Vanishing Twin Syndrome: Kelly delivered two placentas but only one baby.

WARNING: This post deals with themes of miscarriage and pregnancy loss. For support, call Sands Australia on 1300 072 637.

When Kelly gave birth to her first child, Jayde, in 1996, she delivered not one, but two placentas.

“The doctors told me that the pregnancy probably started as twins. They said it would have absorbed or vanished at some point early on in the pregnancy so that all that remained was its placenta,” Kelly told Mamamia.

This occurrence is known as Vanishing Twin Syndrome.

“A pregnancy starts off as a twin pregnancy, but one twin miscarries and can no longer be seen on subsequent ultrasounds. The tissue from the ‘vanishing’ twin usually disintegrates and is absorbed into the surrounding tissue of the ongoing pregnancy,” obstetrician Dr Patrick Moloney told Mamamia. 

The syndrome is actually relatively common, reported in 15-30 per cent of twin pregnancies, according to Dr Moloney.

“Ultrasounds can identify twin pregnancies quite early in pregnancy when miscarriage is still common. Early ultrasounds will show the twin sacs then subsequent scans, such as the Down syndrome screening, will show one has miscarried and ‘vanished’,” he explains.

“Sometimes the miscarried twin will completely disintegrate and be ‘absorbed’ into the surrounding tissues. The surrounding tissues include the membranes, the placenta and the other twin.”

This was what doctors believe occurred in Kelly’s case – Jayde’s foetus absorbed that of her vanishing twin.

Not all cases of Vanishing Twin Syndrome will see the twin absorbed which means there can be physical remnants left behind.

“Sometimes the miscarried twin is not absorbed and can be seen on subsequent ultrasounds. It looks progressively smaller when compared to the growing size of the surviving twin. Sometimes the miscarried twin turns into fetus papyraceus where it is flattened and 'mummified'. This may be seen attached to the membranes when the surviving twin is born at full term," explains Dr Moloney.

The reason behind a twin ‘vanishing’ can vary and “many are unexplained, but a common cause is a genetic abnormality dating back to conception."

With the rate of twin pregnancies rising due to advancing maternal age and IVF, rates of Vanishing Twin Syndrome are also rising.

For Kelly though, the use of ultrasound technology wasn’t used as widely when she was pregnant with Jayde.

"They didn’t conduct an ultrasound until 18 weeks back then – at this ultrasound and the ones leading up to my birth, they didn’t really say anything unusual. So, I didn’t know that I had been, at least early on, carrying twins," Kelly said.

"In hindsight, considering I was a single mum at 19, it was a big relief," Kelly said. "I do sometimes wonder though if it would have been identical – there was only one sac so it made me think she would have been identical. Two versions of Jayde would have been interesting!”

Although a relief for Kelly, for some women the experience of losing a twin can be quite traumatic.

"Some women will experience a grief reaction for the lost twin identical to singleton pregnancy miscarriage. This is complicated by the fact that the pregnancy of the surviving twin is still ongoing," Dr Moloney said.

For Kelly’s daughter, Jayde, now 22, finding out she had absorbed her twin came as a bit of a shock.

“I didn’t even know absorbing a twin was a thing, so it was quite a weird concept to think about. When mum told me, I was kind of like 'Woah imagine what it would have been like to actually have a twin'. I also thought oh god... my poor parents. Imagine having two of me! I think one of me was enough for them, especially as a moody teenager. It was also kind of fun to imagine what it would be like to have a twin now and if we would be similar or not.”

But like her mother, Jayde feels completely at peace with it and as if everything happened as it should have.

"In hindsight, I did enjoy growing up as an only child and only grandchild for a period of time. By the time I found out in my mid-teens, I had a sister and two brothers, so I was never upset by it, maybe a bit relieved in a way that I didn’t have another sibling when I was younger. It was more just a really an interesting thing to learn considering I used to want a twin at one point. A bit ironic or full circle in a way."

Dr Patrick Moloney is a specialist obstetrician and founder of GrowMyBaby, an online pregnancy education program. For more, can follow him on Instagram. 

Shona Hendley, Mother of cats, goats and humans is a freelance writer from Victoria. An ex secondary school teacher, Shona has a strong interest in education. She is an animal lover and advocate, with a morbid fascination for true crime and horror movies. You can follow her on Instagram.