TEMPLATE DESIGN © Down syndrome in both Dichorionic Twins: A case Report B. Towobola, S. Bazuaye, J. Obrycki Causeway Hospital,Coleraine, United Kingdom Objectives To report a rare case of dichorionic twins both affected by Down syndrome, diagnosed after birth. To highlight the potential consequences of failure of antenatal diagnosis of the condition. Introduction Case presentationConclusions References This case highlights a rare situation where a 27 year old patient delivered both dichorionic twins with Down syndrome that was not diagnosed prenatally. This will have significant and long-lasting psychological impact on the mother and the entire family as it results in a range of problems for both children; primarily intellectual impairment which could be severe in 80% compared with mild or no intellectual impairment in 20% of cases. They are also at increased risks of mortality and morbidity due to congenital malformations e.g, cardiac defects, increased risk of leukamia, thyroid disorder, epilepsy and Alzheimer’s disease. OPTIONAL LOGO HERE Michele P. Mohajer. Biochemical Screening. Obstetrics & Gynaecology. An evidence-based text for MRCOG. Edited by David M. Luesley, P N. Barker p 208. Reduced fetal movement. (Green top 57). Royal college of Obstetricians & Gynaecologists Labour and Delivery Pregnancy Complications Labour and Delivery Pregnancy Complications Otaigbe B E. Down syndrome in one of non-identical twins. Niger J Med.Otaigbe B ENiger J Med Jan-Mar; 16(1):74-6. Buckley SJ. How often are children with Down syndrome twins?. Down Syndrome News and Update. 2003;3(1);10-10 Nelson Textbook of Paediatrics, 18 th Edition. Down's syndrome in twins of unlike sex, Journal of Medical Genetics, 1983, 20, Prenatal Screening for and Diagnosis of Aneuploidy in Twin Pregnancies JOINT SOGC-CCMG CLINICAL PRACTICE GuIDELINE No. 262 (Replaces No. 187, February 2007) Karyotype in Down syndrome Down syndrome (Trisomy 21) is the commonest chromosomal abnormality. It occurs in 1: 600 – 800 of all births. It is caused by an extra chromosome 21. In dichorionic twins, the risk of aneuploidy is that of each of the individual fetuses and its occurrence in both dichorionic twins is very rare. In the population of 15,000 babies with Down syndrome, all multiple births occur at a rate of about 2%. A total of 244 twin pairs are recorded (some prenatally diagnosed), including 29 pairs (11.8%) where both have Down syndrome. Of all births, identical twins with Down syndrome occur at the rate of 1 or 2 in a million pregnancies and non-identical twins at the rate of 14/15 in a million. This case report was done by reviewing patient’s case notes, journal search and obtaining verbal consent from the patient. This is a case of a 27 year old nulliparous Caucasian lady with dichorionic twins both affected by Down syndrome. She had history of essential hypertension, was on labetalol 200mg twice daily and her blood pressure was well controlled. She had no other medical conditions and no family history of congenital or genetic abnormalities. Her booking was at 13weeks + 4days, when chorionicity was determined as dichorionic by an experienced staff grade obstetrician. Nuchal transluscency scan was not done at this time and no screening tests for genetic abnormalities were arranged. Increased nuchal translucency thickness Structural anomaly scan at 20 weeks gestation was normal for twin 1 while that of twin 2 was said to be inconclusive after two attempts. No further arrangements were made to do a more detailed scan. Both fetuses had shown concordant growth on antenatal scans until she presented with reduced fetal movements at 35 weeks + 3 days. Transabdominal scan for fetal wellbeing then showed decreased end diastolic flow on the umbilical artery doppler of twin 2. She was admitted for fetal surveillance, including twice daily cardiotocogragh and daily umbilical artery doppler. A category 2 caesarean section was performed at 36 weeks + 4 days gestation, indication being reverse end diastolic flow in the umbilical artery doppler of twin 2. The birth weights were 2.1 and 2.2 kg for twin 1 and twin 2 respectively, both with Apgar scores of 9 at 5 minutes. Twin 1 was observed to have reduced oxygen saturations while slightly reduced tone was noted in both of them. Also, further neonatal examinations revealed flat palpebral fissures, low-set ears and sandal gap in both twins. Echocardiogram was concordant for cardiac abnormality and both twins subsequently had Karyotype and Rapid Fluorescence In situ Hybridization (FISH) test that confirmed Trisomy 21 (47XY ). Discussion In this case report, we have described Down syndrome in both dichorionic twins, a rare occurrence. The risk of having a baby with Down syndrome increases with age and is not common in younger mothers like the 27 year old described in this case. The incidence increases with maternal age, from 1 in 1500 under the age of 25, to 1 in 1000 at age 30, 1 in 100 at age 40 1, which is the commonest. Even though younger women have a lower risk, their higher overall birth rate means that they represent half of all mothers with babies with Down syndrome. No family history of congenital or genetic abnormalities was reported in this patient. Down syndrome is caused by Trisomy 21 in 95 percent, Mosaicism in 2 percent and Robertsonian translocation in 3 percent of cases. Mosaicism is a mixture of normal diploid and trisomy 21 cells and Robertsonian translocation occurs when all or part of an extra chromosome 21 is fused with another chromosome. Some cases of Down syndrome are inherited form a parent with translocation balanced by a chromosome deletion. However, most translocations are sporadic. No screening tests were carried out to rule out genetic abnormalities in this patient. Fetal nuchal translucency in combination with maternal age can be used in first trimester as a screening test for aneuploidies in twin pregnancies. First trimester serum screening combined with nuchal translucency may also be considered. It decreases the false positive rate observed with the use of nuchal transluscency and maternal age alone. Structural anomaly scan at 20 weeks gestation and normal for twin 1 but inconclusive in twin 2. Currently, there is no robust evidence to recommend using ultrasound for soft markers for aneuploidy in twins.. Examination of both babies after birth revealed flat palpebral fissures, low-set ears and sandal gap deformity. These distinctive characteristics are typical in Down syndrome Sandal gap deformity Features of Down syndrome