Obstetrics and Gynecology

Rhoda Sperling

• Publisher: Wiley-Blackwell
• Year: 2020
• Print ISBN: 9781119450115
• eBook ISBN: 9781119450078
• Edition: 1
• Topic: Medicine
• Subtopic: Gynecology, Obstetrics & Midwifery

Mount Sinai Expert Guides: Obstetrics and Gynecology provides specialty trainees and junior physicians with an extremely clinical, affordable and accessible handbook covering the key and hot topics in this complex field with focus throughout on clinical diagnosis and effective patient management.

Used as a point-of-care resource in the hospital and clinical setting, it present sthe very best in expert information in an attractive, quick and easy to navigate informative and well-structured manner, with features such as key points, potential pitfalls, management algorithms, and national/international guidelines on treatment.

PART 1
Obstetrics

CHAPTER 1
Multiple Gestations

Katherine A. Connolly¹ and Joanne L. Stone²

¹Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of California, San Francisco, CA

²Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Science, Icahn School of Medicine at Mount Sinai, New York, NY

Overall Bottom Line

• The incidence of twin gestation has risen due to advancing maternal age and the use of assisted reproductive techniques (ART).
• There are increased risks of a twin gestation, including preterm labor, preterm delivery, low birth weight, fetal growth restriction, gestational diabetes, preeclampsia, and need for cesarean delivery.
• Twin gestations require increased surveillance due to these increased risks.

Background

Definition of disease

• Twin gestation refers to an intrauterine gestation of two fetuses.

Disease classification

• Dizygotic twins occur after ovulation and fertilization of two different oocytes. This type of twins has two placentas and two amniotic sacs (Figure 1.1).
• Monozygotic twins result from ovulation and fertilization of one single oocyte, with subsequent division. Depending on what day the embryo splits, these monozygotic twins are further classified as the following:
  • Dichorionic/diamniotic (Day 1–3)
  • Monochorionic/diamniotic (Day 4–8) (Figure 1.2)
  • Monochorionic/monoamniotic (Day 8–13)
  • Conjoined twins (Day 13–15)

Incidence/prevalence

• The natural incidence of twins is 1/80.
• The incidence of multiple gestation increased by 76% from 1980 to 2009 due to ART and has since stabilized.
• Twins now account for 3% of live births.

Economic impact

• Twin gestations are associated with higher cost, which is mostly related to the increased rate of preterm delivery. The cost of a premature infant is up to 10 times greater than that of a term infant in the first year.

Predictive/risk factors

Risk factor	Contribution
Assisted reproductive technology	Accounts for 1/3 of all twin pregnancies
Maternal age	Fourfold increase from age 15 to age 35
Family history	Increased risk of dizygotic twins

Prevention

Bottom Line/Clinical Pearls

• The incidence of twin gestation has stabilized over time as the number of embryos transferred with ART has decreased. Single embryo transfer has become an increasingly common practice.

Screening

• Ultrasound in the first or early second trimester is essential in diagnosing twin gestation and establishing chorionicity (Figures 1.1 and 1.2).

Primary prevention

• Single embryo transfer to decrease the number of twin gestations that result from in vitro fertilization is an important prevention method. Splitting of an embryo into a monozygotic twin gestation, whether spontaneous or after ART, is not preventable.

Secondary prevention

• After a twin gestation is diagnosed, a multifetal pregnancy reduction procedure can be performed, resulting in a single fetus and improved pregnancy outcomes.
• Multifetal pregnancy reduction to a singleton gestation is associated with higher birth weights and lower rates of preterm deliveries.

Diagnosis

Bottom Line/Clinical Pearls

• The diagnosis of twins is made with ultrasound.
• This ultrasound should be done in the first or early second trimester in order to most accurately establish chorionicity, which has important implications for the pregnancy.

Typical presentation

• Twin gestation may be suspected if uterine size measures larger than would be expected for a given gestational age.
• Diagnosis can be confirmed only with ultrasound.

Clinical diagnosis

History

• Age
• Family history of twin gestation
• Use of ART

Physical examination

• Clinical examination of uterine size with bimanual exam and measurement of fundal height

Laboratory diagnosis

List of diagnostic tests

• The risk of aneuploidy is higher in dizygotic twins. The mathematical probability that a single fetus is affected is doub...

Table of contents

• Cover
• Title Page
• Copyright
• Contributors
• Series Foreword
• Preface
• About the Companion Website
• Part 1 Obstetrics
• Part 2 Gynecology
• Part 3 Reproductive Endocrinology
• Part 4 Gyn Oncology
• Part 5 Family Planning
• Index
• End User License Agreement