Vanishing Twin Syndrome

Vanishing Twin Syndrome occurs when one twin in a multiple pregnancy disappears during gestation, often in the first trimester. This happens because one of the foetuses stops developing and is absorbed by the mother’s body or the surviving twin. Many women may not even realise they were carrying twins, as the only signs can be mild symptoms such as slight cramping or bleeding. An early ultrasound scan may initially show two gestational sacs, but later only one is visible.

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The exact cause of Vanishing Twin Syndrome isn’t always known, but it often involves chromosomal abnormalities in the undeveloped twin. These abnormalities can lead the affected twin to stop developing and be gradually absorbed. In most cases the remaining twin continues to grow normally and the pregnancy proceeds without further complications.

Vanishing Twin Syndrome occurs in some twin or multiple pregnancies detected in the first trimester. It typically happens within the first 12 weeks of gestation, often before the mother is aware she is carrying multiples. Advances in ultrasound technology have increased diagnosis rates, as early scans can now reveal multiple gestational sacs. The wider use of assisted reproductive technologies such as in vitro fertilisation (IVF) has also increased the number of multiple pregnancies and, consequently, instances of the condition.

Many women experience no noticeable symptoms at all, which is why the condition is often only identified on an ultrasound scan. Where symptoms do occur, they can be mild — for example slight cramping or bleeding. Because these signs are non-specific and common in early pregnancy, they do not on their own confirm a vanishing twin.

If you have concerns about your pregnancy or baby's wellbeing, contact your midwife, GP, or maternity unit promptly.

Vanishing Twin Syndrome is usually identified through ultrasound. An early scan may initially show two gestational sacs, while a later scan shows only one, indicating that one twin has stopped developing and is being absorbed. Advances in ultrasound technology have improved detection, as early scans can now reveal multiple gestational sacs more clearly.

In most cases the surviving twin continues to develop normally and the pregnancy proceeds without significant complications. The remaining twin usually grows as expected once the other twin has been absorbed. Your specialist can monitor the pregnancy with ultrasound and discuss what to expect in your individual circumstances.

Vanishing Twin Syndrome is generally not a condition that is treated, as it reflects a natural process in early pregnancy where one twin stops developing and is absorbed. In most cases the surviving twin continues to grow normally and the pregnancy proceeds without significant complications. Care usually focuses on monitoring the ongoing pregnancy with ultrasound rather than any specific intervention. Please discuss your individual circumstances with our specialists, who can advise on appropriate monitoring for you.

This information is intended for general educational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional for guidance specific to your individual circumstances.

In most cases, once one twin has been absorbed the surviving twin continues to develop normally and the pregnancy proceeds without significant complications. Because individual circumstances vary, any specific concerns about your pregnancy are best discussed with our specialists, who can review your scans and history. This information is intended for general educational purposes only and does not constitute medical advice.

If you have concerns about your pregnancy or baby's wellbeing, contact your midwife, GP, or maternity unit promptly.

Learning about a vanishing twin can be an emotional experience, and it is understandable to have a range of feelings even when the surviving twin is developing normally. Everyone responds differently, and there is no right or wrong way to feel. Our specialists are happy to talk through what the diagnosis means for you, and your midwife or GP can also point you towards further support if you would find it helpful.

This information is intended for general educational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional for guidance specific to your individual circumstances.

Yes. Non-Invasive Prenatal Testing (NIPT) analyses cell-free fetal DNA circulating in the mother’s bloodstream, and in a vanishing twin pregnancy residual DNA from the demised twin may still be present. This residual DNA can interfere with results, potentially leading to false positives or inconclusive findings, as the test may detect chromosomal anomalies from the non-viable twin rather than the healthy one. Recent advances in bioinformatics and DNA sequencing have improved accuracy by better distinguishing between the DNA of the surviving and vanished twins.

At LPC we offer two tests that can work with vanishing twins: PrenatalSafe NIPT and PrenatalSafe Complete Plus NIPT. You need to wait at least 5 weeks after the vanishing twin is diagnosed on ultrasound before having the NIPT.