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In this research study, the investigators want to learn more about the safety and effectiveness of a fetal surgery, known as fetoscopic laser photocoagulation (FLP), for the treatment of a pregnancy condition called vasa previa (VP). Vasa previa is a pregnancy complication that happens when blood vessels from the fetus grow over the entrance to the womb. In a VP pregnancy, natural vaginal birth is deadly for the baby in more than half of cases due to the bursting of VP vessels and severe blood loss. Currently, VP patients are recommended to be closely monitored and often hospitalized once they reach the third trimester of pregnancy. An early delivery by C-section would typically be performed in order to avoid breaking the exposed fetal vessels. Fetoscopic laser photocoagulation is a minimally invasive surgery in the womb to remove or correct abnormal blood vessels and tissues. In the FLP procedure, the surgeon uses a fetoscope (a tiny telescope) and a laser device to seal off unprotected vessels. While this surgery has been used to treat other pregnancy conditions, it has not yet been proven to be safe and/or effective for the treatment of vasa previa. This treatment aims to eliminate the VP, and, if successful, may have the potential to minimize the risk of bleeding, thereby enabling patients to avoid long hospitalization before delivery. This procedure may enable VP patients to have a vaginal delivery instead of C-section.


Vasa Previa, Pregnancy Complications, Maternal; Procedure, In Utero Procedure Affecting Fetus or Newborn

Recruitment Status

Not yet recruiting

Eligibility Criteria

Inclusion Criteria:

Pregnant patient
Singleton pregnancy
Confirmed diagnosis of vasa previa, defined as unprotected fetal vessels running through the membranes at or within 5cm of the internal cervical os. Diagnosis must be confirmed after 26w0d, and before 32w5d
Able to undergo intervention during 30w0d to 32w6d
Type II vasa previa in which one placental lobe is considered to be accessory, defined as constituting less than 20% of the total placental mass seen on MRI and US imaging
Type II vasa previa in which multiple bridging vessels connect the two placental lobes (≥4 vessels), and only 1-2 vessel(s) run through or within 5cm of the internal cervical os
Patient is eligible to undergo anesthesia
Patient and biological father of the fetus (if available) are able to provide signed informed consent

Exclusion Criteria:

Gestational age at referral higher than 32w6d
Multiple pregnancy
Vasa previa types I and III
Type II vasa previa in which the accessory lobe constitutes more than 20% of the total placental mass, as determined by the fetal surgeon during diagnostic fetoscopy
Type II vasa previa in which all of the bridging vessels between placental lobes are running over the internal cervical os
Fetal growth restriction, defined as estimated fetal weight or abdominal circumference less than the 10th percentile for gestational age
Abnormal fetal brain MRI, including delayed maturation, hemorrhage, arterial ischemic injury, abnormal ventricular size, or any congenital anomalies
Allergy or previous adverse reaction to ancillary medications with no available alternative
Preterm contractions and PPROM before surgery
Preeclampsia or uterine anomaly during the current pregnancy
Placenta previa, low-lying placenta, placenta accreta spectrum disorder
Suspicion of major recognized congenital syndrome on ultrasound or MRI that is not compatible with postnatal life
Maternal pre-pregnancy BMI >40
Active hepatitis B, hepatitis C, or HIV infection
High risk for congenital fetal bleeding disorders
Unreliable pregnancy dating due to an irregular menstrual cycle/uncertain last menstrual period with no confirmed dating from first trimester ultrasound
The surgeon determines that the procedure is not feasible for any other reason after diagnostic fetoscopy


Intervention Type

Intervention Name


Fetoscopic Laser Photocoagulation


Not Applicable



Min Age

18 Years

Max Age

55 Years

Download Date

March 12, 2024

Principal Investigator

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Primary Contact Information

Brittany E. Gudanowski

This field has been modified from to show a contact specific to Boston Children's.

For more information on this trial, visit


For more information and to contact the study team:

Fetoscopic Laser Photocoagulation in Management of Vasa Previa NCT06290232 Brittany E. Gudanowski