How can women's bodies withstand losing so much blood every month?

Some time ago, a video demonstrating the amount of menstrual bleeding became a hot topic. Many people were confused. Is this the normal amount of menstrual bleeding? It seems that when the amount is heavy, a sanitary napkin can have this much! Some people were also shocked after seeing the back. The maximum amount of blood donation is 400ml, and it can only be donated once every six months. How can women bear so much blood every month?

Image source: Weibo screenshot

The reason for the confusion is that "menstrual bleeding" and "menstrual volume" are actually two concepts, and when menstrual bleeding reaches a certain level, it does pose a risk to health or even life.

What is menstruation?

Just like the surface of the body is covered with skin, the inner wall of the uterus is also covered with endometrium. The skin is divided into dermis and epidermis, and the endometrium is also divided into two layers, called basal layer and functional layer. The basal layer of endometrium is similar to the dermis, located at the bottom, and can produce the surface functional layer of endometrium; the functional layer of endometrium is similar to the epidermis, contains rich glands and small blood vessels, and is regulated by hormones.

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In each menstrual cycle, the basal endometrium will grow a new functional endometrium, so that if a fertilized egg is formed, the early embryo can be implanted in the endometrium, which is rich in blood supply and nutrients. If there is no fertilization, the functional endometrium will shrink and fall off periodically as hormones decrease. Since there are many small blood vessels and glands in the functional endometrium, the shedding process will also be accompanied by bleeding, tissue fluid exudation, etc. These blood, tissue fluid and endometrium mixed together are menstruation.

So you see, "menstrual bleeding" only refers to the amount of blood in menstruation, while "menstrual volume" refers to the total amount of blood, tissue fluid, and endometrium, so the menstrual volume must be more than the menstrual bleeding. In the past, normal menstrual bleeding was defined as ≤80ml per month in clinical practice, but because tissue fluid and endometrial fragments account for more than half of the menstrual volume, the menstrual volume is at least twice the amount of bleeding. You don't have to worry about whether your menstrual volume is too much when you see that your menstrual volume is greater than 80ml every time.

How to determine whether the menstrual flow is excessive?

We first need to reach a consensus: when discussing "menstrual volume", we mean the total amount of menstruation during the entire menstrual period. As long as the total bleeding volume is within the normal range, a sudden burst of rapid bleeding does not mean excessive menstruation, and less bleeding in the last few days of the menstrual period does not mean less menstruation. This is because menstrual bleeding is not a uniform process.

As mentioned above, menstruation is essentially the shedding of the endometrium. If you have ever had a large skin scrape or burn, you will notice that the scabs and dandruff on the wound are concentrated in a period of time, but the scabs and dandruff fall off sporadically during those two days. The same is true for the shedding of the endometrium.

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When the endometrium is shed, the small blood vessels inserted into it break, and this is when the bleeding is the most and fastest, just like when we are just injured. But soon, the blood vessel stumps on the wound surface will shrink and stop bleeding, leaving only a small amount of blood and tissue fluid oozing out, just like every time a small wound stops bleeding automatically.

Therefore, menstruation is always light at the beginning (the endometrium has just started to be shed), then goes through a day or two of heavy bleeding (the endometrium is being shed, bleeding in bursts), and finally light bleeding until it stops (most of the endometrium has been shed, and a small amount remains to be discharged gradually. The wound of endometrial exfoliation repairs itself and stops bleeding).

Because the vagina is normally closed, some menstrual blood can accumulate in the uterine cavity or deep vagina when sitting or lying for a long time. Therefore, a warm current after a sudden activity or a change in body position does not mean that the bleeding has increased suddenly, but that the menstrual blood accumulated during the period of inactivity is discharged at once. This is why appropriate light physical activity during menstruation can promote the discharge of menstrual blood and help the body recover faster.

So, since these are all normal phenomena of menstruation, under what circumstances should we be alert to excessive menstruation?

(Image source: Reference [3])

But as mentioned above, the amount of menstruation is not equal to the amount of blood loss. More than half of the menstrual blood is tissue fluid and endometrium, so judging the amount of menstruation by yourself can only be a rough estimate, and the result is not accurate. Clinically, there is an alkaline hemoglobin method that can accurately determine the amount of menstrual bleeding, but this method is troublesome and expensive, and most people do not need to use this method.

Therefore, we provide a simpler and rougher way of judgment: if the menstrual flow suddenly increases significantly than usual, or there are large blood clots in the menstrual period, the sanitary napkin or tampon is soaked in less than two hours, and the sanitary napkin needs to be changed at night, or if symptoms of anemia such as dizziness and fatigue occur, you need to be alert to the amount of menstrual bleeding and seek medical attention in time to find out the cause of excessive bleeding and correct the anemia in time.

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The most direct harm of heavy menstrual flow is blood loss. Severe and immediate blood loss may lead to shock or even life-threatening. Long-term excessive blood loss can easily lead to iron deficiency anemia. Therefore, if a menstrual woman is found to have iron deficiency anemia during a physical examination, it is important to find out whether she has heavy menstrual flow, insufficient iron intake, etc.

On the other hand, if you see content online discussing menstrual volume and worry that your menstrual volume is too heavy, but a checkup finds that you do not have iron deficiency anemia, it means that the amount of blood loss during menstruation is completely within the body's tolerance range and is normal, so there is no need to worry.

Excessive menstrual bleeding may not just be a menstrual problem

Menstruation is the result of many complex processes in the body, so if menstruation is abnormal, it is often not just a simple menstrual abnormality, but an indicator that there is a bug in a certain program of the body.

For example, the topic of this article: menorrhagia. The reasons behind it may be that hormone disorders cause the endometrium to grow too thick, and local hyperplasia of the endometrium leads to endometrial polyps; it may be that diseases such as uterine fibroids and adenomyosis cause the uterus to be too large and the uterine contraction is abnormal; it may also be that there is something wrong with the blood system, resulting in decreased coagulation function, etc.

Therefore, if you have problems with excessive menstruation, you must go to a regular hospital for timely medical treatment. Not only should you correct anemia, but you should also try to find ways to clarify the causes behind excessive menstruation to avoid delaying the disease.

The reason why I particularly emphasize this point is that under this hot topic, I saw someone mentioned: "I heard that young girls will suffer from anemia, so they don’t care even if their menstrual flow is heavy." This is indeed a very common misunderstanding. Since we are talking about excessive menstruation, let’s talk about iron deficiency anemia.

Iron deficiency anemia

Iron deficiency anemia is essentially a deficiency of iron reserves in the body. Most people suffer from iron deficiency either because of excessive loss or insufficient intake. A few people are unable to use the iron they consume normally due to genetic factors.

Since a certain amount of iron is lost during menstruation every month, many women are iron deficient. The physical development needs of puberty and the loss during childbearing further aggravate the iron deficiency problem of some women.

Iron deficiency patients sometimes have no obvious symptoms, or no typical, specific symptoms corresponding only to anemia, which makes many people ignore or underestimate the harm of iron deficiency anemia. But iron deficiency anemia is not as "mild" as it seems.

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Iron is an important component of hemoglobin. Iron deficiency anemia means that the red blood cells are less able to transport oxygen, which means that the body is more susceptible to hypoxia than normal. In adults, people with iron deficiency anemia are more likely to feel tired, have reduced endurance for daily activities, and are prone to headaches and dyspnea on exertion.

Iron deficiency anemia can also affect the cognitive function of adolescents, leading to problems such as inattention and memory loss. Long-term severe iron deficiency anemia can also lead to changes in appearance such as dry and rough skin, spoon-shaped nails, and chapped lips, abnormal manifestations such as pica and pagophagia, and cardiovascular system symptoms such as tachycardia and hemodynamic instability.

Therefore, although many people do not find obvious discomfort at the beginning, if they are found to be iron deficient or have progressed to iron deficiency anemia, it is still necessary to find the cause of the iron deficiency and follow the doctor's advice for treatment.

For a long time, people have developed many misconceptions about menstruation due to their lack of understanding of it. Some people stigmatize and demonize menstruation, while others have excessive expectations of menstruation due to fallacies such as "detoxification."

Image source: Weibo screenshot

In my opinion, menstruation is just the monthly shedding of the uterus, and bleeding is just a normal manifestation of it. It is neither mysterious nor dirty, and is no different from the metabolism of any other part of the body. I hope that every friend who has menstruation can have healthy menstruation, and I also hope that menstruation will no longer be shamed and demonized, and every woman can understand and be familiar with this physiological phenomenon, relieve menstrual anxiety, and discover and solve various menstrual problems as soon as possible.

References

[1] Xie Xing, Kong Beihua, Duan Tao (eds.); Lin Zhongqiu, Di Wen, Martin, Cao Yunxia, ​​Qi Hongbo (co-eds.). Obstetrics and Gynecology, 9th edition [M]. Beijing: People's Medical Publishing House, 2018

[2]FraserIS,WarnerP,MarantosPA.Estimatingmenstrualbloodlossinwomenwithnormalandexcessivemenstrualfluidvolume.ObstetGynecol.2001;98(5Pt1):806-814.doi:10.1016/s0029-7844(01)01581-2

[3]WyattKM,DimmockPW,WalkerTJ,O'BrienPM.Determinationoftotalmenstrualbloodloss.FertilSteril.2001;76(1):125-131.doi:10.1016/s0015-0282(01)01847-7

[4]LopezA,CacoubP,MacdougallIC,Peyrin-BirouletL.Irondeficiencyanaemia.Lancet.2016;387(10021):907-916.doi:10.1016/S0140-6736(15)60865-0

[5]BrunerAB,JoffeA,DugganAK,CasellaJF,BrandtJ.Randomisedstudyofcognitiveeffectsofironsupplementationinn on-anaemiciron-deficientadolescentgirls.Lancet.1996;348(9033):992-996.doi:10.1016/S0140-6736(96)02341-0

Author: Doctor Feidao Duanyu

Reviewer: Lan Yibing, deputy chief physician, Department of Obstetrics and Gynecology, Zhejiang University School of Medicine