Multiple pregnancy Flashcards
Define chronicity and zygosity and identify the different types of twin pregnancy
Chorionicity - refers to the number of chorions that surround the foetuses and corresponding placentation
Zygosity - refers to the number of eggs fertilised, whether it is one egg cell which divides early in development or two seperate eggs which are released and fertilised at the same time due to hyperovulation
Dichorionic Diamniotic (DCDA) - Monozygotic or dizigotic, if monozygotic divide 2-3 days after fertilisation, two seperate zygotes which develop two seperate amnions, chorions and palcenta (or placenta can be fused)
Monochorionic diamniotic (MCDA) - Monozygotic divide 3-8 days after fertilisation, fetus’ share one chorion and therefore one placenta, but have seperate amnions.
Monochorionic Monoamniotic (MCMA) - Monozygotic divide 8-13 days after conception, fetus share one chorion, placenta and amnion
Describe the abdominal palpation findings for sarah at 26 weeks compared to a singleton pregnancy
- uterine tightness
- 2x
Describe the complications associated with twin pregnancies, differentiate these according to type of twin pregnancy
perinatal mortality or morbidity due to
- preterm birth
- FGR
- preeclampsia
- TTTS
- antepartum death of a twin
- higher severity of maternal symptoms
More likely to experience
- miscarriage or FDIU
- anaemia
- PE
- GDM
- congenital abnormalities
- preterm birth
- malpresentation
- PPH
- TTTS in monochorionic twins
- aneuploidy in at least one twin
Continuing pregnancy past 37+6 has an increased risk of stillbirth
DCDA
- 1/25 risk of structural abnormality
- 22% rate of 1 fatal demise in first trimester
MCDA
- 1/15 risk of structural abnormality
- 41% rate of 1 fatal demise in first trimester
- death later in pregnancy associated with higher risk of death/disability of other twin
MCMA
- 1/6 risk of structural abnormality
Complications specific to monochorionic twins
- selective FGR
- TTTS
- twin anaemia polycythemia sequence (TAPS)
- death of one twin –> acute hypotension in co twin = significant implications
Explain the expected management and monitoring/surveillance of the twin pregnancy, based on type of twins
11-14 week date, labelling and chronicity scan
then IF DCDA
- offer 16 week review for pregnancy care and surveillance (no US)
- 20 week growth scan (anatomy, biometry, DVP)
- 24 week growth scale, DVP, doppler
- 28 week foetal growth, DVP, doppler alongside maternal screening for anaemia, blood group antibodies, GDM, Anti D if required
- 32 weeks growth scan, DVP, doppler
- 34 weeks offer review of birth plan (no US) and anti D
- 36 weeks fatal growth, doppler, DVP and PLAN TIMING OF BIRTH
essentially typical 20 week scan, typical 28 and 34 week anti D, with 4 weekly additional growth scans at 24, 28, 32 and 36 weeks. discuss timing of birth at 34 weeks. Plan timing of birth at 36 weeks. Offer elective birth from 37 weeks.
IF MCDA and MCMA
- 16 week fetal growth, DVP and doppler and discuss plans for pregnancy care
- 18 weeks fetal growth, DVP, doppler
- 20 week detailed anatomy biometry, DVP and doppler
- 22 week fetal growth, DVP, doppler
- 24 week fetal growth, DVP, doppler
- 26 week fetal growth, DVP, doppler
- 28 week fetal growth, DVP, doppler, and routine maternal screening for anaemia, blood group antibodies, GDM and anti D if required
- 30 week fetal growth, DVP, doppler
- 32 week fetal growth, DVP, doppler and discuss birth preferences
- 34 weeks fetal growth, DVP, doppler, anti D if required PLAN TIMING OF BIRTH
- 36 weeks fetal growth, DVP, doppler PLAN TIMING OF BIRTH
essentially typical 20 week growth scan, typical 28 and 34 week anti D, with 2 weekly growth scans for duration of pregnancy from 16 weeks. discuss timing of birth at 32 weeks. Plan timing of birth at 34 weeks. offer elective birth from 36 weeks.
DOPPLERS = umbilical artery doppler, and preferably MCA too
IF SGA/FGR suspected through growth discrepancy >20%, or growth or measurements <10centile - increase US frequency and refer
Birth at level 4 or higher facility
if <34 weeks or neonates have low birth weight, level 6
Early referral to LC
Consider low dose aspirin for PE prophylaxis (more likely and progresses quicker)
Anaemia screening and treatment - higher risk of PPH
Vaginal birth safe if
- leading twin cephalic presentation
- no pregnancy complications
- no other obstetric indication for CS
continuous CTG required
second twin presentation may be transverse - may be able to acihieve longitudinal with external version
birth of second twin can wait up to 30 minutes if FHR normal
Prophylaxis for PPH
Corticosteroids recommended when <34 weeks and birth is imminent within next 7 days
Describe the challenges associated with twins in pregnancy, labour, birth and postnatal
Intrapartum management
- use portable US to confirm presentation of twins
- continuous CTG and consider fatal scalp electrode for twin 1 if difficulty tracing
- ensure obstetrics, paeds and anaesthetics are aware
- blood group and hold and FBE
- consider oxytotoic for active management of third stage given high risk of PPH
- after twin 1 birth perform abdominal palp and VE to determine twin 2 presentation. confirm with US
- consider synt if contractions do not stay strong for twin 2
- consider risk of cord prolapse or placental abruption after birth of twin 1
- PPH prophylaxis
- babies immediately checked by paeds due to increased risks
Postnatal
- extra maternal obs due to PPH risk
- lactation support
Explain the underlying physiology leading to twin-twin-transfusion and potential impact on the foetuses
In monochorionic twin pregnancies twins share a placenta, so some of their blood vessels connect, allowing blood to flow between twins. These connections can be arterial venous connections, or arterial arterial conections. Due to the structure of arteries which posess a layer of smooth muscle allowing pulsation, compared to the structure of veins which do not have this capacity, AA connections will support bidirectional flow and an even distribution of blood between twins, whereas AV connections result in a unidirectional flow of blood towards one twin. When there are an uneven amount of AV connections and insufficient AA connections, the twin with more Arteries connected will donate their blood to their twin, and it will not be returned at the same rate. This results in twin/twin transfusion syndrome
hypovolaemia in donor –> renal hypoperfusion –> RAAS –> oliguria and oligohydramnios
Hypervolaemia in recipient –> polyuria and polyhydramnios
Donating twin
- oligohydramnios
- 2cm or less DVP
- anaemia
- hypoxaemic damage to tissue
- FGR
- lack of visible bladder on US
Recipient twin
- polyhydramnios
- 8cm or less DVP
- fluid overload and stress on heart
- macrosomia
describe the protective versus pathological differences of twin-twin transfusion
AA is protective in the sense that if diagnosis is in stage 1 (meet DVP criteria with no other symptoms), the presence of AA can lead to the blood balancing out on its own
AA rates higher in MCMA than MCDA
Management of a woman with TTTS
Mother may present with
- sudden abdominal swelling
- back pain
- tense uterus
- threatened or premature labour
DVP <2cm and >8cm
Management
- referral to maternal fetal medicine specialist
- expectant management if stage 1
- amnioreduction
- fetoscopic laser photocoagulation
-
Education around S+S of TTTS
counseling related to management and prognosis, weighing up risk and benefit
Discussion of potential long term neurological complications after birth
