CHALLENGES IN DETERMINING CHORIONICITY AND DIAGNOSING SELECTIVE FETAL GROWTH RESTRICTION IN MULTIFETAL PREGNANCIES WITH SUSPECTED TWIN-TWIN TRANSFUSION SYNDROME: A CASE REPORT

Problem statement: Chorionicity is a major determinant of perinatal outcome in twin pregnancies. Mortality and morbidity are higher in monochorionic than dichorionic twin pregnancies. A complication associated with monochorionicity is twin-twin transfusion syndrome (TTTS) and selective Fetal Growth Restriction (sFGR). sFGR occurs when the nutrient and oxygen content through the placenta is insufficient for fetal growth in twin pregnancies. The incidences of sFGR in monochorionic and dichorionic pregnancies are 19.7% and 10.5% respectively. TTTS occurs due to abnormal and intercorrelated blood vessels causing an imbalance in blood flow leading to the formation of "recipients" and "donors". Diagnosis depends on the evaluation of the number of placentas, the characteristics of the intertwined membranes, and the fetal sex.

Methods: Case Report.

Results: A 38-year-old woman came for routine antenatal consultation at 34-35 weeks’ gestation. The patient denied any complaints during pregnancy. Detailed fetal ultrasound revealed a monochorionic diamniotic twin pregnancy suggestive towards TTTS with positive T sign and significantly different volumes of amniotic fluid surrounding each fetus. After delivery, a dichorionic diamniotic placenta was present with the first neonate weighing 2610 grams, and normal placenta sized ± 20x20x2 cm, and the second neonate weighing only 510 grams with a placenta sized ± 10x10x1.5 cm. The diagnosis of sFGR during pregnancy was established according to the Delphi criteria that the smaller twin had an estimated fetal weight 25%.

Conclusion: The ideal time to determine chorionicity is in the first trimester of pregnancy compared to the second and third trimester with diagnostic accuracy approaching 100%. Definitive diagnosis in this case was difficult due to the first ultrasound being performed in the third trimester. Confirmation of chorionicity in multifetal pregnancies is challenging for the clinician if performed in the third trimester. The recommended frequency of ultrasound examination in twin pregnancies is once every 2-4 weeks so that detailed monitoring of twin fetal anatomy and physiology can be evaluated stepwise.

Keywords: Chorionicity, Multiple pregnancy, sFGR, Twin-Twin Transfusion Syndrome (TTTS)