Multiple Pregnancy Flashcards
Locked twins
occur when the after-coming head of the first breech fetus is locked with the head of the second cephalic fetus.
Di-chorionic twins US F/U:
US should be done at 24, 28, 32 and 36 wks
Mono-chorionic twins US follow-up:
US should be done every 2 wks until delivery at 16, 20, 22 and 24.
Complications which occur only in monochorionic twin pregnancy include
TTTS, TAPS, TRAP sequence, monoamniotic pregnancy and conjoined twinning.
Percentage of monochorionic among twin pregnancies
One third
TTTS earliest sign:
The ‘donor’ twin has a DVP of < 2 cm (oligohydramnios) and the ‘recipient’ twin has a DVP > 8 cm (polyhydramnios).
the diagnosis of polyhydramnios is made when DVP ≥ 8 cm at ≤ 20 weeks and ≥ 10 cm after 20 weeks’ gestation.
TTTS percentage
TTTS affects 10 – 15% of monochorionic twin pregnancies and is associated with increased perinatal mortality and morbidity; if untreated, it leads to fetal demise in up to 90% of cases, with morbidity rates in survivors of over 50%
The success rate of TTTS Management:
fetoscopic laser ablation, which significantly improves the prognosis. Laser treatment in these pregnancies results in 60–70% double survival and.
In monochorionic twin pregnancy, screening for TTTS should start at
16 weeks, with scans repeated every 2 weeks thereafter
Quintero staging
I Polyhydramnios-oligohydramnios sequence: DVP>8cm in recipient twin and DVP<2cm in donor twin
II Bladder in donor twin not visible on ultrasound
III Absent or reversed umbilical artery diastolic flow, reversed ductus venosus a-wave flow, pulsatile umbilical venous flow in either twin.
IV Hydrops in one or both twins
V Death of one or both twins
Treatment of TTTS
• Laser ablation is the treatment of choice for TTTS at Quintero stages II and above (GRADE OF RECOM- MENDATION: A).
• Conservative management with close surveillance or laser ablation can be considered for Quintero stage I (GRADE OF RECOMMENDATION: B).
• When laser treatment is not available, serial amnioreduction is an acceptable alternative after 26 weeks’ gestation (GRADE OF RECOMMENDATION: A).
If conservative management is chosen for Quintero stage I, worsening poly- hydramnios, maternal discomfort and shortening of the cervical length are considered ‘rescue’ criteria signalling a need to proceed with fetoscopic laser treatment.
In a systematic review of the management of Stage 1 TTTS pregnancy, overall survival appeared to be similar for those undergoing laser therapy or conservative management (85% and 86%, respectively), but was somewhat lower for those undergoing amnioreduction (77%)
The risk of recurrence of TTTS and occurrence of TAPS is reduced by use of the Solomon technique (equatorial laser dichorionization) compared with the highly-selective technique
A common practice is weekly ultrasound assessment for the first 2 weeks after treatment, reducing to alternate weeks following clinical evidence of resolution
The prenatal diagnosis of TAPS is based on
the finding of discordant MCA Doppler abnormalities
The incidence of TAPS occurring spontaneously in MCDA twins is up to
5%
However, it may complicate
96 up to 13% of cases of TTTS following laser ablation
The criteria for TAPS diagnosis postnatal:
include a difference in hemoglobin concentration between the twins of more than 8 g/dL and at least one of either reticulocyte count ratio greater than 1.7 or small vascular anastomoses (< 1 mm in diameter) in the placenta
The prenatal diagnosis of TAPS is based on
the finding of discordant MCA Doppler abnormalities, including MCA-PSV > 1.5 multiples of the median (MoM) in the donor, suggesting fetal anemia, and MCA-PSV < 1.0 MoM in the recipient, suggesting polycythemia.
The polycythemic twin might have a ‘starry sky’ appearance of the liver pattern due to diminished echogenicity of the liver parenchyma and increased brightness of the portal venule walls.
Additional ultrasound findings in TAPS include differences in placental echogenicity and thickness, with a bright, thickened section associated with the donor and an echolucent thin section associ- ated with the recipient.
Antenatal and postnatal staging of twin anemia– polycythemia sequence (TAPS)
Stage Antenatal staging
1 Donor MCA-PSV > 1.5 MoM and recipient MCA-PSV < 1.0 MoM,
without other signs of fetal
compromise / Hb diff (g/dL)
> 8.0
2 Donor MCA-PSV > 1.7 MoM and
recipient MCA-PSV < 0.8 MoM, without other signs of fetal compromise / > 11.0
3 Stage 1 or 2 and cardiac compromise in donor (UA-AREDF, UV
pulsatile flow, or DV increased or
reversed flow)
4 Hydrops of donor twin
5 Death of one or both fetuses, preceded by TAPS
Postnatal staging: intertwin
> 14.0
17.0 > 20.0
TAPS screening and management
to screen for TAPS, the MCA-PSV should be measured from 20 weeks onwards in both fetuses, and during the follow-up of cases treated for TTTS. Prevention of TAPS by modifica- tion of the fetoscopic laser ablation technique remains the best way to prevent morbidity
Treatment options for Twin reversed arterial perfusion (TRAP)
• The chances of survival of the pump twin are increased by the use of minimally invasive techniques (e.g. cord coagulation, cord ligation and photocoagulation of the anastomoses, as well as intrafetal methods), preferably before 16 weeks of gestation
Percentage of TRAP
is a rare complication of mono-
chorionic twin pregnancy (1% of monochorionic twin
pregnancies and 1 in 35000 pregnancies overall).
Monochorionic pregnancy optimum US follow up
Fetal ultrasound assessment should take place every 2 weeks in uncomplicated monochorionic pregnancies from 16+0 weeks onwards until delivery
(RCOG)
• Incase of demise of one fetus of twins in MCDA or MCMA what steps should be taken ?
Esp.(post-laser),brainimaging of the surviving cotwin should be considered 4–6 weeks later, and neurodevelopmental assessment should take place at 2 years of age
The outcome of the monozygotic twinning process depends on when division occurs if zygote divide
*Within 72 hrs after fertilization: two embryos (di-di) morula stage
* If happen btw 4-8 days: diamniotic monochorionic twin blastocyst stage
*btw 8-12 days: mono-mono at implanted blastocyst
* more than 13 days: conjoined twins at formed embryonic cyst
The incidence of pregnancy-related hypertension in women with twins is
20%
Recipient twin complications in TTTS:
- circulatory overload and heart failure
- hypervolemia and hyperviscosity and occlusive thrombosis
- polycythemia that may leads to severe hyperbillirubinemia and kernicterus.
The prevalence of TTTS approximates
1-3 cases per 10000 births (SMFM,2013)
The two diagnostic criteria of TTTS diagnosis:
1- monochorionic diamnionic pregnancy
2- hydramnios defined by a largest vertical pocket >8 cm in one sac and oligohydramnios defined by largest vertical pocket < 2 cm in the other twin.