Normal basal temperature in pregnancy: chart

The menstrual cycle of the fair sex, which lasts on average 28-35 days, can be divided into 2 phases: pre- and post-ovulation. In the first phase of the sexual cycle, a healthy woman usually does not experience alarming temperature fluctuations. In her ovaries, under the influence of estrogens, eggs gradually mature (usually 1 per month), which is not accompanied by a rise in temperature. On the contrary, in the first days of menstruation, a slight decrease may be observed, but throughout the first phase, basal temperature fluctuations remain within 36.1 - 36.8 degrees. If it becomes higher, this indicates either inflammation in the reproductive system or a deficiency of estrogens, which, as we know, reduce the body's temperature.

If you follow the basal temperature chart during the first phase of the female cycle when planning a pregnancy, you can see how it gradually decreases during the first week, which indicates an increase in the production of estrogens necessary for the maturation of the egg, and a decrease in the synthesis of progesterone. To some, this point may seem insignificant, because pregnancy is judged by the second phase of the cycle, which is what is paid more attention to. In fact, by changes in the temperature of the first phase, you can already judge the functioning of the endocrine system and, in particular, the sex glands. With a lack of estrogen (temperature above 36.8 degrees), the egg may simply not mature, and waiting for pregnancy in this case is useless, although the problem is usually solved by simply introducing substitutes for the female hormone.

When the egg is mature and ready to come out, the day before ovulation or on the same day, the woman's body temperature noticeably drops to 36 - 36.2 degrees (the reason lies in the same estrogens, which are released in maximum quantities during this period). After the egg leaves the follicle, the need for increased estrogen production decreases, but the need to maintain a possible pregnancy appears. The corpus luteum appears at the site of the ruptured follicle, and the synthesis of progesterone begins, which at this stage is more important for maintaining a possible pregnancy. This causes a consistent increase in the temperature of the body's tissues during the second phase of the menstrual cycle up to the 21-25th day, after which it either falls (if conception has not occurred) or remains elevated (if pregnancy occurs). [ 1 ]

There is no need to be afraid of the rise in basal temperature in the second phase when planning a pregnancy. This is a normal physiologically conditioned process, and the difference in temperatures is not that high. The interval between the highest temperature of the first phase of the cycle and the maximum thermometer reading in the second is usually 0.4-0.5 degrees.

The pre-ovulatory drop in temperature after the rupture of the follicle is accompanied by a sharp increase (the fact is that before the appearance of the corpus luteum, progesterone is synthesized and accumulated in the follicle, and after its rupture it is released into the blood, which causes a sharp jump in temperature, although on the first day it rarely rises to 37 degrees). It is this jump in temperature in the middle of the cycle that women who want to get pregnant should pay attention to, because it indicates ovulation and the optimal opportunity to become a mother.

Subsequently, thanks to the luteinizing hormone that enters the bloodstream on the eve of ovulation, the corpus luteum is formed, which, as it develops, increases the concentration of progesterone in the blood, which means that the temperature continues to rise, reaching values of 37.1 - 37.2 degrees (sometimes up to 37.7, which is not considered a pathology if it does not last too long).

After 21 days of the cycle, in the absence of fusion of the egg and sperm, the gland, called the corpus luteum for its color, becomes unnecessary, it gradually atrophies and is excreted from the body during menstruation. During this period, a gradual decrease in progesterone production is observed and, accordingly, a decrease in body temperature even before the onset of phase 1 of the next menstrual cycle.

If conception has occurred, the gland actively functions for another 2.5-3 months, and sometimes longer, thereby preventing miscarriage. Ask doctors what the basal temperature should be during pregnancy, and they will not give a specific answer, because a temperature of 37.1 degrees is considered normal, and a couple of tenths of a degree more - 37.2-37.4.

In many ways, these indicators depend on the individual characteristics of the body of the expectant mother, the activity of the processes occurring in it, because even in the absence of hormonal changes associated with pregnancy, the body temperature of different people at rest can differ by 0.1-1 degree. It is not surprising that potential mothers can have an individual temperature, and if it does not deviate from the norm by more than 0.8-1 degree, there is no reason to worry.

If the basal temperature after conception of a child does not coincide with the norm (the generally accepted norm is considered to be a temperature of 37.1-37.3 degrees), do not worry in vain, because the individual norm can only be determined in comparison with the usual temperature. For example, if in the 1st phase of the cycle a woman's temperature did not rise above 36.5 degrees, then in the 2nd phase it is unlikely to be above 37.

It should be noted that it makes sense to talk about what the basal temperature during pregnancy should be in the morning after waking up; it is not logical to measure it in the evening, because the body spends energy during the day, is exposed to internal and external factors, so the measurement results will not be adequate. Advice to measure basal temperature during pregnancy twice a day has no logical basis. Evening measurements will differ both from morning ones and from each other, regardless of how the pregnancy is progressing. [ 2 ]

Basal temperature and pregnancy

Measuring basal temperature is considered an accessible and quite effective method of diagnosing pregnancy, which allows you to detect it from the very first days without additional instrumental and laboratory studies. Usually, a woman learns about the onset of pregnancy by the absence of menstruation at the appointed time and several days after its planned onset.

Basal temperature, if measured regularly, allows you to find out about pregnancy even before a delay. After all, most often the interval between conception and the beginning of the next period is about 14-16 days, during which the egg has time to undergo several divisions, change its place of residence and gain a foothold in the uterus. During this period, the future child's nervous system and some organs are formed, even if he still does not look much like a person, he will definitely become one with the help of his mother.

Until the placenta forms around the embryo, which later becomes an embryo, the corpus luteum will be responsible for its preservation, producing progesterone in sufficient quantities. This hormone prepares the uterus for the introduction of the fertilized egg on the eve of implantation, then restrains its excessive activity and premature contractions, prevents the rejection of the embryo as a result of incorrect work of the main defender of the body - the immune system, which considered it a foreign body. Progesterone also promotes the production of other hormones that are considered important for the normal development of the fetus. maintaining pregnancy and preventing premature birth. [ 3 ]

It is not surprising that during pregnancy the basal temperature has higher values both at the onset of pregnancy and in its early stages. How to understand that conception was normal, and there is no need to worry about the level of progesterone? Again, by body temperature at rest. Its values during the first month should correspond to those that were established during the week after the day of ovulation. This temperature usually lasts until the period of placentation (the end of the 2nd month of pregnancy), and then gradually returns to the normal norm. Although in most cases it remains slightly elevated (within 37 degrees), because the secretion of progesterone in the body of a pregnant woman continues, but this function after 12-14 weeks from the beginning of conception is already performed by the placenta.

The beginning of placental secretion of progesterone again causes an increase in its level in the woman's body, because the larger the child becomes, the more difficult it is to restrain the activity of the uterus. But the body of the expectant mother no longer reacts so sharply to changes in hormonal levels. It develops a certain resistance to progesterone surges, so there is no noticeable increase in temperature until the end of pregnancy, although the concentration of the hormone increases 8-10 times during this time. It decreases sharply only before childbirth, which allows the uterus to actively contract. [ 4 ]

Basal temperature chart

Speaking about the norm of basal temperature during pregnancy, we noted that not all deviations from the generally accepted norm are considered pathology. Body temperature is an individual matter. Progesterone can change it slightly, based on stable readings for each individual.

It is easy to determine your basal temperature norm by measuring it daily after sleep in the middle of the first phase of the cycle. You need to be prepared for the fact that even in a relatively calm time, when the follicles mature with the participation of follicular progesterone and estrogens, there will be fluctuations in the thermometer readings, which is an indicator of the stability of estrogen production. Such fluctuations within 0.5 degrees are quite normal, but what should you base your calculations on when calculating the basal temperature norm?

As a starting point, we take the average indicator, which will reflect our true norm, or the maximum and minimum indicators, by which we can immediately determine both the lower and upper limits of the norm.

In principle, whether to make a basal temperature chart when planning a pregnancy by days, weeks, months or simply keep a diary, recording the results of regular measurements, is an individual matter. But such records and charts help to track the dynamics of temperature indicators, calculate the moment of its maximum drop, followed by a sharp increase in values, which indicates ovulation and a good chance of conceiving a child, effectively protect yourself if having a child is not yet in the plans of a woman and her partner. It is not surprising that doctors for diagnostic purposes still insist on making a chart (temperature curve), which is subsequently easier to decipher due to the clarity of the results and their changes. [ 5 ]

Gynecologists distinguish the following types of temperature curves, by which one can judge the presence of various disorders in the reproductive system and hormonal deviations:

• The norm for a two-phase menstrual cycle is considered to be a difference of 0.4 degrees in basal temperature in phases 1 and 2 of the cycle. In this case, doctors compare thermometer readings at the moment of temperature drop before menstruation and before ovulation. In the post-ovulation period, a jump in temperature is observed, after which its values remain at a relatively high level for 12-14 days.
• If the temperature rise in the second phase is weaker (0.2-0.3 degrees), i.e. the temperature fluctuations are insignificant, this may indicate insufficient production of sex hormones: estrogens and progestin. A low rate of temperature rise after ovulation indicates that the follicle did not rupture, i.e. there was no ovulation, the egg in it did not mature.
• When the temperature rises shortly before the onset of menstruation, i.e. at the end of the 2nd phase of the cycle and does not fall on the eve of menstruation, while the second phase of the cycle is unusually short (less than 10 days), we can talk about the same two-phase cycle, but with insufficiency of the second phase (luteal). In other words, we are talking about disturbances in the formation and functioning of the corpus luteum, i.e. progesterone deficiency, as a result of which the fertilized egg is not able to normally attach to the uterus. This causes spontaneous miscarriages in the earliest stages of pregnancy.
• If the temperature curve does not show a temperature difference in two phases of the cycle (monotonic curve), i.e. there are no noticeable temperature fluctuations in the middle of the menstrual cycle, we speak of an anovulatory (single-phase) cycle. In such women, menstrual bleeding may occur regularly, which is perceived as the absence of any pathology. In principle, this is true if we are talking about teenage girls during the period of establishing menstruation, pregnant women and nursing mothers.

There are unusual cycles without maturation and release of the egg in mature healthy women due to stress, strict diets, lack of sleep, intoxication, some somatic diseases, hormonal changes (menopause). It is considered a pathology if such cycles become regular.

Menstrual cycles without ovulation, which become systematic, can cause infertility. They arise as a result of disruption of the production of female and male hormones in the woman's body, genetic mutations, polycystic ovary disease, disruption of their functionality, and some other pathologies of the reproductive system.

Symptoms of an anovulatory cycle may include delays, shifts, absence of menstruation, excessive bleeding during menstruation, etc. This allows you to suspect a pathology and consult a doctor in time. However, in some cases, no changes in the time and nature of menstruation are observed, and a woman may suspect a disorder only based on multiple futile attempts to become pregnant. It is possible to determine whether ovulation is occurring, i.e. the maturation and release of an egg from the follicle, without which conception of a new life is impossible, using a graph that shows changes in basal temperature during the cycle, or better yet, over several cycles. [ 6 ]

• Some women have such an individual temperature curve that it does not fit into any of the above types. Most often, these are random changes and temperature jumps throughout the menstrual cycle. Unlike a single-phase cycle, the graph shows a pre-ovulatory drop and the following jump in temperature in the middle of the cycle, and in other periods, the temperature can fluctuate significantly by day.

In such a situation, the doctor may suspect estrogen deficiency, which results in a lack of temperature balance. In the second phase of the cycle, such women may experience temperature jumps above normal, i.e. up to 37.6-38 degrees in the absence of infectious and inflammatory pathologies.

Drawing up a basal temperature chart during pregnancy or planning it is a responsible matter. For clarity, after plotting the points on the chart, one axis of which reflects temperature changes with an interval of 0.1 degrees, and the second counts the days of the menstrual cycle with a step of 1 day, you need to draw 2 lines: the middle (horizontal) and the ovulation line (vertical). We draw the middle line as follows: we discard the readings of the first 5 days of the cycle and draw a line based on the matching temperature readings of the next 6 days. We draw the ovulation line, retreating a couple of cells to the right of the pre-ovulatory decrease in temperature.

All this can be easily done on a normal chart, when the onset of ovulation is easy to predict (the middle of the cycle, if its duration is known), and we are talking about measuring temperature when planning a pregnancy or to increase the effectiveness of contraception. Hormonal imbalances in the body tend to change the temperature curve, which complicates its interpretation and requires consultation with a specialist.