Multiple Pregnancy

Question 1

Define

Answer 1

Pregnancy involving more than 1 foetus

• RFs: advanced maternal age, IVF, previous multiple pregnancy
• Occurs in 1 in every 80 pregnancies (~1%) – higher chances if IVF
• Hereditary factors

Chorion = number of placentae
Amnion = number of amniotic sacs
Monozygous – division of fertilised egg à IDENTICAL – 20% of twins

• 25% split 0-4 days à dichorionic diamniotic à 2 placenta and 2 amniotic sacs

S/S: λ sign

• 75% split 4-8 days à monochorionic diamniotic -> 1 placenta (share), 2 amniotic sacs
• S/S: T-sign

1% split 8-12 days à monochorionic monoamniotic à 1 placenta (share), 1 amniotic sac (share)

S/S: T-sign, ‘entangled cords’
- <1% split >12 days à conjoined twins
- Dizygous – fertilisation of 2 ovum by 2 different sperm à NON-IDENTICAL – 80% of twins

o DCDA – separate placentae, amnions, chorions

Question 2

Gestational Age and Chorionicity:

Answer 2

Gestational Age and Chorionicity:

Gestational Age

• Offer 1st trimester USS when CRL 45-84 mm (11-13+6 weeks) to determine: EGA, chorionicity, and to screen for Down syndrome (use largest baby to estimate gestational age)
• Chorionicity – refers to the type of placentation (this is the most important feature to an obstetrician)
• Detect at time of detecting twin/triplet pregnancy by USS using number of placental masses, lambda (dichorionic) or T-sign (monochorionic) and membrane thickness

· Examine junction between the inter-fetal membrane and the placenta

· In DC pregnancies à triangular placental tissue projection (λ sign) into base of the membrane

· In MC pregnancies à no placental tissue projection (T-sign) into the base of the membrane

• If presenting after 14 weeks, determine chorionicity using all of membrane thickness, lambda sign, number of placental masses and disconcordant foetal sex

Question 3

Signs and symptoms

Answer 3

Signs & symptoms (asymptomatic): FH = Foetal Heartrate

o 1st trimester à incidental on USS, hyperemesis – increased βHCG

o 2nd trimester à large for dates, multiple parts on abdominal exam

o Abdominal exam à increased SFH, multiple parts, >1 FH

Question 4

Management

Answer 4

Antenatal:

• FBC at 20-24w -> query extra supplementation of iron or folic acid, and repeat at 28 weeks
• BP (increased chance of eclampsia) TTTS Monitoring / Growth Scans
• GTT (increased likelihood of diabetes) 16w (every 2w) for shared placenta pregnancies

20w (every 4w) for no shared placenta pregnancies
- Serial USS for foetal growths
- Monochorionic twins: scan at 12, 16 and every 2 weeks until delivery SHARED
- Dichorionic twins: scan at 12, 20 and every 4 weeks until delivery NO SHARING
- Monochorionic triplets: scan at 12, 16 and every 2 weeks until delivery SHARED
- Dichorionic triplets: scan at 12, 16 and every 2 weeks until delivery SHARED
- Trichorionic triplets: scan at 12, 20 and every 4 weeks until delivery NO SHARING
- TTTS screening = 16-24 weeks (every 2 weeks) – if shared placenta
- General growth scans = after 24w (every 2 or 4 weeks)

Specialist Care:

• Uncomplicated monochorionic diamniotic twin pregnancy should be offered at least 9 appointments with a healthcare professional, at least 2 should be with a specialist obstetrician
• Uncomplicated dichorionic twin pregnancy should be offered at least 8 appointments and at least 2 with a specialist obstetrician
• Uncomplicated monochorionic triamniotic or dichorionic triamniotic pregnancy should be offered at least 11 appointments and at least 2 with a specialist obstetrician
• Uncomplicated trichorionic triamniotic triplet pregnancy should be offered at least 7 scans and at least 2 with a specialist obstetrician

Pre-term birth (60% of twin pregnancies):
- Preventing Preterm Birth – do NOT use the following routinely to prevent spontaneous preterm birth:
- Bed rest at home or in hospital IM or vaginal progesterone

Cervical cerclage
Oral tocolytics
Corticosteroids -> will be useful if preterm birth is likely (should be targeted)

Timing of birth:
- 60% of twin pregnancies result in spontaneous birth before 37 weeks
- Offer continuous foetal monitoring (CTG); if needed: scalp electrode and foetal blood monitoring
- Offer elective birth if (if declined à weekly obstetrician appointments):
- Uncomplicated monochorionic twin – from 36 weeks (after course of steroids)
- Uncomplicated dichorionic twin – from 37 weeks
- Uncomplicated triplet – from 35 weeks (after a course of steroids)

Vaginal delivery (first twin is in the cephalic position; 2nd may be breech but this is ok)

· Second breech baby can be turned using Internal Pedalic Version (IPV)

Question 5

Complications

Answer 5

Foetal Complications:

• IUGR (and discordant IUGR: when one baby is SGA and the other normal or LGA)

· Monitored with EFW discordance (not SFH) à difference in size >20% is an indicator of IUGR

· Aim to repeat scans at least every 4 weeks

• Down Syndrome (greater absolute risk as same risk PER baby so increased TOTAL risk)
• Structural Abnormalities (2x in monozygotic babies)
• Twin-to-Twin Transfusion Syndrome (TTTS)
• Intra-uterine death (IUD)

· For dizygotic twins, the other twin will be fine

· In monozygotic twins that share a placenta (monochorionic), this can be bad as the BP will drop in the surviving twins’ placenta à neurological damage in the surviving twin in 25%

Maternal Complications:

• Pre-eclampsia (more risk of abnormal vasculature development)

· Always check at every antenatal appointment

· Follow normal pre-eclampsia pathways

• Hyperemesis gravidarum (more bHCG)
• GDM (more placental lactogen and placental steroids so more likely to tip into diabetes)
• APH, PPH (stretched uterus)
• Anaemia and thrombocytopaenia (more required to sustain the two children)

Question 6

Management of comp

Answer 6

TTTS – occurs in MONOCHORIONIC pregnancies…

Symptoms – sudden abdomen size increase, SOB

· Start diagnostic monitoring with USS from 16-24 weeks on a 2-weekly basis

· Delivered by 34-37 weeks

Management:

· Old treatment à amnioreduction

· New treatment (<26w) à foetoscopic laser ablation of vascular anastomoses

· New treatment (>26w) à delivery

Pathogenesis = direct arterial to venous flow in placenta

· Donor baby SGA / oligohydramnios

· Recipient baby LGA / polyhydramnios

· Diagnosed if >25% difference of EFW

· Risk to recipient baby > donor baby:

• More blood…
• More cardiac strain…
• Hydrops fetalis
• Selective Growth Restriction / disconcordant IUGR:

Selective reduction may be an option if it is early

Surveillance scans every 2 weeks

Abnormal Doppler waveforms = indication for delivery