Selective Intrauterine Growth Retardation in Monochorionic Twins:
Information for Healthcare Providers

Selective intrauterine growth retardation (IUGR) occurs in approximately 12.5-25% of all monochorionic pregnancies, and is associated with an increased perinatal mortality rate. Spontaneous demise of the IUGR twin may result in concomitant demise of the appropriately grown (AGA) twin in up to 40% of cases, or in neurological damage of the AGA twin in up to 30% of cases. The adverse effects of the spontaneous demise of the IUGR twin on the AGA twin are the result of post-mortem feto-fetal hemorrhage from the AGA to the IUGR twin through placental vascular communications. Such complications are not seen in dichorionic twins.

Diagnosis

Selective IUGR of one twin is defined as an estimated fetal weight below the 10^th percentile for gestational age. Monochorionicity is established sonographically by the presence of a single placenta, similar external genitalia, thin dividing membrane and absence of a "twin peak" sign. Differential diagnosis with TTTS is made by the lack of combined severe oligohydramnios (maximum vertical pocket, MVP, of amniotic fluid <2 cm in the IUGR twin with polyhydramnios in the AGA twin (MVP >8 cm).

Treatments

Current treatment of IUGR in monochorionic twins involves either expectant management and early delivery if warranted, termination of pregnancy, or umbilical-cord occlusion. We developed a selective laser technique for the treatment of twin-twin transfusion syndrome (TTTS) that allows precise obliteration of the vascular anastomoses between the fetuses, while sparing normally perfused areas of the placenta (selective laser photocoagulation of communicating vessels, or SLPCV). By unlinking the fetal circulations and preserving areas of the placenta that belong to each twin, this surgical technique essentially transforms a monochorionic pregnancy into a "functional dichorionic" gestation.

We have performed a preliminary study comparing the outcomes of patients with monochorionic twin pregnancies with selective IUGR managed expectantly vs. patients treated with SLPCV. The results of that study showed that placental anastomoses can be obliterated in these patients and that there was a trend toward decreased neurological morbidity in the laser group of fetuses treated with SLPCV.

We are currently conducting a randomized clinical trial, expectant management vs. laser treatment of monochorionic twins with severe selective intrauterine growth retardation and absent or reverse diastolic flow in the umbilical artery. For more information, click here www.USFetus.org

In Utero Fetal Weight Standards at Ultrasound
Percentiles (g)

(adapted from Hadlock et al, 1991)

Referrals

You may download the IUGR evaluation form or contact us to fax the form to your office. For further information, feel free to contact us.

Phone Toll Free: 1-877-FETAL-77
Phone: 813-259-8513
Fax: 813- 259-0839
Email: sdzabel@tgh.org 

REFERENCES:

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