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Radiology
Multifetal Pregnancy Reduction
Built from Obstetric Imaging
What’s inside
8 sections · 92 slides
Overview
- What this topic covers
Why fetal number matters
What carrying three or four fetuses does to mother and baby
- Definition of multifetal pregnancy reduction
- Reduction compared with selective termination
- Prematurity as the main hazard of multiple pregnancy
- 2.2%
- Reading the preterm delivery figures
- Maternal risk in triplets compared with twins
- Rising incidence of multifetal pregnancy
- Primary and secondary prevention of higher-order pregnancy
- Origins and stated benefits of the procedure
- Two gestational sacs on early ultrasound
- From extra fetuses to perinatal harm
Assessment and counselling before reduction
Ultrasound, chorionicity and an honest conversation
- Setting and timing of the procedure
- Nondirective counselling
- Ultrasound findings needed before counselling
- Chorionicity
- Dividing membrane of a dichorionic twin placenta
- Complications specific to monochorionic twins
- Contraindication to potassium chloride in monochorionic twins
- Cord occlusion techniques for monochorionic fetuses
- Chorionicity decides the reduction technique
- Monochorionic twins inside a higher-order pregnancy
- Risks of the procedure
Genetic screening and testing
What is known about each fetus before one is chosen
- Why genetic testing is offered before reduction
- Prenatal tests and the weeks at which each is used
- Nuchal translucency screening in twins
- Adding serum screening and the nasal bone
- Cell-free DNA testing in twin pregnancy
- What SNP-based cell-free DNA adds
- Screening limits in triplets and higher-order pregnancy
- Chorionic villus sampling before reduction
- Chorionic villi and decidua compared
- Accuracy and safety of sampling in multiples
- Chorionic villus sampling and pregnancy loss
- Recommendation on testing before reduction
Technique
Timing, route, choosing the target and the injection itself
- Timing between 11 and 13 weeks
- Transabdominal versus transvaginal route
- Transabdominal approach under real-time ultrasound guidance
- Reading the transabdominal approach diagram
- Ultrasound-guided needle through the abdominal wall in pregnancy
- Choosing which fetus to reduce
- Why the presenting fetus is spared
- Mapping the sacs before reduction
- Reading the pre-procedure sac map
- Sterile preparation and needle choice
- Needle advanced to the fetal chest
- Steps of the injection
- Sequence of the reduction procedure
- Confirming the reduction is complete
- Cardiac activity in the retained fetuses and none in the reduced fetus
- Colour Doppler over the reduced fetus
- Care immediately after the procedure
Fetal and neonatal outcomes
What the studies show about loss, prematurity and survival
- Where the outcome evidence comes from
- Operator experience and pregnancy loss before 24 weeks
- What the falling loss rate means
- The 1000-case single-centre series
- 38.0 wk
- Starting number, finishing number and loss
- Starting Fetal Numbers and Pregnancy Loss Rates
- Reading the starting-number table
- Triplet to twin: the Lipitz comparison
- Triplet to twin: the second cohort
- Trichorionic triplets: reduced to twins or managed expectantly
- Statistical significance of those differences
- Meta-analysis of triplet-to-twin reduction
- What the meta-analysis settles
- Triplet to singleton: the trichorionic cohort
- Triplet to singleton: the Zemet cohort
- Where the triplet-to-singleton evidence stands
- Twin to singleton: the earliest comparison
- Two cohorts that disagree on twin-to-singleton reduction
- The Danish national cohort
- Verdict on reducing dichorionic twins to a singleton
- Why monochorionic twins are a separate case
- How monochorionic reduction is carried out
Maternal outcomes
How changing fetal number changes the mother's own risks
- Why maternal risk follows fetal number
- Complication rates by number of fetuses
- Reading the complication rates
- Caesarean delivery after reduction
- Gestational diabetes and preeclampsia after reduction
- Severe preeclampsia and HELLP after reduction to a singleton
Key points
The six statements this topic closes with
- Key points on incidence and purpose
- Key points on technique and counselling
- The topic in one screen
- Suggested readings
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition