Twins Flashcards
Explain to a patient what MCDA twins means
Monochorionic means that your twins share a placenta. Diamniotic means that the twins sit in separate sacs of amniotic fluid
Explain to a patient what DCDA twins means
Dichorionic means the twins have separate placentas. Diamniotic means the twins have separate amniotic sacs.
A patient asks whether their DCDA twins are ‘identical’. What do you tell them?
Monozygotic or identical twins arise from the division of a single embryo. If this happens very early after fertilisation this can result in identical DCDA twins. There can also be DCDA twins that arise from two separate embryos. Unless they are of different sexes i.e. male and female, you won’t know if they are identical or not antenatally unless invasive prenatal testing takes place.
Outline routine antenatal care and surveillance for DCDA twins
- Booking bloods.
- Dating and chorionicity scan by 14 weeks.
- Folic acid, iodine, iron.
- General pregnancy advice: food, vaccinations, lifestyle
- Aneuploidy screening
- Routine visits every 2 weeks after 16/40.
- Anatomy scan 18-20 weeks + TVCL.
- Advice: TPL, PET
- Growth scans +/- UAPI Q4W
- Check for PET, proteinuria and BP every visit.
- Midtrimester bloods: OGTT, FBC, red cell antibody screen.
- Routine visits every week from 34 weeks.
- Delivery 37-38 weeks.
Outline routine antenatal care for MCDA twins
- Booking bloods
- Dating and chorionicity
- Folic acid, iodine, iron
- General pregnancy advice: food, vaccine, lifestyle
- Aneuploidy screening
- Routine visits every 2 weeks from 16/40
- Advice re: PTL, PET, TTTS
- TTTS surveillance USS from 16/40 every 2 weeks: SDP, UAPI, stomach/bladder.
- TERTIARY anatomy scan and fetal ECHO 18-20/40
- Growth USS every 2 weeks.
- Add MCA PSV from 24/40.
- PET surveillance: sx, proteinuria, BP every visit.
- Midtrimester screening: FBC, OGTT, antibody screen
- Weekly visit from 32/40.
- Delivery by 36-37/40
Counsel a woman on combined MSS-1 + NT scan for aneuploidy screening in twins
Good sensitivity 90% however less than if singleton pregnancy. Higher false positive rate 10% for MC twins and 5% for DC twins.
Abnormal NT may reflect other abnormalities e.g. TTTS.
Counsel a woman on NIPT testing in twin pregnancies
Blood test assessing fetal DNA in maternal blood stream.
Good sensitivity still 99% for T21, 85% T18; MZ twins perform better than DZ twins.
Higher failed test rate 5% due to lower fetal fraction
Counsel woman about amniocentesis in twin pregnancies
DC: both sacs sampled.
MC: only one sac sampled if chorionicity confirmed <14/40 and there is concordant growth and anatomy.
Can be combined with selective reduction procedure.
Risks: miscarriage 0.6%; loss of amniotic fluid; infection; bleeding.
Counsel woman on risks for all twin pregnancies
Maternal: miscarriage, hyperemesis, GDM, PET, PTL, abruption, VTE, stillbirth, C/S, PPH, maternal death.
Fetal: structural and chromosomal anomalies, IUGR, low BW, PTB, SB, malpresentation,
Counsel woman on specific risks and complications associated with MC twins:
- sIUGR
- TTTS
- TRAP sequence
- TAPS
- Neurological injury or death of co-twins following demise of one twin.
- MCMA: cord entanglement
Selective IUGR MC twins
EFW <10th or discordance >20%.
Caused by unclear sharing of placenta.
Gratacos classification:
Type 1: normal or raised UAPI with forward flow. Benign course, deliver by 34-36 weeks.
Type II: persistent AEDF or REDF. High risk of IUD. Inpatient mgmt, steroids, deliver by 32/40 by CS.
Type III: intermittent AEDF or REDF. High risk of acute feto-fetal transfusion. Inpatient mgmt, steroids, delivery by 32/40 via CS.
Mgmt options: conservative, cord occlusion of FGR twin, laser photocoagulation with likely demise of FGR twin.
TTTS CRITO
Condition: imbalance of fetal blood flow through communicating AV anastomoses; underperfusion donor twin and overperfusion of recipient twin.
Risks:
- Donor: IUGR, oligohydramnios
- Recipient: volume overload/heart failure, polyhydramnios, PTB.
- Multiorgan ischaemia and death in surviving co-twin.
Investigations:
- USS: DVP, bladder/stomach, UAPI, evidence of hydrops.
Treatment:
- Refer to MFM
- Conservative: only for stage 1.
- Laser photocoagulation: early onset <26 weeks. Amnioreduction can be performed at same time. Risks: SROM, PTB, fetal distress, fetal death, placental abruption.
- Selective termination with cord occlusion.
- Steroids
Ongoing management:
- Monitoring: weekly USS for two weeks; then every 2 weeks.
- Risk after photocoagulation or recurrent TTTS, TAPS, perinatal mortality.
- Delivery by 34+0 to 36+6.
TRAPS CRITO
Condition: normal pump twin pumps deoxygenated blood via umbilical artery anastomoses in reverse direction to acardiac twin.
Risks: acardiac twin cannot survive. Pump twin at risk of heart failure, hydrops, PTB and death.
Investigations: USS (fetal ECHO; colour flow doppler; EFW ratio; evidence of hydrops; DVP)
Treatment:
- Conservative
- Cord occlusion of acardiac twin
- Laser photocoagulation
- Delivery once viable gestation.
Ongoing management: USS every week including fetal ECHO if expectant mgmt.
Acute feto-fetal transfusion syndrome CRITO
Condition: IUFD or transient bradycardia in one twin leading to sudden and large unidirectional flow from ‘acute donor’ twin to recipient twin
Risks: acute donor twin at risk of anaemia, brain injury, death.
Investigations:
- USS: MCA PSV for anaemia (>1.5 MoM)
- CTG
- Fetal MRI 4-6 weeks after co-twin death.
Ongoing management:
- Refer to MFM
- Delivery indications: abnormal CTG, severe anaemia.
- Paediatric neurodevelopmental follow-up.
TAPS CRITO
Condition: slow transfusion of blood from donor to recipient twin.
Risks: anaemia/heart failure/hydrops in donor; polycythaemia in recipient: fetal demise of either.
Investigations: MCA PSV
Treatment:
- Referral to MFM
- Expectant
- Laser photocoagulation
- In-utero transfusion
- Selective cord occlusion
- Early delivery.
Ongoing management:
- Postnatal: umbilical cord bloods.
