There are several ways to track monthly LH surges. In this article, we describe methods of tracking, how long surges last, and how to use them to increase the odds of pregnancy.

The LH surge signals that ovulation is about to start. Ovulation is the medical term for an ovary releasing a mature egg. Levels of LH are low for most of the monthly menstrual cycle. However, around the middle of the cycle, when the developing egg reaches a certain size, LH levels surge to become very high. A woman is most fertile around this time. People refer to this interval as the fertile window or fertile period.

If there are no complications affecting fertility, having sex several times within the fertile period may be enough to conceive. The LH surge begins around 36 hours before ovulation.

Once the egg is released, it survives for about 24 hours, after which time the fertile window is over. Because the period of fertility is so short, it is important to keep track of it when trying to conceive, and noting the timing of the LH surge can help.

It is best to start testing levels when the fertile window is drawing near, or a handful of days before ovulation. Most people ovulate between 7 and 19 days before their next period begins. The egg develops within a part of the ovary called the follicle a fluid filled sac.

As the egg gets ready to ovulate the follicle grows larger. Follicle growth can be measured with ultrasound, a technique which uses sound waves to produce an image on a monitor screen using a tampon-like probe placed in the vagina.

Before ovulation, the follicle is thin-walled and filled with fluid. Ovulation generally happens when the follicle measures between 1. For women having treatment for fertility, ultrasound may help time intercourse or insemination. In women taking fertility drugs, ultrasound may be done on several different days during the menstrual cycle to measure and monitor each follicle. Daily measurement of basal body temperature can help determine if ovulation has occurred.

Women collected daily first morning urine for hormonal assessment and underwent serial ovarian ultrasound. This is a secondary analysis of cycles. The sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios were estimated for varying ranges of LH thresholds.

Receiver operating characteristic curves and cost—benefit ratios were used to estimate the best thresholds to predict ovulation.

Testing earlier in the cycle increases the predictive value of the test. However, prediction by LH testing alone may be affected negatively by several confounding factors so LH testing alone should not be used to define the end of the fertile window.

Complementary markers should be further investigated to predict ovulation and identify the fertile window. The use of the peak cervical mucus along with an LH test may provide a higher specificity and predictive value than either of them alone. Commercially affordable urinary ovulation predictor tests have become commonly used by those women wanting to become pregnant since they were first introduced in the s 1.

In addition, they could also be used as an adjunct to Fertility Awareness Methods 2. These rapid one-step home urinary tests attempt to predict when ovulation is about to occur by measuring the luteinizing hormone LH surge 3.

The rise in LH in the urine is known to occur near the time when ovulation takes place during the menstrual cycle 4 — 6 and may not be strictly one or two days before ovulation as it was first supposed.

However, as also pointed out by these studies, the LH peak is rather best described as a wave than as a peak with its surge occurring prior to ovulation; yet, LH levels may remain high after ovulation during the luteinization process. All of these factors may affect how these tests are interpreted by the user in relation to the day of ovulation.

Some studies have evaluated the validity of these tests 7 — 9 ; however, there is no published evidence indicating which urinary LH concentration level may be ideal to correlate with ovulation. As a result, there is no consensus among the different manufacturers on which threshold to use. Patients were recruited from to from eight natural family planning clinics in France, Italy, Germany, Belgium, and Spain as previously reported A database of information was created but due to legal—commercial disclosure agreements with the funding company Quidel Corporation , the results could not be published until now.

A total of women were finally included, contributing an average of three cycles. The study examined cycles that have been analyzed in other studies Height and weight were measured and body mass index BMI calculated. Each of the participants gave their written informed consent, and the study procedures were carried out in accordance with the Ethical Standards for Human Experimentation established by the Declaration of Helsinki. Each hormonal sample was repeated twice: the relative difference i.

These data remain within the property of the funding company. Serial transvaginal ovarian ultrasounds with follicle measurement were performed by a single physician per center. Ovarian scanning started on the first day women observed cervical mucus or when an LH surge was detected by LH home tests Quidel Corp. Details regarding ultrasound investigations were previously published A positive LH test was defined as a test result above a defined concentration threshold. A negative LH test was defined as a test result below that threshold.

We analyzed only ovulatory cycles as the purpose was to assess the best threshold for LH to predict ovulation. Prevalence P of ovulation across the menstrual cycle was defined as proportion of cycles having an ovulation on a given day. Two core analyses were performed: first the use of any threshold across menstrual cycle and, second, an analysis to identify the performance of a given threshold on a specific day of the cycle. We made use of a decision analysis approach cost—benefit ratio to further assess all the proposed thresholds 13 , Ideally, an optimal choice treats the benefit of true identification of ovulation with a positive test, the same as true rejection of ovulation with a negative test, i.

For example, a lower threshold would give more true positives, but at the cost of more false positives. We additionally tested two hypotheses. The first was whether a given threshold can confirm the end of the fertile window, i.

The second hypothesis was whether the addition of peak-type cervical mucus to a positive LH test would increase its predictive value Score 4 type mucus was defined as peak-fertility type mucus.

Finally, in order to verify the stability of the quality of the LH test for different populations, We carried out a multivariate regression analysis on five co-variables Age, BMI, past use of oral contraception, sport activity, and current smoking to investigate its impact on LH levels during the window of LH testing, i.

This regression was a mixed linear regression to take account of 1 the daily repetition of LH measurements, 2 days being clustered within cycles, and 3 cycles being clustered within women.

The paper argued that the duration of the LH surge varies substantially both within and between women. Additionally, ovulation can occur at the beginning of, during, or after the LH surge. Depending on the length of your personal LH surge, as well as how long it takes your ovaries to respond to the LH signal, a positive LH test might mean that you will ovulate soon, are ovulating right now, or even that you ovulated yesterday and are no longer fertile.

On average, ovulation occurs 24 hours after the first positive ovulation test. That means that you could have several days of positive tests in a row, but already ovulate after the first day. The LH surge only occurs about 24 hours before ovulation. And not all women ovulate 24 hours after the LH surge. Some women ovulate sooner than that, and others ovulate later.

Some women continue to test positive for three days after a positive ovulation test. The length of the LH surge is highly variable from woman to woman. And the actual length of the LH surge does not determine your fertile window.

A study in the journal Fertility and Sterility looked at how long the LH surge lasts in normally ovulating women. The image below represents what different LH patterns would look like on daily LH tests from cycle day 11 through cycle day 21 according to the results of the study:. As you can see from this chart, some LH surges are long, and others are short. In the typical cycle, LH starts out low, then rapidly rises and peaks a day or two before ovulation, then falls back down right after ovulation.

But just as not every woman has a textbook day cycle, not every woman has exactly the same LH curve. The LH surge itself does not have any physical symptoms.