How are quadruplets formed?
In the last three years, 2 sets of naturally conceived quadruplets have been born in South Africa. We asked Dr Malika Patel of the Department of Obstetrics & Gynaecology at the University of Cape Town to explain how these rarely occurring multiples are conceived.
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It's been three years since South Africa saw the birth of its last set of quadruplets, and this past July, Capetonian mom Inga Mafenuka joined KZN-based Nobuhle Qwabe in the mom-of-quadruplets club. 

Conceived naturally, the quadruplets were born via C-section and consist of two girls, Bunono and Bungcwele, and two boys, Bubele and Buchule.

Mom and babies are doing well. 


What is it like parenting multiples? Tell us by emailing to chatback@parent24.com and we could publish your letter

A rare occurrence

Not much research has been done on how many multiple births have occurred in South Africa but globally, multiple births make up only 3% of all births

Quadruplets are by far rarer than twins and triplets: 

“Though twins and higher order pregnancies are more common with assisted reproduction, spontaneous quadruplet conception is extremely rare – it is quoted to be between 1 n 512 000 to 1 in 677 000,“  explains Dr Malika Patel of the Department of Obstetrics & Gynaecology at the University of Cape Town

She notes that complications during these pregnancies are more common than not, “…there are 4 babies in the womb, space is limited therefore they are at risk of complications that occur more frequently than with singleton or twin pregnancies.” 

“Maternal complications include… hypertension, gestational diabetes, and anaemia amongst others. There is an increased risk of miscarriage, preterm delivery, intrauterine growth restriction and delivery via caesarean section. In addition, the babies will require close monitoring for neonatal complications associated with early delivery of small babies.” 

Genetically speaking

You may have a general idea of how conception takes place in a multiple pregnancy, with the example of twins the most commonly known.  

In the case of twins, babies can be either:

  • identical twins: where a single egg cell is fertilised by one sperm cell and splits to form two embryos; or
  • fraternal: two separate egg cells are fertilised by two separate sperm cells and results in two embryos.

Identical twins are always the same gender and share the exact same DNA, whereas fraternal twins could be either gender and each will have their own unique genetic make-up. 

With quadruplets, the process becomes a little more complicated, and the possibilities of having all boys, all girls, or a combination of both, as in the case of Inga Mafenuka's quadruplets, depends on a few factors. 

“They can be either fraternal, resulting from fertilisation of 4 eggs with 4 sperm, or identical, resulting from a fertilized egg that splits into 2 or more embryos, or a combination of these,” she says. 

“In the case of fraternal quadruplets the babies can be of any sex, and they will not be identical. It would be like any other brother and sister. However, when they are all of the same sex or there is 2 boys and 2 girls there is a chance that this could have been 2 sets of twins where the 2 girls are a set and the 2 boys are a set that is you have 2 fertilised eggs that have each split into 2 embryos. Remember you can only have babies of the same sex when you have monozygotic twinning (twins developing from the same fertilised egg) because they have identical chromosomal make-up.” 

The possibilities in spontaneous quadruplets are determined by whether: 

  • a single egg cell is fertilised by one sperm cell and splits into four identical embryos – this will result in four identical babies, same gender, same DNA. 
  • four separate egg cells are fertilised by four separate sperm cells and develop into four embryos – here the babies could be either gender and will not have the same exact DNA, but the four siblings are born at the same time.  
  • a single egg cell is fertilised by one sperm cell and splits into 3 identical embryos, while the fourth is a single egg cell fertilised by one sperm cell – this results in triplets of the same gender plus one sibling. 
  • a single egg cell is fertilised by one sperm cell and splits into two identical embryos twice over resulting in two sets of identical twins. 
  • two separate egg cells are fertilised by two separate sperm cells resulting in two separate embryos, along with a single egg cell fertilised by one sperm cell and splits into two identical embryos – here the combination is one set of fraternal twins and one set of identical twins. 

We can't be 100% certain which combination the Mafenuka quadruplets could be though we know it won't be numbers one or three, but we wish Inga all the best on her new journey. 

What is it like parenting multiples? Tell us by emailing to chatback@parent24.com and we could publish your letter. 

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