More often than not, human twins are born within minutes of one another. But sometimes, the delay between baby arrivals can get extended to days, weeks… or even much longer.

通常情况下，双胞胎在几分钟内相继出生。但有时，婴儿出生之间的延迟会延长到几天、几周……甚至更长。

In an extremely rare case in Kazakhstan, a woman gave birth to twins who were born almost three whole months apart – with 11 weeks passing between the births of a baby girl, Liya, on May 24, and her brother Maxim, who eventually turned up this month on August 9.

在哈萨克斯坦的一个极其罕见的案例中，一名妇女生下一对双胞胎，她们几乎相隔了三个月——从5月24日的女婴利亚，到8月9日出生的弟弟马克西姆，相隔了11周。
Thankfully, the health of the mother, 29-year-old Liliya Konovalova, and her two babies is reported to be fine, but the Kazakh Health Ministry, who shared the news of the births on social media, estimates this unusual and rare case was a one-in-50-million chance.

值得庆幸的是，29岁的母亲莉莉亚·科诺瓦洛娃和她的两个孩子的健康状况良好，但在社交媒体上分享出生消息的哈萨克斯坦卫生部估计，这一罕见病例的几率为5000万分之一。

One of the factors behind the incredible time interval between Liya and Maxim's births is that Liya was born very prematurely, weighing just 850 grams when she was born after a gestational period of only 25 weeks.

莉娅和马克西姆出生的时间间隔如此之长，其中一个原因是莉娅早产了，仅25周就出生了，体重只有850克。

By contrast, when Maxim arrived almost three months later, that extra time in the womb saw him delivered with a healthy birth weight of 2.9 kilograms – more than three times heavier than his 'big' sister.

相比之下，当马克西姆在三个月后出生时，他在子宫里多出了2.9公斤的健康出生体重——比他的“大姐”重三倍多。

But Liya's premature arrival is only one part of the story. The fundamental reason explaining the twins vastly different birthdays is that their mother Liliya has an extremely rare anatomical condition called uterus didelphys – a uterine malformation that effectively results in a double uterus.

但莉娅的早产只是故事的一部分。这对双胞胎生日差异如此之大的根本原因是，他们的母亲莉莉亚有一种极其罕见的解剖条件，叫做子宫双螺旋体——一种导致双子宫的子宫畸形。

When this occurs – which is in less than 0.5 percent of American women – each foetus develops separately in its own uterus, but premature births (and other events, including miscarriage) are a common complication stemming from the abnormality.

当这种情况发生时——在不到0.5%的美国妇女中——每个胎儿都在自己的子宫中独立发育，但早产(以及包括流产在内的其他事件)是由这种异常引起的常见并发症。

"My son was in no rush to come out into the world," Liliya told regional media outlets.

“我的儿子并不急于走向世界，”莉莉娅对当地媒体说。

"Thanks to our doctors, we prevailed… what they did is a miracle. My kids now weigh around 3 kilograms and we're getting ready to be discharged from the hospital."

“多亏了我们的医生，我们成功了……他们所做的是一个奇迹。我的孩子大约有3公斤重，我们正准备出院。”

Often, women with uterus didelphys are unaware they have a double uterus, and when they become pregnant, may be unaware that they are in fact pregnant with twins.

通常，有子宫双螺旋体的妇女并不知道她们有双子宫，而她们怀孕时，也可能不知道她们实际上怀了双胞胎。

Such was the case for a Bangladeshi woman with the condition who gave birth to twins 26 days apart earlier in the year, and whose doctor said he had never "seen any case like this in my 30-year plus medical career".

今年早些时候，一名患有此病的孟加拉国妇女产下了一对相隔26天的双胞胎，她的医生说，“在我30多年的医疗生涯中，从未见过这样的病例”。