If I am not mistaken, when you have identical triplets, they were usually quads, but one embryo did not survive gestation.
In this case one embryo spit and then split again.
WHEN the ultrasound scan showed that his patient was going to have three babies instead of one, Dr Cheng Li Chang's first thought was: 'This can't be, it's so rare. Aiyoh, it's going to be tough!'
Triplets are, in themselves, rare, but 30-year-old Ms Gladys Lim's babies are further up the rarity stakes: They are identical, and were conceived naturally to boot.
Most triplets are the result of fertility treatments, in which two or more fertilised eggs are planted in the womb.
Ms Lim and her husband Joey Chiew's three sons, however, came from a single egg which split into two. One of the two then divided again, to make three babies.
The couple, who have a 16-month-old daughter, were 'shocked and surprised' when told, eight weeks into the pregnancy, that they were expecting triplets. The first scan just two weeks earlier had shown only one baby.
Mr Chiew, an army regular, said: 'How rare it is to have triplets conceived naturally. It is a blessing, and a gift from God.'
Ms Lim, a higher technical officer with the Housing Board, said: 'We were not so much concerned about their rarity as we were about their health. We were worried they would be premature and develop complications.'
Even Dr Cheng had been worried, because the three babies were contained within the same protective sac, instead of in separate ones.
Sharing a sac meant they shared the same placenta which supplied oxygen and other nutrients, which increased the risk of one baby taking in more nutrients at the others' expense. An undernourished baby could die in the womb.
To stabilise the pregnancy and keep the babies in the womb for as long as possible, Ms Lim took medication to relax her muscles and prevent premature contractions. She rested at home from mid-October.
She was also given injections to help her babies' lungs mature, so their chances of survival would be improved if they were born early.
But as signs of one baby becoming malnourished began showing on Thursday, Dr Cheng performed a Caesarean section. They had, at the time, been in the womb for 34 weeks, a little short of the full term of 37 to 40 weeks.
At 1.38kg to 1.51kg each, they weigh just half as much as full-term babies.
But Zachariah, Jeremiah and Nehemiah, born one minute apart, are healthy. They do not need breathing or feeding tubes.
Barring infection, they should be discharged from Thomson Medical Centre within a month, said their paediatrician, Dr Keoy Soo Shin.
Their parents and Dr Cheng are relieved they are well. Ms Lim said: 'I hope everything goes well from now - no hiccups, no complications.'
Dr Cheng, 48, has had patients give birth to triplets at least once a year since he began handling fertility treatments at Thomson Medical Centre in 1994. But this is the first set of naturally conceived identical triplets he has delivered.
Last year, one of his patients who had undergone fertility treatment gave birth to triplets, but from two eggs. One of the eggs had divided to produce a pair of identical twins, in addition to the first baby.
Doctors at KK Women's and Children's Hospital do not recall delivering any naturally conceived triplets there.
Since 1986, Singapore General Hospital has delivered 51 sets of triplets, of which three sets were naturally conceived. It is not known if they were identical.
one is enough for us! 
I didn't end up with any multiples and have one daughter and three sons. We were SO glad our youngest wasn't twins since he was such a handful. 
but I don't see why identical twins wouldn't be genetic. Wouldn't/couldn't there be a tendency for fertilized eggs to split completely into two distinct embryos?
However there are factors that help explain identicals, some have suggested that the older you get the weaker the eggs you carry are, thus the easier for them to split into twins. 
