Placental diffusion estimated by MRI in relation to birth weight difference in dichorionic twin pregnancy

Hansen, Ditte Nymark

5. Term (Master thesis)

Medicine, Master

2015

2015-12-21

52

Formål: Store forskelle i fødselsvægt mellem tvillinger kan påvirke deres helbred, men rutinemæssige foster-mål (kronerumpe-længde, abdominalomfang og skønnet fostervægt) forudsiger disse forskelle dårligt. Derfor undersøger man, om markører fra moderkagen kan hjælpe. I enkeltgraviditeter med væksthæmning er moderkagens diffusion blevet rapporteret som nedsat, hvilket gør den til en mulig markør hos tvillinger. I dette studie undersøgte vi, om forskelle i moderkagens tilsyneladende diffusionskoefficient (ADC), målt med diffusionsvægtet MR (DWI), hænger sammen med forskelle i tvillingers fødselsvægt. Metode: Vi gennemgik retrospektivt 1,5T MR-skanninger af moderkagerne med DWI (10 b-værdier fra 0-1000 sec/mm2) fra 17 dichorioniske tvillingegraviditeter (hver tvilling havde sin egen moderkage; gestationsalder 20+4 til 35+4 uger). Én graviditet blev udelukket pga. veer under DWI, så 16 graviditeter indgik. I hver moderkage markerede vi områder i fem snit og beregnede ADC ud fra de tre højeste b-værdier (200-1000 sec/mm2). Forskellen i moderkage-ADC mellem tvillinger blev defineret som ADC for den mindste tvillings moderkage minus ADC for den største tvillings moderkage, i procent af den største. Forskellen i fødselsvægt blev beregnet på samme måde. Resultater: Den gennemsnitlige forskel i moderkage-ADC mellem tvillinger var -0,03 % med stor spredning (SD 9,45 %). Der var ingen signifikant forskel mellem tvillingerne (p=0,989), og der var ingen sammenhæng mellem forskelle i moderkage-ADC og forskelle i fødselsvægt. Konklusion: I denne gruppe af dichorioniske tvillinger var moderkagens ADC målt med DWI-MR ikke en brugbar markør til at forudsige forskelle i fødselsvægt.

Purpose: Large differences in birth weight between twins can affect health, but routine fetal measurements (crown-rump length, abdominal circumference and estimated fetal weight) predict these differences poorly. Researchers therefore explore placental markers. In singleton pregnancies with fetal growth restriction, placental diffusion has been reported to be reduced, suggesting a possible marker in twins. We examined whether differences in the placental apparent diffusion coefficient (ADC)—a measure of how water molecules move in tissue measured with diffusion-weighted MRI (DWI)—are associated with differences in birth weight between co-twins. Methods: We retrospectively reviewed 1.5T placental MRI with DWI (10 b-values from 0-1000 sec/mm2) from 17 dichorionic twin pregnancies (each twin had its own placenta; gestational age 20+4 to 35+4 weeks). One pregnancy was excluded due to contractions during DWI, leaving 16 for analysis. For each placenta, regions of interest were drawn in five slices and ADC was calculated using the three highest b-values (200-1000 sec/mm2). The inter-twin placental ADC difference was defined as the smaller twin’s placental ADC minus the larger twin’s, expressed as a percentage of the larger value. Birth-weight difference was defined similarly. Results: The mean inter-twin placental ADC difference was -0.03% with wide variability (SD 9.45%). There was no significant difference between co-twins (p=0.989) and no association between placental ADC differences and birth-weight differences. Conclusion: In this cohort of dichorionic twins, placental ADC from DWI MRI did not predict birth-weight discordance and was not a useful marker.

[This abstract was generated with the help of AI]

tvillinger ; placenta ; diffusion ; fødselsvægt ; prædiktion

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