular insufficiency, while a sustained LH surge could be a sign of luteal insufficiency. These hypotheses should surely motivate further research.

Dr Kathryn Barlow

Kathryn Barlow is an OB/GYN doctor, which is the medical specialty that deals with the care of women's reproductive health, including pregnancy and childbirth.

Obstetricians provide care to women during pregnancy, labor, and delivery, while gynecologists focus on the health of the female reproductive system, including the ovaries, uterus, vagina, and breasts. OB/GYN doctors are trained to provide medical and surgical care for a wide range of conditions related to women's reproductive health.

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