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Clinical Obstetrics

Poster Session 3

(866) Zygosity-based Twin Pregnancy Outcomes: Insights from SNP-Based cfDNA Screening

Wednesday, February 14, 2024

8:30 AM – 10:00 AM

Location: Prince George's Exhibit Hall CDE, Lower Atrium Level

Primary & Presenting Author(s)

Ruben A. Quintero, MD (he/him/his)

USFetus Research Consortium
Coral Gables, FL, United States

Coauthor(s)

JH

Joseph Hurt, MD, PhD

University of Colorado, School of Medicine
Aurora, CO, United States
Neeta L. Vora, MD

Associate Professor
University of North Carolina
Chapel Hill, NC, United States
Neil S. Seligman, MD,MSCR

Associate Professor, Department of Obstetrics and Gynecology
University of Rochester Medical Center
Rochester, NY, United States
GR

Gerard Reilly, MD

Seven Hills Women's Health Center
Cincinnati, OH, United States
MW

Myra Wick, MD

Mayo Clinic
Rochester, MN, United States
SW

Samuel Wolf, DO

Emerald Coast Obstetrics and Gynecology
Panama City, FL, United States
Maeve Hopkins, MD, MA

Cleveland Clinic
Rocky River, OH, United States
TW

Tom Westover, MD

Capital Health
Trenton, NJ, United States
Homa K. Ahmadzia, MD, MPH

Assistant Professor
George Washington University
Washington, DC, United States
CK

Camille Kanaan, MD

Eastern Virginia Medical School
Norfolk, VA, United States
Andrei Rebarber, MD

Clinical Professor, Ichan School of Medicine at Mount Sinai
Icahn School of Medicine at Mount Sinai
New York, NY, United States
EK

Eftichia V. Kontopoulos, MD

USFetus Research Consortium
Coral Gables, FL, United States
JZ

Jingwen Zhang, PhD

Natera, Inc.
Austin, TX, United States
ME

Melissa Egbert, MS

Natera, Inc.
Austin, TX, United States
SV

Sophia Vourthis, MPH

Natera, Inc.
Austin, TX, United States
Vivienne Souter, MD

Research Director, Obstetrical Care Outcomes Assessment Program
Foundation for Health Care Quality
Seattle, WA, United States
Clark T. Johnson, MD, MPH (he/him/his)

Division Director-Maternal Fetal Medicine Assistant Professor
Sinai Hospital of Baltimore
Baltimore, MD, United States

Objective: To evaluate outcomes in twin pregnancies stratified by zygosity based on SNP-based cell-free DNA screening (cfDNA).

Study Design: Prospective study of twin pregnancies undergoing SNP-based cfDNA following prenatal ultrasound (< 20 weeks’ gestation) at 13 US sites (Oct 2021-March 2023). Pregnancies with twin-to-twin transfusion syndrome (TTTS) prior to enrollment or a contraindication to cfDNA screening were excluded. cfDNA results, ultrasound findings, placental pathology, and maternal and newborn outcomes were collected. Dizygotic twins (DZ) on cfDNA were classified as dichorionic (DC). Monozygotic (MZ) twins on cfDNA were classified as monochorionic (MC) or DC based on placental pathology. Odds ratios (95% confidence intervals) were calculated to compare the pregnancy outcomes for MZ MC and MZ DC twins with those of DZ twins.

Results: 137 patients enrolled in the study. After exclusions for undetermined cfDNA (1), incomplete follow-up (11), and MZ twins with no placental pathology (2), 123 patients remained in the cohort: 76 DZ, 31 MZ MC, and 16 MZ DC. Placental pathology was available for 63/76 (82.9%) DZ twins and was DC in all. Median gestation at cfDNA was 12+5 weeks. Pregnancy outcomes by zygosity and chorionicity are shown in Table 1. TTTS occurred in 3.2%, selective intrauterine growth restriction (SIUGR) in 22.6%, and twin-anemia-polycythemia sequence (TAPS) in 9.7% of MC twins. MZ MC twins had the highest incidence of pregnancy complications including preterm birth and NICU admission. The incidence of small-for-gestational age (SGA) (birth weight < 10th percentile) was higher in the MZ DC group compared to the DZ group (OR=2.51; 95% CI 1.08,5.87).

Conclusion: SNP-based cfDNA in twin pregnancies can be used to determine the rate of complications by zygosity. This may help establish the actual rates of specific complications of MC twins, such as TTTS, SIUGR, and TAPS. The finding of a high incidence of SGA in MZ DC vs DZ DC twins may have important research and clinical implications, particularly on the frequency of growth surveillance.