Epidemiologic Reports SurveysSeeing Double: A Nation of Twins From Sea to Shining SeaAdashi, Eli Y. MD, MSAuthor Information Warren Alpert Medical School, Brown University, Providence, RI Obstetric Anesthesia Digest: March 2017 - Volume 37 - Issue 1 - p 16 doi: 10.1097/01.aoa.0000512007.65720.37 Buy Metrics Abstract (Am J Obstet Gynecol. 2016;214(3):311–313) Twin birth rates in the United States have constantly been on the rise (33.9 per 1000 live births in 2014) as reported by the Division of Vital Statistics of the National Centers for Health Statistics. The adverse consequences of an increasing national twin birth rate include babies that are born “very preterm” (<32 completed weeks of gestation) or “preterm” (<37 completed weeks of gestation), and babies born with “very low birthweight” (<1500 g) or “low birthweight” (<2500 g). This commentary aimed to explain the ontogeny of the twin births “epidemic,” to describe the factors contributing to it, and to propose potential remedies for it. The basal/naturally occurring national twin birth rate was 20.1 per 1000 live births from 1949 to 1966. The first fertility-promoting drug (clomiphene citrate) was introduced in 1967 at which time the incidence of twin births gradually started to rise. The national twin birth rate grew steadily from 1986 as the in vitro fertilization (IVF) venture was just in progress. With the increasing utilization of IVF and the emergence of superovulation and subsequent intrauterine insemination (IUI), the national twin birth rate reached 25 per 1000 live births after a decade. The national twin birth rate had crossed the 30 per 1000 live births barrier by 2001 and had thereby resulted in an overall 1.7-fold increase compared with its baseline rate, with the rising trend yet to be reversed. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.