BTW... i dont have your answer but its 28 days not 20! ;)
You could just have a shorter cycle. Some women have a long cycle(over 28days) and some have shorter ones.
A normal period is between 3-7 days with a gap of 15-20 days between periods. It varies from person to person as you may have noticed in the numbers, but if you are afraid your period is not right, you can contact a doctor. If you have just had your first period (or second, third or fourth), it is not unusual that you are not regular or have a "normal" menstruation period yet.
Go to your doctor straight away.
Wow girl, you're lucky! Your period comes about every 30 days? Mine is about every 20 days. I too thought that there was something wrong with my cycle, because it was only every 20 days and not at least 28 like most others', My doctor told me there's nothing to worry about. Every girl's period is different, and especially if you started your period less than two years ago, your cycle can be pretty crazy and can vary a lot. So once again, don't worry. If your period starts in less than about 18 days, or it starts in more than about 36, be sure to see your doctor about it.
If your period comes every 20-21 days and stays for 5 days your cycle length is 25-26 days. That would not be considered irregular if your cycle length is relatively the same each month. You would ovulate roughly between days 11 and 13 of your cycle. Clomid could be a good way to start fertility treatment when you are trying to conceive but it would be advisable to discuss fertility treatment options with your doctor first.
Mice have a gestation period of 20 days. They can have 3-14 babies.
Generally day 14 is prime time. Yours might be between 14-20.
Probably somewhere around New Years Day, but if it is born anytime after about 11 December it will be fine. Prepare for a Cristmas baby.
You would have less than a 3% chance by day twenty.
Typical menstrual sloughing (bleeding) should only last 3-4 days. Some females experience cycles up to 7 days. 20 days is highly unusual. You should consult your doctor.
Nothing at all, it's normal. 28 days is the average menstrual cycle length - everyone is different so not everyone will have a 28 day cycle, also it's normal for cycles to change over time and for there to be a few days variation from one cycle to the next. If you go over 28 days then that simply means that your cycle is longer than the average menstrual cycle. Rather than expecting your periods every 28 days you should determine your own average menstrual cycle length. One menstrual cycle is the number of days from the first day of your period up until your next period, you add all these days together over your last 6 cycles and then devide by 6 to get an average. There are various apps for your phone or web sites that figure out your average menstrual cycle length for you. Take my cycles for example; July 25 (35 day cycle) June 20 (32 day cycle) May 19 (32 day cycle) April 17 (27 day cycle) March 21 (31 day cycle) February 18 (26 day cycle) So my average menstrual cycle is 33 days - as long as my periods fall within 26 to 40 days they are still regular. So you see my cycle is longer than 28 days, and there can be a little variation from one cycle to the next, this is totally normal and healthy.
Safe period is not a continuous period in menstrual cycle. We know a woman is fertile only in the ovulatory period, and infertile in other days. And she can not has sexual intercourse in the menstrual period when she's bleeding. So the days in a menstrual cycle except menstrual period and ovulatory period is safe period. In safe period, a woman could has sexual intercourse and almost no chance to be pregnant. But it is not very reliable method for contraception because we cannot predict the next ovulation time precisely. Now we consider the first bleeding day as the first day of menstrual cycle. The days before the 7th day is very safe for contraception. If a woman stopped bleeding in 5 days, she has 2 days to have sexual intercourse without condom. And the last 4 to 5 days are also very safe. You could choose these days in safe period to avoid pregnancy. I suggest you user some software or online safe period calculator.