Multiple Pregnancy Flashcards
What is the incidence of twins and triplets?
Twins = 1 in 80
Triplets = 1 in 1000
Incidence increasing due to fertility treatments
List the types of multiple pregnancy
- Dizygotic twins
2. Monozygotic twins
What are the key points about dizygotic twins?
- 2/3 of all multiple pregnancies
- Fertilisation of different oocytes by different sperm
- May be of different sex
- No more genetically similar than siblings from different pregnancies
What are the key points about monozygotic twins?
- Mitotic division of single zygote into ‘identical twins’
- Sharing of amnion or placenta depends on time of division:
- Division before day 3 = dichorionic diamniotic
- Between days 4-8 = monochorionic diamniotic
- Later division (9-13) = monochorionic monoamniotic
- Incomplete division = conjoined twins
What is the aetiology behind multiple pregnancy?
- Assisted conception
- Genetic factors
- Increasing maternal age and parity
How can we diagnose multiple pregnancy?
- Vomiting may be more marked in early pregnancy
- Uterus larger than expected for dates and palpable before 12wks
- Most diagnosed at US
List the maternal complications of multiple pregnancy
- All obstetric risk exaggerated
- GDM + pre-eclampsia more frequent
- Anaemia
List the fetal antenatal complications of all multiple pregnancies
- Greater mortality and long term handicap:
- IUGR
- Preterm delivery
- Monochorionicity - Miscarriage:
- One twin early on
- Increased late miscarriage - Preterm labour
- IUGR
- Congenital abnormalities:
- More common per baby in MC twins
List the complications of monochorionicity
- Twin-twin transfusion syndrome (TTTS)
- Twin anaemia polycythemia sequence (TAPS)
- Twin reversed arterial perfusion (TRAP)
- IUGR more common
- Co-twin death
- Monoamniotic twins - cord entanglement and in utero demise due o shunting of blood between two babies
What is twin-twin transfusion syndrome (TTTS)?
- Only in MCDA twins
- Unequal blood distribution through vascular anastomoses of the shared placenta
- Staged according to Quintero in stages 1-5
- High risk of in utero death or severely preterm delivery
What happens to the ‘donor twin’ in TTTS?
- Volume depleted
- Develops anaemia
- IUGR
- Oligohydramnios
What happens to the ‘recipient twin’ in TTTS?
- Volume overloaded
- May develop polycythemia
- Cardiac failure
- Massive polyhydramnios
Describe the Quintero Classification
Stage I:
- Significant discrepancy in amniotic fluid volume
- Bladder of donor twin visible
- Doppler studies normal
Stage II:
- Bladder of donor twin is not visible
- Doppler studies not critically abnormal
Stage III:
- Doppler studies are critically abnormal in either the donor or recipient twin
- Abnormal or reversed end-diastolic velocities of the umbilical artery in the donor
- Abnormal venous Doppler velocities in the recipient
Stage IV:
- Ascites, pericardial or pleural effusion
- Scalp oedema or overt hydrops present unusally in recipient
Stage V:
- One or both babies are dead
How is TTTS managed?
- Fetoscopic laser coagulation is the treatment of choice if diagnosed before 24wks
- Solomon technique (complete ablation along vascular equator rather than selective ablation) is preferred technique
- If complicated by this after 26wks DELIVER
- Survival of both twins = 50%; one twin = 80%
What is twin anaemia polycythemia sequence (TAPS)?
- Marked haemoglobin differences between MC twins in absence of liquor volume changes characteristic of TTTS
- Consequence of small placental anastomoses
- Can follow incomplete laser ablation for TTTS
What is twin reversed arterial perfusion (TRAP)?
- Rare
2. Abnormal, often acardic fetus is perfused by a normal ‘pump’ twin which is at risk of cardiac failure
What is IUGR like in monochorionic twin pregnancies?
- Selective IUGR with intermittent absent or reversed end diastolic flow
- Umbilical artery waveform of smaller twin very erratic
- Growth discordancy
What happens when there is co-twin death in monochorionic twin pregnancies?
- One of twins dies, the drop in its BP allows acute transfusion of blood from the other twin
- Rapidly leads to hypovolaemia and death or neurological damage (30%)
- Survivor of dichorionic twin pregnancy not at risk as circulation not shared
List the intrapartum complications of multiple pregnancies
- Malpresentation of first twin - 20%; C-section
- Fetal distress in labour - second twin delivered has increased risk of death (5x); second twin may present as breech
- PPH (10%)
What is the standard antepartum management of all multiples?
- General:
- Pregnancy considered high risk
- Consultant led care
- Iron and folic acid supplements
- Low-dose aspirin if other risk factors for PET
- Discuss postnatal home help - Early US:
- Chorionicity must be accurately determined in first trimester
- Dichorionic twins = lambda sign
- Monochorionic twins = T sign
- Twins of opposite gender always dizygotic - Identification of risk for preterm delivery:
- TVUS of cervical length not advised
- PV progesterone or cervical cerclage not useful in multiple pregnancy - Identification of IUGR:
- US examinations and consultations every 4wks from 24wks to 36wks and weekly thereafter (uncomplicated DC twin pregnancy) - Timing of delivery:
- Delivery at 38wks for DC twins
- Delivery at 37wks for uncomplicated MC twins
What is the antepartum management specific to MC twins?
Uncomplicated MC twin pregnancy = antenatal visits every 2-3wks from 16wks to delivery
How are higher order multiple pregnancies managed antepartum?
- Surveillence = according to chorionicity
What modes of delivery are used in multiple pregnancy and when are they used ?
- C-section:
- If first fetus is breech or transverse lie
- If higher order multiples
- If there have been antepartum complications - Vaginal delivery:
- When first fetus is cephalic
How is the delivery managed?
- CTG advised
- Epidural analgesia helpful
- Good communication with and comfortable position for mother
- Contractions often diminish after first twin
- Perform ECV if lie of second twin not longitudinal
- Rupture membranes once head or breech of second twin enters pelvis and pushing recommences
- Malpresentation of second twin = C-section
- Fetal distress or cord prolapse = vaginal delivery expedited with a ventouse or breech extraction (general, epidural or spinal anaesthesia)
- Prophylactic oxytocin infusion to prevent PPH
