Multiple pregnancy

Question 1

Multiple pregnancy - incidence (UK)

Answer 1

1. Twins = 15:1000
2. Triplets = 1:5000
3. Quadruplets = 1:360,000

Question 2

Multiple pregnancy - risk factors

Answer 2

1. Previous multiple pregnancy
2. Family history
3. Increasing parity
4. Increasing maternal age
5. Assisted reproduction (clomiphene, intrauterine insemination, IVF with two-embryo transfer)

Question 3

Multiple pregnancy - types

Answer 3

1. Dizygotic twins
   - Result from two separate ova being fertilised by different sperm, simultaneously implanting and developing
   - Consequently, these fetuses will have separate amniotic membranes and placentas (dichorionic and diamniotic - DCDA)
   - Twins may be different sexes
2. Monozygotic twins
   - Result from division into two of a single, already developing embryo
   - Genetically identical and always of the same sex
   - Whether they share the same amniotic membrane and/or chorion depends on the stage of development when the embryo divides
   a. Monochorionic diamniotic (MCDA) - divides at 4-7d
   b. Monochorionic monoamniotic (MCMA) - divides at 8-12d
   c. Conjoined twins (very rare) - divide at >12d

Question 4

Multiple pregnancy - sx/dx

Answer 4

Sx

1. Hyperemesis gravidarum
2. Uterus larger than expected for dates
3. 3 or more fetal poles may be palpable at >24 weeks
4. Two fetal hearts may be heard on auscultation

Dx
5. Vast majority dx on ultrasound in first trimester (dating or nuchal translucency scan). Can determine chorionicity in this scan (?)

Question 5

Multiple pregancy - antenatal mx

Answer 5

1. All multiple pregnancies are ‘high risk’ - should be consultant led
2. Consider iron and folate supplements. Advise aspirin 75mg od if additional risk factors for preeclampsia
3. More frequent antenatal checks required bc increased risk of preeclampsia. Perform detailed anomaly scan. Serial growth scans at 28, 32 and 36 weeks for DC twins. Surveillance needs to be more intensive for MC twins - refer to specialist fetal medicine team.
4. Discuss mode, timing and place of delivery. Establish presentation of leading twin by 34 weeks
5. Offer delivery at 37-38 weeks - induction or LUSCS (lower uterine segment caesarean section)

Question 6

Multiple pregnancy - maternal risks

Answer 6

1. HG
2. Anaemia
3. Pre-eclampsia (5x risk c/w singleton)
4. GDM
5. Polyhydramnios
6. Placenta previa
7. APH
8. PPH
9. Operative delivery
10. Other symptoms of pregnancy - GORD, backache

Question 7

Multiple pregnancy - fetal risks

Answer 7

1. Miscarriage
2. IUGR
3. Preterm labour (40% before 37 weeks, 10% before 32 weeks)
4. Perinatal mortality
5. IUD (stillbirth)
6. Disability
7. CP
8. Vanishing twin syndrome

MC twins only:

9. Congenital abnormalities (including neural tube defects, cardiac abnormalities and gastrointestinal atresia)
10. Twin-to-twin transfusion syndrome

Question 8

Twin-to-twin transfusion syndrome - general

Answer 8

1. Affects 5-25% of MC twin pregnancies. If left untx, 80% mortality rate
2. Caused by aberrant vascular anastomoses within the placenta, which redistribute the fetal blood
3. MC twins require intensive monitoring, usually in the form of serial U/S every 2wks from 16-24 weeks and every 3wks until delivery. Best performed in a specialist fetal medicine unit

Mx

4. Laser ablation of placental anastomoses (associated with lowest risk of neonatal handicap)
5. Selective feticide by cord occlusion = reserved for refractory disease

Question 9

Selective intrauterine growth restriction - general

Answer 9

1. Growth discordance - more common than TTS
2. Variable pattern of umbilical artery Doppler (e.g. intermittent absent/reversed end diastolic flow) indicates a high risk of sudden demise

Mx
3. If >28 weeks, delivery safest. If

Question 10

TTTS - effects on fetus

Answer 10

Donor twin

1. Hypovolaemia and anaemia
2. Growth restriction

Recipient twin (often more at risk than donor)

3. Hypervolaemic and polycythaemic
4. Cardiac overload and failure; large bladder (?)
5. Evidence of fetal hydrops (ascites, pleural and pericardial effusions)

Question 11

Intrauterine death of twin (3)

Answer 11

Dichorionic

1. Death of one twin in 1st trimester or early part of 2nd does not appear to adversely affect the remaining fetus
2. Loss in late part of 2nd or 3rd trimester usually precipitates labour, with 90% having delivered within 3 weeks

Monochorionic
3. Bc shared circulation, subsequent death or neurological damage from hypovolaemia occurs in 25%. Delivery does not decrease the risk of brain injury

Question 12

Multiple pregnancy - labour

Answer 12

1. For vaginal delivery, leading twin should be cephalic (80%), and there should be no absolute contraindications
2. If leading twin breech, CS indicated (risk of second twin being cephalic -> locking heads -> death)
3. Epidural analgesia often recommended bc may need manipulation of second twin (ECV or internal podalic version - locating a foot which is then pulled down into the vagina may be used to deliver the second twin
4. Triplets and higher order multiples usually delivered by CS
5. Delivery should be in a hospital, with an experienced obstetrician, paediatrician and anaesthetist available. IV access and CTG needed

Question 13

Multiple pregnancy - intrapartum risks

Answer 13

1. Malpresentation
2. Fetal hypoxia in second twin after delivery of first
3. Cord prolapse
4. Operative delivery (already covered in maternal risks)
5. PPH (already covered in maternal risks)