The LEMON study is a study that is complementary to the Twinlife study and takes place at the LUMC from 2021-2022. This study focuses on the long-term outcomes of monochorionic twins with a growth difference before birth.

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Monochorionic twins share a single placenta during pregnancy. In 10-15% this shared placenta is unequally shared. This means that one twin has a much smaller part of the placenta to get nutrients from as compared to the other twin. This results in a growth difference during pregnancy. At birth, this leads to a significant difference in birth weight as well. Sometimes one twin can even be almost twice the size of the other twin.

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There are still many questions about the long-term health of these twins with a growth difference. Are the differences that we see at birth also present at a later age? And does the difference in growth also affect the development of the brain, heart or lungs? To answer these questions, our research group at the LUMC started the LEMON study in January 2021. This study focuses on the long-term outcomes of monochorionic twins with a growth difference during pregnancy. For this study, we are currently inviting all twins with such a growth difference born in the LUMC between 2002-2017 for follow-up. This follow-up consists of various measurements in order to get a full picture of the health status of these twins. To assess the neuropsychological development, we perform a development test and a neurological examination (examination of movement). In addition, we perform ultrasound examinations of the heart and large blood vessels and a lung function test to look at the structure and function of the heart and lungs. Furthermore, we measure growth and use the growth curves of the primary care system to study growth patterns in the first years of life. Finally, we take a cheek swab to see if there are any differences in epigenetic signature, which we may be able to relate to the different circumstances that the twins experienced in the womb. These measurements are spread out over two appointments in the LUMC.

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We would not be able to conduct this study without the efforts of the twins and their parents. The enthusiasm for participation is noticeable among both parents and twins. Parents share their experiences, the differences they observe between the twins and sometimes their concerns with us. This is extremely valuable, because after all, they know their children the best. The twins receive more information about what makes them so special, usually with a photo of their own placenta from the archive. In addition, they get to experience two afternoons filled with all kinds of fun tests, from challenging assignments in developmental testing to the chance to see their own heart during the ultrasound examination. Afterwards, they often fanatically compare their answers and results.  

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We would like to say a big thank you to the twins and parents who are participating (and will participate in the future) in the LEMON study. With your help, we have the opportunity to gain more insight into the long-term health of monochorionic twins with a growth difference during pregnancy, so we can improve care for these special twins.