Since it is difficult for every mother-to-be to determine the exact time of conception, the medical rule is to calculate the due date from the first day of the last menstrual period, whose entire pregnancy lasts for a total of 280 days and 10 gestational months (each gestational month is 28 days). Do you have to ask your doctor to predict your due date? In fact, there are several ways for pregnant mothers to predict the due date by themselves. 1.Calculation according to the last menstruation Medically, the due date is calculated from the first day of the last menstruation, and the whole pregnancy period is 280 days, 10 gestation months (28 days for each gestation month). 28 days is the menstrual cycle = the first day of the last menstrual period + 280 days (then extrapolated by the actual number of days per month). For example, if the first day of the last menstrual period was August 10, 2006, then the expected date of delivery would be May 17, 2007. There is also the simpler Nigel’s rule: for months ≥ 4, due date = month – 3, date + 7; for months ≤ 3, due date = month + 9, date + 7. In addition, those with a menstrual cycle other than 28 days must be corrected. For example, if 30 days is the date of the menstrual cycle and then +2, and the last menstruation is January 10, 2012, then the due date is October 19, 2013. Set formula month = 1 + 9, day = 10 + 7 + 2. Accuracy: 95% This is the method commonly used by obstetricians and gynecologists at present. However, because many pregnant m can’t figure out their menstrual date or their ovulation day is not regular, it can affect their results. On the contrary, if the menstrual date is accurate, this algorithm can be 100% accurate. Difficulty: easy. 2.According to the date of early pregnancy reaction Early pregnancy reaction refers to a series of reactions such as dizziness, weakness, loss of appetite, preference for acidic food or aversion to greasy food, nausea, morning sickness and vomiting during the early stage of pregnancy (about six weeks after menopause), when the chorionic gonadotropin (HCG) in the mother-to-be’s body increases, and the secretion of gastric acid decreases and the gastric emptying time is prolonged. Around the 6th week of pregnancy, the mother-to-be may start to feel a series of reactions such as nausea and vomiting, headache, fatigue, loss of appetite and breast tenderness. These pre-pregnancy symptoms are collectively known as early pregnancy reactions. These symptoms usually do not require special treatment. After 3 months of pregnancy, with the decrease of HCG level in the body, the symptoms will disappear naturally and the appetite will return to normal. Therefore, the expected date of delivery can be calculated based on early pregnancy reactions. Reactive vomiting usually occurs at the end of the 6th week of pregnancy, which is 42 days after the last menstruation, and the expected date of delivery is 280 days backward. Calculation formula: Due date = date of onset of early pregnancy reaction + 34 weeks. Accuracy: 58% Because the period of the onset of pregnancy vomiting varies from person to person, it is not an accurate method. Difficulty: more difficult. 3.Calculation according to the date of fetal movement The above method is not reliable for those who have unclear or irregular menstruation, and the method according to the date of fetal movement can be used to calculate the due date. First find out the date of the first fetal movement, and then calculate according to the number of weeks. For mothers who have given birth for the first time, add twenty-two weeks (for mothers who have given birth for the first time) or twenty-four weeks (for mothers who have already given birth) to the date when the mother feels the first fetal movement. For mothers who have given birth for the first time, the fetal movement is usually felt after 18 weeks, and for mothers who have already given birth, the fetal movement is usually felt after 16 weeks, but this method is less reliable. The purpose of calculating the due date is not to determine the actual date of delivery. In addition, it is the first time to give birth also affects the number of weeks of fetal movement feeling, usually the first time the mother-to-be feels the fetal movement in the 20th week; while the mother-to-be is in the 18th week. Accuracy: 58% Fewer people use this as the only algorithm for their due date, because some mothers-to-be have obvious fetal movements and some do not, and it is difficult to determine whether it is the first time or not. Difficulty: difficult. Lastly, if you want to predict your due date accurately, you can use ultrasound to do so, which is highly accurate and easy to predict. The gestational age can be estimated and the expected date of delivery can be projected by measuring the inter-parietal diameter of the fetal head, the head-rump length and the femur length during the ultrasound performed by the doctor (this method is mostly used as a diagnostic application for the ultrasound examination by the doctor). If you suspect that you are pregnant, the best way is to go to the obstetrics and gynecology department for a checkup as soon as possible. If the “heartbeat and embryo” can be detected, then it means 7 weeks of pregnancy. Accuracy: 98% This is the most accurate way to determine the due date in medicine, but it is limited by the care of the physician who performs the ultrasound examination and whether the examination angle is maximized. Difficulty: Very easy.