MULTIPLE PREGNANCY Flashcards
What is the incidence of twin pregnancy?
1 in 80 pregnancies
What is the incidence of spontaneous triplets?
1 in 6400 pregnancies
What factors increase the likelihood of having a multiple pregnancy?
Increasing maternal age
Increasing parity
More common in African
Improved nutrition
Assisted conception
How and when are multiple pregnancies usually diagnosed?
Routine dating ultrasound scan at 11-14 weeks
What percentage of twins are dizygotic?
75%
What is the most important clinical issue to work out on discovery of twins?
The chorionicity of the pregnancy
What is chorionicity?
How many placenta there are for the twins - ie whether they are sharing or not.
What is the risk of monochorionic twins?
Unequal distribution of blood leading to growth restriction of one twin and macrosomia in the other
Are monochorionic twins always monozygotic?
Yes.
Are monozygotic twins always monochorionic?
No. It depends at what stage in cell replication the split occurs.
1/3 happen in the 8 cell stage and these twins will be dichorionic, like dizygotic twins.
2/3 happen days 3-8 and are therefore monochorionic but diamniotic, as the inner mass splits to form two seperate membranes.
A small proportion happen between days 8-13 and are therefore monochorionic monoamniotic.
Are most triplets monozygotic or trizygotic?
Neither. Most triplets come from originally two fertilised ova, where one of them splits to form monozygotic twins.
How do work out the chorionicity antenatally?
USS before 16 weeks gestation
What is the name of the sign seen on USS in dichorionic twins?
Lambda
What is the name of the sign seen on USS in monochorionic diamniotic twins?
T sign
How might you work out the zygosity of twins on USS?
Chorionicity
Different sexs
What are the risks and complications of multiple pregnancies?
Increased risk of any complication associated with singleton pregnancy - gestational diabetes; pre-eclampsia or pregnancy induced hypertension
Increased chance of fetal malformation
Intrauterine growth restriction (IUGR)
Preterm labour
Increased chance of antepartum haemorrhage (placenta abruption and praevia)
Twin-to-twin transfusion syndrome
Increased chance of postpartum haemorrhage
Locked twins
What is the problem of finding fetal abnormalities in only one of the two twins?
Selective fetocide can result in the miscarriage of the apparently normal fetus as well as the abnormal one.
How should antenatal care be increased in mothers with multiple pregnancy?
Serial USS every 2 to 4 weeks to exclude IUGR - especially important with monochorionic placentation.
In what proportion of multiple pregnancies does preterm labour occur?
30%
What can be used as a screening tool to work out likelihood of preterm labour in a woman with multiple pregnancy?
Cervical length screening by transvaginal ultrasound
How might preterm labour be prevented in higher order multiple pregnancies?
Elective cervical suture at the start of the second trimester
How do you manage a woman with multiple pregnancy who goes into preterm labour?
Tocolytics to allow time for steroids to be given to improve lung maturation.
How much more common is pregnancy related hypertension in multiple pregnant women than singleton women?
3 times
Why is pregnancy-induced hypertension so much more common in multiple pregnancy?
Larger size of the placental bed
What is twin-to-twin syndrome?
Blood is shunted across fetal vascular anastomoses, such that the donor becomes anaemic and growth restricted, with oligohydramnios and the recipient becomes fluid overloaded with polyhydramnios.
What is the incidence of twin-to-twin syndrome in monochorionic diamniotic twins?
15%
When does twin-to-twin syndrome usually occur?
In the second trimester
What is the risk of fetal death in untreated twin-to-twin syndrome?
80%
What is the risk of handicap in the surviving twin in twin-to-twin syndrome?
10%
How do we manage twin-to-twin syndrome?
Laser treatment to placental anastomoses (FLAP - fetoscopic laser ablation of the placenta)
Amniodrainage may be appropriate at later gestation
What are the complications of a scenario where one fetus of a set of monochorionic twins has died and how do we manage this?
Puts surviving twin at risk of neurological damage
Puts mother at risk of DIC as thromboplastins are released into the circulation.
Pregnancy can be managed conservatively until surviving twin reaches a gestation with improved likelihood of survival. 80% of surviving twins can be delivered vaginally
How is the delivery of multiple pregnancy managed?
Neonatal unit intensive care facilities
Allow vaginal delivery if normal pregnancy and twin 1 cephalic presentation
IV access / FBC / G+S
Regional anaesthesia - to allow for more manipulation
Continuous CTG monitoring
Fetal scalp electrode to twin 1
IV syntocinon infusion to start after delivery of twin 1
ECV can be used if twin 2 not in longitudinal presentation
IV syntocinon infusion to continue for third stage to reduce PPH
If twin 1 is not in cephalic presentation at labour, how is delivery of multiple pregnancy managed?
Normally c-section
How do we manage higher order multiple pregnancies?
Nearly always c-section
What is locked twins?
Rare complication of vaginal deliveries when first twin is in breech. Aftercoming head of twin 1 is prevented from entering pelvis by head of cephalic presenting twin 2.
How do we manage locked twins?
If first stage of labour: c-section
If second stage of labour: general anaesthesia to allow necessary manipulation
What is selective fetocide and why is it done in higher order multiple pregnancies?
Intracardiac potassium chloride given to one or more fetuses under ultrasound guidance to improve outcome of remaining fetuses.
When is selective fetocide usually performed?
11-14 weeks
What is the procedure-related risk of miscarriage in selective fetocide?
6%
