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MRCOG PART 2 SBAs and EMQs

MRCOG Part 2, MRCOG 2

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ESSAY 148 - PND

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		Posted by Sarwat F. Fri Feb 18, 2005 05:48 am
Various options available to a woman for determining whether her baby has Downs syndrome include screening and diagnostic tests. She will be counseled that Overall the best test to offer her for screening for downs syndrome is integrated test. It includes determining nuchal translucency of the fetus and serum PAPP A measurement at 10 weeks and checking serum alpha fetoprotein, estriol, human chorionic gonadotrophin and inhibin A at 14 to 20 weeks and integrating the results. She should be told that this test has 85 % detection rate and 1.2% false positive rate. If the facilities of nuchal translucency are not available than she can be offered serum integrated test which includes serum PAPP A measurement at 10 weeks and checking serum alpha fetoprotein, estriol, human chorionic gonadotrophin and inhibin A at 14 to 20 weeks and integrating the results. It has 85 % detection rate and 2.7% false positive rate However if she insists for screening in the first trimester she will be offered combined test which includes measuring nuchal translucency, free beta HCG and serum PAPP A at 10 weeks gestation. This test also has 85 % detection rate with 6.1 % false positive rate so the test with lowest false positive test is integrated test and this is offered, however woman, s choice will take priority. In case she is found screen positive for Downs syndrome, she can be offered diagnostic procedures. These include chorionic villous sampling and amniocentesis. Chorionic villous sampling can be done after 10 weeks. It can be done either thru transabdominal or transvaginal routes. Results can be obtained in 24 to 48 hrs with direct preparation and between 5 to 14 days for culture reports. Accuracy of results is 99.3 %. Its complications include miscarriage (more than with second trimester amniocentesis), infection, placental mosaicism (or confusion of results due to two different cell lines), contamination with maternal tissues. Limb reduction defects are also a complication but do not generally occur after 10 weeks. Amniocentesis can be done after 14 weeks gestation, ideally after 15 weeks. It will also provide results in 48 hrs. It is performed by trans-abdominal route under direct ultrasound guidance. Its complications include miscarriage 0.9%, infection and rhesus sensitization. It is as accurate as CVS. Woman will be counseled that in case her diagnostic test show that the baby is affected with downs syndrome, there is an option for termination of pregnancy which will have much less complications at earlier gestational age. Termination of pregnancy will involve use of prostaglandin and oxytocin and may need evacuation of retained products of conception under general anaesthesia. She will also need hospitalization for 3 to 4 days. To establish the accurate diagnosis, consent for post mortem and karyotyping will also be taken. This will also help in predicting the recurrence risk. In case she wishes to continue pregnancy, she will be counseled regarding the other structural anomalies that occur in downs syndrome including cardiac defects, duodenal atresia, urinary tract abnormalities. She will be told that she will need detailed scanning at 22 weeks for structural anomalies. As the fetus will be high risk, she needs delivery in a tertiary care hospital with neonatal facilities. Intrapartum intervention may be needed for fetal reasons and special care baby unit will also be involved. Patient will also be counseled regarding longterm problems in babies with down syndrome so they can make an informed decision regarding continuing pregnancy or not. Long term complications include learning disabilities, leukaemia, thyroid disease, Alzheimer’s and epilepsy. Written information in the form of leaflets and support with a help line will also be provided.
		Posted by Nibedita R. Fri Feb 18, 2005 12:53 pm
I would enquire about the reason for such request and also ask about any previous pregnancy with Down?s baby and family history of Downs syndrome. At the age of 39years her age specific risk of Downs (without family or personal history) is about 1 in 150 at term. She should know that Downs syndrome implies severe learning disabilities with long term survival (50-55yrs). About 50% of neonates with Downs have structural anomalies involving heart (a-v canal defect), gastrointestinal (duodenal atresia), urinary tract, limb defects and congenital cataracts. In the long run these babies have the propensity to develop leukaemia, thyroid disorders, alzheimers, and epilepsy. I would explore the attitude of the parents towards an affected foetus. A range of screening tests are available which would identify whether a particular baby is at risk for Downs, but the results of screening tests would not give a definitive answer. Definitive diagnostic tests are available which are invasive, expensive and carry risks of complications. Most effective screening test is Integrated Test ? 1.2% false positive result and 85% detection rate. Integrated test includes nuchal translucency (NT), PAPP-A at 10 completed weeks gestation and AFP, Free beta HCG, UE3 and Inhibin-A at 14-28 weeks gestation. Second most effective is Serum Integrated test. This is performed when first trimester ultrasound screening test is not available. Detects 85% downs with 2.7% false positive rate. Integrated test and Serum Integrated test both are combined first and second trimester screening tests. Complete first trimester screening test is Combined test, which includes NT, Free beta HCG and PAPP-A at 10 weeks gestation. Its advantage is single point test with 85% detection rate, however with a high false positive rate (6.1%). Other tests like quadruple test, triple test and double test are associated with high false positive rates. Only NT measurement at 12-13 weeks gestation can give impression of Downs with a high false positive rate (20%). Foetal anomaly scan at 18-20 weeks gestation can detect structural anomalies and soft markers of Downs syndrome. These are abdominal wall defects, cardiac anomalies, duodenal anomalies, choroids plexus cyst, echogenic bowel, early onset IUGR and short femur length. If the foetus is found to be screened positive for Downs, a more definitive test like CVS or amniocentesis is offered. CVS can be performed after 10 weeks gestation by transabdominal or transcervial route with early report within 48 hours. Risk of miscarriage is about 1-2 % (above background). Other risks are, infection, Rh sensitisation and confined placental mosaicism (1%). Limb reduction deformity is unlikely if preformed after 10 week gestation. Amniocentesis after 15 weeks gestation results obtained after 2-3 weeks by cell culture but PCR and FISH give rapid result within 48 hours. Complications include miscarriage 1% (above background), infection, Rh sensitisation and culture failure (0.5%). Advantage of first trimester screening methods is that it gives opportunity to detect at an early gestation. If a women wishes, a more definitive test (CVS) can be performed at this gestation and termination of pregnancy would be offered at an early gestation; which is supposed to be less traumatic for the women (both psychologically and procedure related). I would like to discuss the options available if found to have a baby with Downs ? continuation of pregnancy or termination and the methods of termination with potential complications. If the woman wishes to continue with the pregnancy, I would like to give the information regarding Downs syndrome parenting and support group as well as provide relevant information leaflets
		Posted by Vaijayanti R. Fri Feb 18, 2005 06:39 pm
The woman and her partner are counselled in a non judgemental manner, providing accurate evidence based information. Written information is also supplemented. History will assess the risk of recurrence if a previous offspring was affected, or the woman or her partner is a carrier for the 14:21 translocation( 15% if mother is a carrier, and 1% if father is a carrier) or the 21:21 translocation ( 100% recurrence). Her additional age relate risk would carry the risk of 1 in 150 to 100. She must remember that screening tests will have to be followed by an invasive test to confirm the diagnosis.Invasive prenatal diagnostic tests will be done at a tertiary fetal medicine centre. The Integrated Test ( NT with PAPP A at 10 weeks ; AFP, uE3,free beta HCG and Inhibin A at 14 to 20 weeks) has been proven to be the most effective ? low false positive, cost and safety profiles ( SURSS study). However it would involve 2 visits to the hospital and the confirmatory test would be subsequently delayed to mid trimester. At 10 weeks, the Combined Test may be carried out( NT + PAPP A + free Beta HCG).This carries an 85% detection rate with a false positive of about 6 %. Additional advantage is that the dating scan can be done , as well as identification of gross anomalies ( anencephaly). This also allows for the CVS to be done as a confirmatory test ( risk of associated pregnancy loss 3% above background risk, fetomaternal hemorrhage,placental mocaisism), with the results bring available within 48 hrs. In the event of facility for NT not being available, she can opt for the Integrated serum Screen, ( PAPPA at 10 weeks, followed by AFP, U E3. free beta HCG, and Inhibin A at 14 to 20 weeks). This carries a false positive rate of 2.7% for a detection rate of 85%. Amniocentesis is done as the conformatory test should she decide on the second trimester screen. The risk of pregnancy loss is about 0.5 to 1% above the background risk, along with associated complications of fetomaternal hemorrhage, and culture failure If she does not wish to undergo invasive tests, a detailed anomaly scan at 20 to 22 weeks of gestation could provide some information - soft markers for chromosomal disorders. However only cardiac defects have been found to have any significant correlation with the occurrence of Downs Syndrome ( 40%) Her attitude to an affected fetus is explored as well as the option of TOP should Downs syndrome be confirmed.Early TOP ( in first trimester ) is associated with considerably fewer complications ( hemorrhage, incomplete, infection, psychological) than if done at a later gestational age. The consequences of Downs syndrome are also explained ? risk of structural anomalies involving the cardia( ASD) gastrointestinal tract ( duodenal atresia, Hirschsprungs disease) limbs, low IQ and a shortened life span( average of 50 to 55 years ) development of leukemia, epilepsy , Alzihiemers disease at later stages. She is given any additional information that she may ask for. Contact with support groups is offered. A follow up appointment is arranged for further counselling or for the screening procedure if she so decides.
		Posted by Sonali G. Sat Feb 19, 2005 07:15 am
Incidence of downs syndrome is 1:700 in general population which increases to around 1:100 in woman of 39 years. Her history regarding previous down?s baby is asked which will increase her chance of having downs baby (recurrence risk is age related risk +0.34%) Options available can be in the form of screening tests and confirmatory tests. Screening tests will only help estimation the probability of down?s syndrome which, if positive, (cut off level 1:250). She will be offered invasive confirmatory test. The fact that her age related risk is already high, screening tests won?t be of much value. First of all, her attitude towards an affected baby is explored if she would like to continue her pregnancy or will consider termination. Amongst screening test available, integrated test is the best method (involving 1st trimester muchal translucency (NT) + PAPP A & 2nd trimester bhcg, AFP and S estriol) with detection rate of 85% and false positive rate of 1.2%. If NT is not available, serum integrated test can be offered with false positivity of 2.7%. If she is keen to have screening in 1st Trimester then combined test (NT+AFP+PAPPA) can be offered. 2nd trimester screening tests are in form of quadruple test (with false positivty of 6.2%). And triple test (9.3% false positive rate). The advantage of 1st trimester screening is that it allows earlier termination if needed. 2nd trimester anatomy scan can detect congenital anamolies associated with down?s syndrome like duodenal atresia (double bubble sign), congenital cardiac lesions and other abnormalities. She can be offered invasive tests directly considering her background high risk in the form of chorionic villus sampling(CVS) or aminocentesis.CVS is done between 10-13 weeks either transabominally or transvaginally and the results are available within 24-48 hrs by direct preparation. But the risks associated with it are increased risk of miscarriage (2-3%) above background risk , culture failure and chances of mosaicism(1%) (contamination by maternal cells) Amniocentesis is carried out between 14-18 weeks transabdominally and the results are ready in 2-3 weeks. With the help of FISH, results can be ready in 24-48 hours, but it is also associated with miscarriage risk (1%) which is slightly lower than CVS chances of PPROM and amnionitis. If the diagnosis of Down?s is confirmed, termination will be offered (along with information about its methods and complications) But if she wants to continue with the pregnancy, full support will be provided throughout the pregnancy. The pregnancy will be monitored. Counselling with paediatrician will be offered to explain about the management of neonatal complications. Information regarding support groups will be provided. She should be fully aware of the physical structural disabilities and mental handicap associated with downs before coming to any decision. Information leaflets will be provided and her views documented.
		Posted by Iman B. Wed Feb 23, 2005 10:17 am
At the age of 39 there is an age related risk of developing Downs syndrome. The patient will have a four times increased risk of of having a Down baby after the age of 35 years. A past history may show a previous Down baby, or sibling, or close family member, either with the mother or her partner. If this is the case and in view of her age, she and her prtner should be referred to a geneticist for karyotyping. If she or her partener turn out to be carriers for the translocation (t 21:21) then there is a 100% chance that this baby will have Downs. If she is a carrier for the transloation t 14:21 then there is a 15% chance of her having a Down baby in this pregnancy if the partner is the carrier for t14:21 then the chance is 1% along with the added risk of her age. She should be offered a combined test, where serum bHCG and PAPP-A are measured in serum along with an ultrasound scan where the age of the fetus is identified and presence of nuchal translucency. Nuchal translucency alone is not very sensitive carrying a 20% false positive rate, this compared to the combined test which carries a 6.1% false positive rate. It will largely depend on the mother and the degree of anxiety she is in, and whether she accepts a 6.1 % false positive rate to continue with interventional diagnosis or not. The most sensitive screening test is the integrated, but it will mean that she must wait well into the second trimester before knowing whther ir not the baby has Down. If the mother intends to terminate the pregnancy if the baby were Down, then it is better in the first trimester, where it carries less morbidity than if it were done in the second. The patient should be kept fully informed on the steps of screening and diagnosis she should be gien help lines and numers of support groups, and she should be given leaflets and patient handouts on interventional diagnostic procedures. A positive screening test, should be verified by either chorion villus sampling(CVS) or amniocentesis. CVS carried the advantage that it will not delay the decision of termination, but it has a slightly higher risk of pregnancy loss compared to amniocentesis(1-2%) she will need to go to a specialised center for the CVS as it needs expert team, there is a chance of false results from placental mosaicism, and a chance of failure of the procedure from where amniocentesis will be needed, but on the other hand the result will be available within days. Amniocentesis may be more readly available in centers near by the patients home, it may be done as early as 15-16 weeks, it is safer than CVS, with a pregnancyloss in the range of 0.5-1% . The results are delayed a little maybe upto a one or two weeks, though new techniques as fluorescent hybridaisation(FISH) may be available in the center the patient is going to, in which case the result may come out faster. Before any intervention a 250 IU anti D immunoglobulin should begiven if the patient is RH negative. If the baby were Downs, then she should be given contact numbers of support groups and families with Downs babies, she should be offered psychological support, and gien the decision to keep the baby or terminate the pregnancy. Therapeutic termination should always be followed by anti D if the patient is Rh negative. If she wishes to continue the pregnancy then she must realise that there is a possibility of ongential anomalies as duodenal atresia, cardiac anomalies and that close surveillance will be necessary for the possibility of IUGR and hydrops fetalis.
		Posted by narmin B. Thu Feb 24, 2005 03:44 am
In counselling she should be advised that the risk of Down?s syndrome at her age is about1%, the risk increases if she had a family history or previous baby with Down?s s syndrome. In order to determine that this baby has Down?s syndrome, there are two ways. One way is to do screening tests first which will identify that she is in high risk group or not. Then a diagnostic test is required to confirm the diagnosis. Although this method is less invasive but takes longer to reach a diagnosis The second way is to do a diagnostic test without screening which although is an invasive method but give the opportunity for early diagnosis and management. Different types of screening tests and their availability and diagnostic tests should be discussed. The most sensitive screening test is the integrated test which includes an ultrasound scan for measuring the skin fold behind the fetal neck (nuchal translucency scan NTS) at about 12-13 weeks and serum biochemical tests in the first and second trimester. In the first trimester pregnancy associated plasma protein A and BHCG and in the second trimester HCG, alpha feto protein, inhibin A and oestriol will be measured. This test has a sensitivity of 85% with a false positive rate of 1.2% . This test is not available an all units and also she will need to wait until second trimester to complete the test. The second most sensitive screening test is integrated serum screening. This test involves only biochemical measurement similar to the integrated tests without NTS. This test is advisable when NTS is not available. Sensitivity is around 80% with a false positive rate of about 2-3%. Another screening test is a combined test which includes NTS and first trimester biochemical tests. This has a sensitivity of about 80% with 5% false positive rate. The benefit of this test is early detection of risk, early diagnosis and termination of the affected fetus. Depending on the availability, in the second trimester screening tests are in the form of double test (alpha feto protein and BHCG), triple test (alpha feto protein, BHCG and oestriol) and quadruple test (Alpha feto protein, BHCG, oestriol and inhibin A). The sensitivity is around 75% with 5 % false positive rate. This test is available in most of the units. Second trimester ultrasound scan may reveal soft markers for Down?s syndrome such as acrogenic bowel, short femur, echogenic cardiac foci. Also gross structural abnormalities which can be associated with Down?s syndrome such as atrio-ventricular septal defects, duodenal atresia and abdominal wall defects cab be seen in this scan. The sensitivity of this test is only about 30-40%. After screening if she was in the high risk group for Down?s syndrome, a diagnostic test in the form of chorionic villous sampling(CVS) or amniocentesis is required to confirm diagnosis. CVS involves obtaining chorionic villous sample under ultrasound guidance. It can be performed after 10 week gestation as before this stage it can cause limb reduction. Transabdominal or transvaginal route can be used. Local anaesthetic can be given . The initial result is available in 48 hours by using FISH technique, although it takes up to 2-3 weeks if FISH is not available. The benefit of this method is early diagnosis and termination of affected fetus. The disadvantages are 2% risk of fetal loss and also the affected fetuses may be miscarried before 12 weeks spontaneously. Another diagnostic method is amniocentesis. This method is obtaining amniotic fluid under ultrasound scan for karyotyping. Although it is possible before 15 weeks, but it is associated with 2% risk of fetal loss and limb deformity. After 15 weeks the risk of fetal loss is 1% and there is no risk of deformity. In the counselling session all the questions should be answers clearly and she should be provided with leaflets as it can be difficult to remember all this information. further counselling may be required. If she wishes, an appointment should be arranged for a screening or a diagnostic test.