大姨妈在的时候能不能怀孕

It's a question we've all probably asked ourselves, and one we thought there was a definite answer to: can you get pregnant on your period? Well, the answer is yes - but it's very unlikely, so hear us out.
我们可能都问过自己这个问题，我们也认为这个问题的答案十分肯定：经期能怀孕吗？答案是：能--但可能性不大，请听我为您娓娓道来。

First, it's important to understand how the monthly cycle works. Menstruation is in essence the shedding of the endometrium, which is the inner lining of the uterus. On the first day of your period, hormone levels drop and menstrual blood flows from the uterus through the small opening in the cervix, shedding the tissue lining. Around day 14 of the monthly menstrual cycle, hormones cause a mature follicle in the ovaries to burst, then release an egg from the ovary (ovulation). The egg travels down the Fallopian tube toward the uterus - a sperm can unite with an egg here, fertilising it. However, if the egg is not fertilised, the egg breaks apart and is shed during the period, which occurs back around day one of the cycle.
首先，理解经期的运作方式是非常重要的。本质上，月经是子宫内膜的脱落。大姨妈来的第一天，激素水平下降，姨妈血从子宫流向子宫颈的小开口，使得组织内膜脱落。经期周期的第14天左右，激素使得卵巢中的成熟卵泡破裂，导致卵巢排卵。卵子从输卵管向下移动到子宫--精子可在此与卵子结合、受精。然而，如果没有受精，卵子就会分裂，在经期脱落，这一情况在经期周期的第一天发生。

So can you get pregnant during your period?
所以，大姨妈来的时候究竟能不能怀孕？

The odds of getting pregnant during your period are extremely low, but it can (and has) happened. During your period, the part of the menstrual cycle when the egg is released and therefore has the potential to unite with a sperm (aka ovulation) is still several days away. But there are exceptions. According to the American Pregnancy Association, "If you happen to be one of the individuals who has a shorter cycle, there is a chance you could get pregnant while having sex during your period."
经期怀孕的可能性非常低，但的确是有可能发生的（而且也的确发生过）。大姨妈期间，排卵并有可能与精子结合的月经周期部分可能还要过几天才会发生。但也有意外。据美国怀孕协会表示，"如果你的经期较短，那在经期发生性关系就有可能使你怀孕。"

This means that the time between your period and your ovulation is closer together. Sperm can live inside of you for up to five days after it is released, so if you have sex toward the end of your period, it would hypothetically be possible to conceive four or five days later with your early ovulation. "The probabilities of getting pregnant while on your period are low, but the possibilities are there," says the APA.
这就意味着你的经期和排卵期相近。精子排出后能够在你身体内存活长达5天的时间，所以如果你在经期快要结束时发生性关系，理论上而言，这些精子可以与四五天后较早排出的卵子结合。"经期怀孕的可能性很低，但还是可能的，"美国怀孕协会的人员说道。

What about right before or right after your period?
那经期前或经期后呢？

As mentioned above, the time after your period is when preovulation and ovulation begins and hormones increase. This means you are most fertile between day 11 and day 21 (approximately) of your menstrual cycle, says the American Pregnancy Association.
如上所述，经期结束之时正是排卵前和排卵开始以及激素增加之时。这就意味着在你经期的第11天和第21天（大约）之间你是最容易受孕的，美国怀孕协会表示。