Review Note

Last Update: 03/27/2025 09:26 PM

Current Deck: ACG Part 2::Obstetrics

New Card (Unpublished)

Currently Published Content

Front

Back

No published tags.

Pending Suggestions

Field Change Suggestions:

Front

Commit #309758

SS_OB 1.34 Discuss the anaesthetic management of problems that may arise with labour and delivery, including the following situations:
- Multiple gestation

Back

Commit #309758

Multiple Gestation

Type
- Increasing incidence of twin births between 1980 to 2010 due to:
  - 1/3 delayed childbearing and spontaneous twinning
  - 2/3 assisted reproductive technologies
- Monozygotic twins – single fertilized ovum divides into 2 individuals (4/1000 births)
- Dizygotic – 2 separate ova are fertilized (incidence varies among races and increases with maternal age and parity)

Placentation

Type of placentation determines the likelihood of arteriovenous vascular anastomoses/communications, which are common in monochorionic placentas and rare in dichorionic.

Vascular anastomoses may result in twin-to-twin transfusion syndrome and intrauterine fetal death.

Dichorionic diamniotic
- Occurs in all occurrences of dizygotic twins.
- Also if monozygotic twinning occurs during the 2-3 days after fertilization.

Monochorionic diamniotic
- If cleavage occurs between 3-8 days.

Monochorionic monoamniotic
- If cleavage occurs between 8-13 days.

Conjoined twins
- If embryonic cleavage occurs between 13-15 days.

Maternal physiologic changes

Multiple gestation exaggerates the physiologic and anatomic changes of pregnancy.

CVS and pulmonary changes are greatly affected.

Renal, hepatic, and CNS changes resemble those that occur with a singleton fetus.

Reduction in TLC and FRC due to increased uterine size.

Increase in maternal plasma volume (approx. 750ml).

Relative or actual anaemia.

Thrombocytopaenia.

Increased CO (20% greater), SV (15%), HR (3.5%).

Aortocaval compression and supine hypotension syndrome.

Fetal complications

Related to multiple gestation and abnormal presentation.

Twin-to-twin transfusion
- Increases perinatal mortality rate and risk for adverse neurodevelopment outcome in survivors.
- One twin becomes the donor, one becomes the recipient.
  - Donor twin is smaller and at risk for IUGR and anaemia.
  - Recipient twin is plethoric and at risk for volume overload and cardiac failure.

Fetal growth restriction
- Can be due to:
  - Twin-to-twin transfusion.
  - Polyhydramnios in 1 fetal sac, which may limit the growth of the other fetus.
  - Limited intrauterine size.
  - Uteroplacental insufficiency.
  - Chromosomal abnormalities.

Preterm labour
- Higher incidence in women with twins resulting from IVF (52%) compared with spontaneous twins (22%).
- 60% of women with twins deliver before 37/40.
- 6.4% of women with triplets reach term.

Abnormal presentation – vertex, breech, and/or transverse lie; increases risk for umbilical cord prolapse.

Fetal morbidity and mortality (3x greater in twin pregnancies compared to singleton pregnancies).

Congenital anomalies

Polyhydramnios

Cord entanglement

Umbilical cord prolapse

Maternal complications

ACOG: “Women with multiple gestations are nearly 6 times more likely to be hospitalized with complications, including preeclampsia, preterm labor, preterm premature rupture of membranes, placental abruption, pyelonephritis, and postpartum hemorrhage.”

Incidence of maternal complications increases in proportion to the number of fetuses.

Preterm premature rupture of membranes

Preterm labour

Prolonged labour

Pre-eclampsia/eclampsia

Placental abruption

Disseminated intravascular coagulation

Operative delivery (forceps and caesarian).

Uterine atony – increased risk due to uterine distension.

Obstetric trauma

Antepartum and/or postpartum haemorrhage – approx. 500ml greater in multiple gestation pregnancies than in singleton pregnancies.

Gestational diabetes

Pulmonary oedema

Peripartum hysterectomy

Anaesthetic management

Pre-op:
- Early pre-anaesthesia evaluation and assessment.
- Offer epidural if for vaginal delivery.
  - May be at increased risk for aortocaval compression and hypotension.
  - Enables provision of anaesthesia for emergency LSCS.
- Large IV access.
- Bloods – FBE, coags, G&H.
- Prepare for complications.
- LSCS is likely as multiple gestation pregnancies are associated with higher incidence of caesarian delivery.
  - Most obstetricians favour caesarian delivery for all patients with 3+ fetuses.
  - Prolonged uterine incision-to-delivery interval due to longer time required to deliver multiple infants à umbilical cord acidaemia and neonatal depression.
  - Nonparticulate antacid should be administered at first sign of obstetrician concern or before proceeding to the operating room as increased uterine size à increased risk for pulmonary aspiration of gastric contents.

Neuraxial:
- 2 twins have similar umbilical cord blood pH measurements.
- Epidural during labour and vaginal delivery.
- Preference for epidural vs single short spinal anaesthesia due to:
  - Spinal:
    - Lack of flexibility in cases of rapidly changing conditions.
    - Potential increased incidence of high spinal anaesthesia, with small increase in cephalad spread of neuroblockade (2 dermatomes).
  - Epidural:
    - Gradual onset of sympathetic blockade, which reduces the incidence of severe hypotension.
- Increased fetal uptake of epidural LA in twin pregnancy – higher concentrations of LA in twin newborns compared to singleton newborns (35-53%) exposed to epidural anaesthesia à possible neonatal depression.

If GA is required:
- GA – second twin is more acidotic than the first.
- Decreased FRC and increased maternal weight à hypoxaemia develops more rapidly during periods of hypoventilation or apnoea.
- Increasing maternal weight (at a greater rate after 30 weeks gestation) à may increase risk for difficult tracheal intubation and ventilation.