TY - CHAP M1 - Book, Section TI - Multifetal Pregnancy A1 - Cunningham, F. Gary A1 - Leveno, Kenneth J. A1 - Dashe, Jodi S. A1 - Hoffman, Barbara L. A1 - Spong, Catherine Y. A1 - Casey, Brian M. PY - 2022 T2 - Williams Obstetrics, 26e AB - Multifetal pregnancies may result from two or more fertilization events, from a single fertilization followed by a splitting of the zygote, or both. In part because of infertility therapy, the twin birth rate in the United States was 3.2 percent in 2019. For higher-order multifetal births, the number peaked in 1998 at 0.2 percent of all births. Subsequent efforts in the reproductive endocrinology community to curb this rate have led to declines. Specifically, the rate of triplets or more declined by 55 percent from 1998 to 2019 (Martin, 2021). SN - PB - McGraw Hill CY - New York, NY Y2 - 2024/12/11 UR - obgyn.mhmedical.com/content.aspx?aid=1190767311 ER -