Do not worry, it's not difficult to determine the term, it is enough to understand that the woman's body has its own rhythm, in which organs such as the ovaries and the uterus operate. Outwardly this process is noticeable in the form of monthly. The moon has always been identified with the female principle, one of the reasons for this is the correct cycle, i.e. the time from the beginning to the end of the monthly period is 28 days and is equal to the length of the lunar cycle.
Historically, the date of birth is calculated from the first day of the last menstruation: 280 days are added to this number, which is ten obstetric months. This happened because in the old days there was not enough knowledge of anatomy to determine the date of ovulation. To simplify arithmetic, you can add 7 to the day (because fertilization is possible on the 7-14 day after ovulation), and from the month taken away 3 (because the pregnancy lasts nine months). Suppose that the last menstruation occurred on December 3, 2006 (03.12.2006), then the birth of the baby is supposed to occur on September 10, 2007 (10.09.2007). If you have a regular cycle that lasts 28-30 days, then you can safely add 14 instead of 7. Or add 40 weeks before the last menstrual period. It is in weeks that obstetricians consider pregnancy. And 40 weeks on average, a normal pregnancy.
Future moms do not always understand this way of counting, especially if they know when exactly the conception occurred. It is believed that the ideal time for conception is the moment of ovulation (the exit of the female ovary eggs and its movement towards the uterus). With a normal cycle of 28 days, ovulation occurs on the 14th day. It is at this time that the probability of fertilizing an egg is the largest. Spermatozoon remains alive for 3-5 days, which means that a woman can become pregnant if the sexual intercourse occurred on the 9th day after the onset of menstruation. That is, 3-5 days after sexual intercourse. Incredible? But a fact! Since the ovum lives only one day, after ovulation, conception after this period is unlikely.
If your cycle is different from the standard, the time for ovulation can be calculated by dividing the length of the cycle by 2. Favorable days for conception of your child - 4 days before ovulation and the day of ovulation itself, and then the probability of conception decreases drastically.
There is another way, besides more precise, how to determine the date of ovulation. This is done by determining the basal temperature. Probably every woman knows about this method. Measurements must be made daily at the same time, you can not get out of bed, and the measurement time should be 10 minutes. Before ovulation, the basal temperature will not exceed 37.0 ° C, and after - exceed by at least 0.2 ° C. The day before the temperature jump (on this day the temperature drops sharply), it just will be the day of ovulation. By measuring the basal temperature for 3 consecutive months, you can accurately predict future ovulation.
Most precisely, the date of birth is determined if you know the time of conception or ovulation. In this case, it is necessary to add not 280, but 266 days - the real term of pregnancy. If your cycle lasts 28 days, then there should not be any difference between the calculations for ovulation and for monthly ones. However, if the cycle is different, deviations in the results are possible. That is, if the cycle is shorter than the standard, then the true date of birth will be later than when calculating monthly, and if the cycle is longer, then, conversely, vice versa.
Today, in order to find out the date of delivery, ultrasound can also be used. The prediction is based on the size of the embryo, and its accuracy depends on how early the ultrasound was done. So, if the study was conducted in the first 12 weeks of pregnancy, then the baby's birth date can be determined to within 1-3 days, and if the ultrasound is done in the second 12 weeks, the accuracy is reduced to 7 days. This is due to the fact that in early pregnancy, the size of the baby changes clearly according to the schedule, and in the last 12 weeks the changes are completely individual, therefore it is almost impossible to make a prediction on them.
There is also a more ancient, and at the same time, quite inaccurate way of determining the term. Its essence lies in determining the time when the young mother first felt the wiggling of the child. There is an opinion that if pregnancy is the first, then the mother will notice it on the 20th week, and if the second, then a little earlier - on the 18th week. In life, everything turns out differently, and the amplitude of the error of such a theory goes up to 4 weeks. The sensitivity of the mother and the activity of the baby are especially individual.
In any case, no matter how you count the date of your birth, they usually do not occur exactly at the time you calculated. A delay of up to three weeks is possible. It is best to recount once more, because most often errors in calculations are a source of concern. But we must remember one important circumstance. A normal pregnancy can last from 38 to 40 weeks. And no matter how you correctly believed, the baby can be born at 38 weeks, and this is two weeks ahead of the expected date of delivery. But still, however much we count and count, only one kid knows when he is ready to be born. Therefore, I recommend simply waiting and enjoying such a beautiful state.