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Complicated twin pregnancies.

Growth discordance in twin pregnancies is diagnosed when there is a difference of 25% between the two fetuses. The causes of discordant growth in fetuses depend on the placentation. In monochorionic pregnancies the incidence is between 7% and 25%, with a mortality rate between 9% and 11%. The causes of growth discordance in dichorionic twins are the same as for singletons, while the causes of monochorionic twin pregnancies include the following: discordant placental sharing, discordant implantation, placental transfer of nutrients and differences in insulin-like growth factors.

Screening of twin pregnancies includes more than just screening for trisomies, and in monochorionic pregnancies includes methods to predict pregnancies at risk of developing complications. Factors that need to be evaluated are: discordance in NT, amniotic fluid and abdominal circumference. The time to screen is at the first trimester scan and then again at 16 weeks. The timing of delivery of discordant growth monochorionic twin pregnancies is controversial. Some units advocate delivery at 32 weeks but other units follow them up and deliver closer to term.

Selective intra-uterine growth restriction is classified based on Doppler of the umbilical arteries. Type 1 has positive end-diastolic flow, type 2 has absent or reversed end diastolic flow constantly and type 3 has intermittent absent or reversed end-diastolic flow. Type 3 has the highest associated perinatal mortality incidence of 15.4%. In these cases, ductus venousus and pulsatility index of the middle cerebral artery Doppler are used for prediction.

The management of selective IUGR depends on the chorionicity. In cases of monochorionic pregnancies selective cord occlusion can be done in severe cases before 26 weeks. If the patient is further than 26 weeks, admission and intensive fetal monitoring are advised. In cases of selective IUGR in dichorionic pregnancies the healthy fetus will dictate management until the intact survival of that fetus is certain, and then the sick fetus will determine when to deliver.

In cases of discordance for structural anomalies the chorionicity will also determine management. In cases of monochorionic twins selective cord occlusion is done, and in cases of dichorionic twin pregnancies intra-cardiac potassium injection is used.

H Lombaard

Dr Lombaard did his pre-graduate training at the University of Pretoria, graduating in 1997. He did community service at Kgapane Hospital and then trained in the Department of Obstetrics and Gynaecology, University of Pretoria. After obtaining his MMed and FCOG (SA) he stayed on as a consultant in Obstetrics and Gynaecology at Kalafong and trained in fetal medicine under Professor Bridgette Jeffery. He also spent time in Bristol under Professor Peter Soothill as a Fellow in Fetal Medicine. He obtained his registration as a subspecialist in Maternal and Fetal Medicine in 2007, and since October 2009 has been head of the Maternal and Fetal Medicine Unit at Steve Biko Academic Hospital.

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Title Annotation:SASUOG Congress 2010: 7-9 May 2010, Ilanga Estate, Bloemfontein
Author:Lombaard, H.
Publication:South African Journal of Obstetrics and Gynaecology
Geographic Code:6SOUT
Date:Apr 1, 2010
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