The purpose of this study is to evaluate whether the entry technique surgeons use to get inside the uterus to perform fetoscopic laser photocoagulation for twin-to-twin transfusion syndrome has an effect on the rates of chorioamniotic membrane separation.

Patients who choose to undergo fetoscopic selective laser photocoagulation (SFLP) at Texas Children's Fetal Center will be offered participation in this research study by study investigators. Description of study rationale and design and a focused interview by the study coordinator to afford potential participants a formal opportunity to examine what they have learned about the research study in the course of their evaluation and discuss how they feel about enrolling in the research study. Once the patient is deemed eligible the informed consent process will be reviewed. If patients elect to participate in the study, informed consent will be obtained, and participants will be provided a copy of the signed consent.

After consent has been obtained, participants will be randomized into two groups ("direct entry" and "Seldinger technique").

Procedure: Selective laser photocoagulation (SFLP) is standard of care for the treatment of complicated monochorionic twin pregnancies. Entry into the uterus for SFLP is achieved under ultrasound guidance using one of two accepted methods, direct entry or the Seldinger technique. Intravenous sedation with local anesthesia at the site of insertion has been found to provide sufficient maternal anesthesia for the procedure.

Group I - Direct entry: The surgeon will gain access to the uterus by inserting a sharp trocar through a small incision in the skin. After access has been established, the trocar is removed and a small tube called a cannula is left in place.

Group II - Seldinger technique: The surgeon will gain access to the uterus by inserting needle through a small incision in the skin and run a guide wire through the needle so a thin tube called a cannula can be placed over the wire.

Follow-Up:

Participants will be monitored after the procedure and upon discharge from the hospital they are free to resume care with their primary doctor. Investigators will collect follow-up data on the health of the participant and the babies until the babies turn one month old.

Inclusion Criteria:

• Patients who are eligible and elect to undergo fetoscopic selective laser photocoagulation for complicated monochorionic-diamniotic twin pregnancies with twin-to-twin transfusion syndrome.
• Patients will be between 16 0/7 weeks and 26 0/7 weeks gestational age.

Exclusion Criteria:

• Patients who do not elect to undergo fetoscopic laser photocoagulation for the treatment of complicated monochorionic-diamniotic twin pregnancies with twin-to-twin transfusion syndrome.
• Triplets and higher order multiple gestations.
• Patients who are less than 16 0/7 weeks or greater than 26 0/7 weeks gestational age.
• Patients with a short cervix (less than 1.5 cm).
• Patients with a known subchorionic hemorrhage.