MULTIPLE PREGNANCY

Multiple pregnancy is an important obstetrical risk factor for fetal loss or neonatal morbidity/mortality, with an incidence of ~1:80 livebirths (for twins) and ~ 1:1000 (for triplets), in India.

Types: Multiple pregnancies may be:

• Polyovular (Dizygotic), with release and fertilization of two (or more) different ova at the same time, each with its own chorion and amnion (dichorionic, diamniotic). Dizygotic twins are of different sex and blood group in 50% cases.

• Mono-ovular (Monozygotic), with fertilization of a single ova but splitting of blastocyst in early phase to develop separately as two fetus. 75% of monozygotic twins share common chorion (monochorionic), though almost all of them have separate amnion (diamniotic). Monozygotic twins are essentially of same sex, blood group and grossly similar, if not identical, features. Splitting of blastocyst in late stages may lead to con­joined or Siamese twins (~1:50,000 live births), which are usually females and joined to each other at thoraco/ abdominal region (thoraco/omphalopagus; commonest), head (craniopagus, rarest) or other sites (incomplete duplication).

Risk factors: While risk factors for mono-ovular multiple pregnancies are unclear, poly-ovular pregnancies are more common in: (a) elderly or multiparous mothers, (b) family history of multiple pregnancy, (c) conceptions after infertility interventions, and (d) women with high gonadotropin levels.

Complications: Apart from frequent abortions or stillbirths, multiple pregnancies are associated with ~3-4 times higher risk of neonatal mortality/morbidity due to various complications (Table 12.5), most important being twin-to-twin transfusion.

Twin-to-twin transfusion (Fetal transfusion syndrome) mainly occurs in monochorionic twins, due to common placenta. Artery from one fetus (donor) may acutely or chronically deliver blood into vein of other fetus, leading

TABLE 12.5: Complications of multiple pregnancies

• Due to uterine overcrowding

- Low birth weight

- Prematurity

- Positional deformities, e.g. CDH

• Due to shared blood supply

- Twin to twin transfusion

- Intrauterine hypoxia

- Vascular anomalies

• Obstetrical problems

- Polyhydramnios

- Abnormal placenta/antepartum hemorrhage

- Premature rupture of membranes

- Abnormal lie (obstructed labor)

• Postnatal complications

- Birth asphyxia

- Severe anemia in donor twin

- Polycythemia in recipient twin

- Hypoglycemia

- Respiratory distress syndrome

CDH: Congenital dislocation of hip to severe anemia, hypovolemia and low birth weight in the donor and plethora, polycythemia, hypervolemia and hydrops in the recipient. Generally, a difference of gt;5% in Hb and 20% in weight between two fetuses indicates twin-to- twin transfusion. Death of the donor fetus generates plenty of fibrin thrombi, which may be passed-on to surviving fetus with consequent DIC.

Management of multiple pregnancies involves early prenatal diagnosis and timely referral to equipped centers. Selective fetal reduction with transabdominal injection of potassium chloride may be required in numerous multiple gestations (3 or more).

Postnatally, all twins should be closely monitored till 24-48 hours for late problems, e.g. hypoglycemia, respi­ratory distress, anemia, polycythemia, etc. Twin-to-twin transfusion may require immediate blood transfusion to the donor and partial exchange in the recipient.

Prognosis: Although perinatal mortality is ~4-times higher in twins, survival among live born twins is relates to birth weight and gestation (comparable with singletons). Usually, first-born twin is smaller and at- risk for hypoglycemia while second twin has higher risk of birth asphyxia and respiratory distress syndrome. Concordant illnesses, e.g. hyaline membrane disease or infections are common in twins and the weight difference tends to disappear by 4-6 month of age.

12.4