Society for Maternal‐Fetal Medicine Special Statement: Updated checklists for management of monochorionic twin pregnancy

Abstract

Approximately 20% of twin pregnancies are monochorionic—either monochorionic/diamniotic (MC/DA) or monochorionic/monoamniotic (MC/MA). The management of monochorionic twin pregnancy involves several additional interventions beyond the routine management of singletons or dichorionic twins. In 2020, the Society for Maternal‐Fetal Medicine (SMFM) published checklists for the management of MC/DA and MC/MA twin pregnancies. SMFM now presents updated versions of these checklists reflecting recent changes in practice recommendations. Suggestions for implementing the use of the checklists into practice are also included. This Statement replaces the 2020 SMFM Special Statement: Updated checklists for management of monochorionic twin pregnancy.

1. INTRODUCTION

The incidence of twin births in the United States nearly doubled between 1980 and 2009, from 18.9 to 33.3 per 1000 births [1]. Most of the increased incidence was attributable to the increased use of assisted reproductive technology and a shift toward older maternal age [1]. The incidence has since demonstrated a slight downward trend, from 34.5 per 1000 births in 2010 to 30.7 per 1000 births in 2023 [2]. Twin gestation, regardless of chorionicity, is associated with increased rates of maternal and perinatal complications compared with singleton gestation, including congenital abnormalities, preterm birth, hypertensive disorders, gestational diabetes, fetal growth restriction, stillbirth [3, 4], and neonatal death [5, 6].

Approximately 20% of twin pregnancies are monochorionic—either monochorionic/diamniotic (MC/DA) or monochorionic/monoamniotic (MC/MA). Compared with dichorionic twins, monochorionic twins are at even greater increased risk of stillbirth [3], congenital fetal anomalies, preterm birth, and fetal growth restriction [5, 6]. In addition, monochorionicity carries unique risks owing to vascular anastomoses within the monochorionic placenta that can lead to complications such as twin‐twin transfusion syndrome (TTTS), twin anemia‐polycythemia sequence (TAPS), and twin reversed arterial perfusion sequence. These complications occur in approximately 15% of monochorionic twin pregnancies [5, 6]. Monoamniotic twinning, which occurs in approximately 3% of monochorionic twin pregnancies (0.02% of all pregnancies), carries a high risk of stillbirth owing to umbilical cord entanglement [7, 8].

With appropriate management, some of the complications of monochorionic twin pregnancy can be prevented (e.g., low‐dose aspirin prophylaxis to decrease the risk of preeclampsia, early delivery to decrease the risk of stillbirth) or treated (e.g., photocoagulation of intraplacental vascular anastomoses in TTTS). Other complications can be mitigated with early diagnosis (e.g., ultrasound examinations to detect congenital anomalies or growth discordance). Thus, the management of monochorionic twin pregnancy involves several additional interventions beyond the routine management of singletons or dichorionic twins. These interventions include early‐pregnancy counseling about potential complications; a detailed sonographic fetal anatomy survey and fetal echocardiography; serial sonographic surveillance to detect signs of twin–twin transfusion, hydrops, or growth discordance; antepartum fetal surveillance; and antenatal corticosteroids in preparation for planned early delivery [6].

Because of the number and complexity of extra management steps recommended for monochorionic twin pregnancy and because these steps are taken at various time points throughout pregnancy, the use of a cognitive aid such as a checklist can help reduce errors of omission [9]. In 2020, the Society for Maternal‐Fetal Medicine (SMFM) published two checklists for monochorionic twin pregnancy, one for MC/DA twins and the other for MC/MA twins [10]. These checklists were based largely on guidance on multifetal gestations authored jointly by the American College of Obstetricians and Gynecologists (ACOG) and SMFM [5].

Here, SMFM presents updated versions of these two checklists that reflect recent changes in practice recommendations. Suggestions for implementing the use of the checklists into antenatal care practices are also included.

2. CHECKLISTS FOR THE MANAGEMENT OF MONOCHORIONIC TWIN GESTATIONS

The updated checklists for MC/DA and MC/MA twin gestations are shown in Figures 1 and 2, respectively. The content is based on ACOG/SMFM Practice Bulletin number 231 on multifetal gestations [6], the American Institute of Ultrasound in Medicine practice parameter on first‐trimester detailed ultrasound examination [11], SMFM Consult number 72 on TTTS and TAPS [12], ACOG/SMFM Committee Opinion number 828 on antepartum fetal surveillance [13], and ACOG/SMFM Committee Opinion number 831 on medically indicated late‐preterm and early‐term deliveries [14].

FIGURE 1.

Sample checklist for management of monochorionic/diamniotic twin pregnancy.

FIGURE 2.

Sample checklist for management of monochorionic/monoamniotic twin pregnancy.

The checklists have several content updates since the 2020 versions:

1. Addition of first‐trimester detailed fetal anatomy ultrasonography in light of increased risk of congenital anomalies [11].

2. Under “Counseling,” deletion of item regarding selective termination of one twin.

3. Addition of consideration of umbilical and middle cerebral artery (MCA) Doppler studies to routine surveillance. SMFM Consult 72 recommends that MCA Doppler studies to screen for TAPS should be considered with routine monochorionic twin surveillance ultrasonography beginning at 16–20 weeks of gestation [12]. Additional factors, such as local resources and patient access to care, should be considered when determining whether to include umbilical artery and MCA Doppler studies in routine monochorionic twin surveillance strategies.

4. In uncomplicated twin gestations, assessment of twin growth should occur every 4 weeks [6]. The 2020 version indicated every 2–4 weeks.

5. Initiation of weekly antepartum fetal surveillance (biophysical profile and nonstress test) is recommended at 32 0/7 weeks of gestation for uncomplicated MC/DA pregnancy and individualized in consultation with a maternal‐fetal medicine specialist for MC/MA or complicated MC/DA pregnancy [6, 13]. The 2020 version did not specify start time or frequency.

6. Delivery at 34 0/7 to 37 6/7 weeks of gestation recommended for MC/DA twins [14]. The 2020 version stated only “by 37 6/7 weeks of gestation.”

7. In uncomplicated MC/DA twins with vertex presentation of the presenting twin, regardless of the presentation of the second twin, vaginal birth may be considered at 32 weeks of gestation or later, provided that an obstetrician with experience in managing a nonvertex presenting second twin is available and the patient is engaged in shared decision‐making [6].

The checklist design adheres to the guidance from ACOG's Checklist for Checklists [15]. Each checklist uses a sans‐serif font; avoids the use of color; includes a version date; has a simple, uncluttered format; and fits on one page.

3. SUGGESTIONS FOR IMPLEMENTATION

The checklists are intended to guide the antepartum care of monochorionic twin pregnancy. Thus, they are primarily intended to be used in the prenatal care clinic and not the hospital. Their purpose is to reduce the probability that prenatal care professionals will omit one of the special tasks indicated for the management of these complex pregnancies.

Each prenatal care practice should decide whether they want to use the checklists or whether they expect their staff to rely on training and memory to perform all the tasks listed. Lapses in care may be less likely if the checklists are used. If the practice decides to use checklists, the practice members should reach consensus regarding several items that are discretionary, including the following:

1. Inclusion of routine umbilical artery and MCA Doppler measurements during serial ultrasound examinations. SMFM notes that this decision should be guided by available local resources and patient access to care [12].

2. Routine hospitalization of patients with MC/MA twin pregnancy for intensified surveillance, and, if so, at what gestational age and using what type and frequency of monitoring. Inpatient monitoring may decrease the risk of stillbirth compared with outpatient monitoring [7, 8], but ACOG and SMFM note that the optimal management of MC/MA twin pregnancy remains uncertain [6]. If practice members agree on outpatient monitoring, they should reach a consensus regarding the type and frequency of monitoring to be used and the indications for hospitalization.

3. Specification of different “deliver by” gestational ages than the ones we have listed based on ACOG/SMFM guidelines. Some evidence suggests that earlier delivery may reduce the overall risk of perinatal death [16].

4. Any other management issues in which variation within the practice exists. If the practice members reach a consensus on these issues, they should modify the checklists to fit their practice.

An important point for each practice to consider is whether to have the checklist exist as a digital form in the patient's electronic health record, a paper form in a physical chart, or simply a task list for practice members to reference without specifically including the form in the patient's record. If a practice wants to use digital forms, then resources will be needed to develop a special module within the electronic charting system. Paper chart forms may be relatively easier to implement, but they raise additional questions. For example, does each entry need a practice member's signature, date, and time? Where will the paper form be kept if the practice primarily uses electronic charting? If a practice decides to simply use the checklist as a reference and not include it in the patient chart, will a copy of the checklists be stored where members can quickly reference it, such as a practice protocol binder or a digital reference file on each member's computer? If a paper version is used, measures should be taken to ensure that it remains with the medical record if a patient transfers to a different practice or health care system.

Checklists should evolve as new knowledge is gained and practice patterns change. After implementation, practice members should pay attention to any checklist items that might need to be added, revised, or corrected. If revisions are made, the version date should be edited, and copies of older versions should be discarded.

4. POSSIBLE QUALITY INDICATORS

We suggest the following quality indicators to assess the effectiveness of utilization of the checklist:

1. Percentage of patients who received detailed first‐trimester ultrasound examination to screen for congenital anomalies [11]

2. Percentage of patients who started low‐dose aspirin by 16 weeks of gestation [17]

3. Percentage of patients who had fetal echocardiography by 22 weeks of gestation [18]

4. Percentage of patients who delivered by the suggested gestational age [14]

5. Percentage of patients with perinatal survival of two, one, or no twins

To address racial and ethnic disparities in perinatal outcomes, each of these indicators should be stratified by race and ethnicity.

The use of this information is voluntary, and clinicians should be familiar with and comply with all applicable laws and regulations.

All authors and committee members have filed a disclosure of interests delineating personal, professional, business, or other relevant financial or nonfinancial interests in relation to this publication. Any substantial conflicts of interest have been addressed through a process approved by the Society for Maternal‐Fetal Medicine (SMFM) Board of Directors. SMFM has neither solicited nor accepted any commercial involvement in the specific content development of this publication.

This document has undergone an internal peer review through a multilevel committee process within SMFM. This review involves critique and feedback from the SMFM Patient Safety and Quality Committee and Document Review Committee and final approval by the SMFM Executive Committee. SMFM accepts sole responsibility for the document content. SMFM publications do not undergo editorial and peer review by Pregnancy. The SMFM Patient Safety and Quality Committee reviews publications every 24 to 36 months and issues updates as needed. Further details regarding SMFM publications can be found at www.smfm.org/publications.

SMFM recognizes that obstetrical patients have diverse gender identities and strives to use gender‐inclusive language in all publications. SMFM uses terms such as “pregnant person” and “pregnant individual” and the singular pronoun “they.” When describing study populations used in research, SMFM uses the terminology reported by the study investigators.

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