Twin Pregnancy

Last updated 21.11.12

 

Index

 

Definition

-  Pregnancy with two fetuses

 

Features

-  Overall 1-2% incidence

-  1.25% of spontaneous pregnancies

-  60% of twins DCDA (2 ovum)

-  Clomiphene (Clomid) accounts for 7% of all twin pregnancies

-  IVF accounts for 20% of all twin pregnancies

-  1:250 pregnancies monozygotic twins (stable incidence)

-  Increases with maternal age

-  Associated w higher Beta HCG levels

-  Increased iron requirements

-  Chorionicity determines management

 

Classification

- Causes

-  Double ovulation (dizygote) 2/3 twins

-  Division of single zygote (monozygote) 1/3 twins

- Nomenclature

-  Number of zygotes (fertilized ova) = monozygotic (1) or dizygotic (2)

-  Number of placentae = monochorionic (1) or dichorionic (2)

-  Number of amniotic sacs = monamniotic (1) or diamniotic (2)

- Placentation

-  Male & female = always dizygotic & dichorionic

-  Same sex = dizygotic or monozygotic & dichorionic or monochorionic

-  Monochorionic = always same sex

-  Monozygotic = always same sex

-  Must determine chorionicity by end 1st trimester

-  Determines Mx

- Dizygotic must be dichorionic & diamniotic (DCDA)

- Monozygotic may have variation of placenta (chorion) & amniontic sac (amnion)

-  Dichorionic Diamniotic (DCDA)

-  All dizygotes, 30% monozygotes

-  Division in 1st 2 days

-  8-9% mortality

-  Monochorionic Diamniotic (MCDA)

-  70-80% monozygotes

-  Division 4-8 days

-  25% mortality

-  30% complication rate

-   TTT Syndrome 15%

-   TAPS

-   Selective IUGR 15%

-   Isolated disconcordant growth

-   Congenital defects

-  Monochorionic Monoamniotic (MCMA)

-  1% monozygotes

-  Division 8-12 days

-  50-60% mortality

-   Usually from cord entanglement

-  TTT Syndrome

-  Conjoint twins

-  Division >12 days, after primitive streak

 

 

Complications

- Increased abnormalities: chromosomal (not for ART)

-  Minor 4%, major 2%

- Shoulder dystocia

- Increased miscarriages

- Vanishing twin syndrome 20-60% of twin conceptions

- HTN, pre-eclampsia, anaemia, GDM

- APH & PPH

- Preterm delivery

- PPROM

-  10% at <28/40

-  50% at <37/40

- IUGR

-  50% at 38/40

- LUSCS & instrumental delivery

- TTT syndrome

- Uterine atony

 

Associated S/S

-  More S/S of pregnancy

-  Increased hyperemesis gravidarumSize > dates on fundal height

-  >5cm compared to singleton at same gestation

-  Multiple poles palpated on abdo exam

 

Mx

- Antenatal

-  US 12/40: chorion & amnion

-  First trimester best time to determine chorionicity (up to 100% sens)

-   Second trimester upto 90% sens (up to 97% if 3D)

-  T sign: MC

-  Lambda sign: DC

-  Membrane thickness >2mm: DC

-  Disconcordant genders: DC

-  Corpus luteum count

-  Screening for aneuploidy

-  Increased NT may indicate TTT

-  Serum not helpful as does not show which fetus effected

-  Nutritional support

-  Iron

-  +/- Ca

-  Increased calories

-  Regular antenatal visits

-  Selective termination

-  Prevention of survival of an anomalous fetus..

-  NOT the same as selective reduction

- Delivery

-  Elective LUSCS vs NVD

-  If vertex & vertex: NVD

-  If vertex & non-vertex

-   2nd twin 1500-3600g: NVD

-   Else LUSCS

-  Nonvertex 1st: LUSCS

-  Experienced obstetrician, paediatrician, aneasthetist

-  Fetal Scalp Electrode (FSE) w continuous FHR monitoring

-  IV access & Group & Hold

-  Epidural preffered analgesia

-  Syntocinon infusion: 40 IU over 4 hrs

 

 

 

References

 

Pic: en.wikipedia.org/wiki/File:Placentation.svg