双胞胎同母异父？A pair of Vietnamese fraternal twins have been confirmed to have different fathers, a local genetic association has told the BBC.
一对越南的异卵双胞胎已被证实来自不同的父亲，一家当地遗传机构告诉BBC。
The twins had their DNA tested after their family noticed they looked different, said local reports.
该双胞胎在其家庭觉察他们长相不同后，接受了DNA测试，据当地报道。
The occurrence, known as heteropaternal superfecundation, is rare with few publicly known about.
发生的该案例被称为异父超级受精，是鲜为公众所知的罕见案例。
It happens when a woman’s eggs are fertilised by two men within a short period of time.
当一个女性的卵子在短时间内被两个男性受精则会发生。
Professor Le Dinh Luong, president of the Hanoi-based Vietnam Genetic Association which did the DNA testing, said the results were "100% correct" in what he called "an extremely rare case".
总部位于河内的越南遗传协会负责了该DNA测试，其董事长Le Dinh Luong教授称这个“极为罕见的案例”的测试结果“百分百正确”。
"There are only less than 10 known cases of twins with different fathers in the world. There might be other cases but the parents and/or the twins were not aware of it or didn’t want to announce it," he told the BBC’s Nga Pham.
“世界上仅有不到10个拥有不同父亲的双胞胎案例。可能存在有其他案例，但其父母和／或双胞胎并没有意识到或者不想公布，”他告诉BBC的记者Nga Pham。
He declined to give further details citing client confidentiality, but added that local reports stating the twins’ location, names and timeframe were inaccurate.
他拒绝进一步提供引用客户隐私的细节，但补充说当地报道公布双胞胎的地址、姓名和时间框架是不恰当的。
Vietnamese news outlets began reporting on the case earlier this month, saying that relatives had noticed that one of the twins looked markedly different from its sibling and parents.
越南新闻渠道在本月初就开始报道该案例，称亲戚觉察到其中一个双胞胎和另外一个以及其父母很不像。
What is heteropaternal superfecundation?
什么是异父超级受精？
Superfecundation’ refers to the fertilisation of multiple eggs from separate acts of intercourse, and ’heteropaternal’ means they are fertilised by more than one father.
“异父”指的是多个卵子的受精来自于不同的性交，而“超级受精”意思是它们被多于一个父亲受精。
It can happen when a woman produces multiple eggs in one ovulation period and they are fertilised by different men within a few days.
当一个女性在同一个排卵期产生多个卵子并在几天内被不同的男性受精就会发生。
It can also happen if a woman ovulates twice within a short period of time and both eggs are fertilised by different men.
如果一个女性在短时期内两次排卵而两个卵子被不同的男性受精也可发生。
Reported cases are very rare - the last case was in 2015 involving twin girls in New Jersey, only the third such case to ever occur in the US.
被报道的案例极少——上一个案例是2015年新泽西州的两个双胞胎女孩，这是美国发生的第三个案例。
Turkish media reported a similar case in 2010 involving twin boys
土耳其媒体也报道过2010年的一对双胞胎男孩的类似案例。
