MULTIPLE PREGNANCY Flashcards by

What is the incidence of twin pregnancy?

1 in 80 pregnancies

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What is the incidence of spontaneous triplets?

1 in 6400 pregnancies

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What factors increase the likelihood of having a multiple pregnancy?

Increasing maternal age

Increasing parity

More common in African

Improved nutrition

Assisted conception

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How and when are multiple pregnancies usually diagnosed?

Routine dating ultrasound scan at 11-14 weeks

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What percentage of twins are dizygotic?

75%

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What is the most important clinical issue to work out on discovery of twins?

The chorionicity of the pregnancy

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What is chorionicity?

How many placenta there are for the twins - ie whether they are sharing or not.

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What is the risk of monochorionic twins?

Unequal distribution of blood leading to growth restriction of one twin and macrosomia in the other

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Are monochorionic twins always monozygotic?

Yes.

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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.

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Are most triplets monozygotic or trizygotic?

Neither. Most triplets come from originally two fertilised ova, where one of them splits to form monozygotic twins.

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How do work out the chorionicity antenatally?

USS before 16 weeks gestation

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What is the name of the sign seen on USS in dichorionic twins?

Lambda

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What is the name of the sign seen on USS in monochorionic diamniotic twins?

T sign

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How might you work out the zygosity of twins on USS?

Chorionicity

Different sexs

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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?