Macrosomia: Determination of EFW and Recommendations for Delivery
Learning Objectives and CME/Disclosure Information
This activity is intended for healthcare providers delivering care to women and their families.
After completing this activity, the participant should be better able to:
1. Define macrosomia 2. Discuss the role of prophylactic cesarean section with women where there is suspected fetal macrosomia
Estimated time to complete activity: 0.25 hours
Susan J. Gross, MD, FRCSC, FACOG, FACMG President and CEO, The ObG Project
Disclosure of Conflicts of Interest
Postgraduate Institute for Medicine (PIM) requires faculty, planners, and others in control of educational content to disclose all their financial relationships with ineligible companies. All identified conflicts of interest (COI) are thoroughly vetted and mitigated according to PIM policy. PIM is committed to providing its learners with high quality accredited continuing education activities and related materials that promote improvements or quality in healthcare and not a specific proprietary business interest of an ineligible company.
The PIM planners and others have nothing to disclose. The OBG Project planners and others have nothing to disclose.
Faculty: Susan J. Gross, MD, receives consulting fees from Cradle Genomics, and has financial interest in The ObG Project, Inc.
Planners and Managers: The PIM planners and managers, Trace Hutchison, PharmD, Samantha Mattiucci, PharmD, CHCP, Judi Smelker-Mitchek, MBA, MSN, RN, and Jan Schultz, MSN, RN, CHCP have nothing to disclose.
Method of Participation and Request for Credit
Fees for participating and receiving CME credit for this activity are as posted on The ObG Project website. During the period from Dec 31 2017 through Dec 31 2018, participants must read the learning objectives and faculty disclosures and study the educational activity.
If you wish to receive acknowledgment for completing this activity, please complete the post-test and evaluation. Upon registering and successfully completing the post-test with a score of 100% and the activity evaluation, your certificate will be made available immediately.
For Pharmacists: Upon successfully completing the post-test with a score of 100% and the activity evaluation form, transcript information will be sent to the NABP CPE Monitor Service within 4 weeks.
Joint Accreditation Statement
In support of improving patient care, this activity has been planned and implemented by the Postgraduate Institute for Medicine and The ObG Project. Postgraduate Institute for Medicine is jointly accredited by the Accreditation Council for Continuing Medical Education (ACCME), the Accreditation Council for Pharmacy Education (ACPE), and the American Nurses Credentialing Center (ANCC), to provide continuing education for the healthcare team.
Physician Continuing Medical Education
Postgraduate Institute for Medicine designates this enduring material for a maximum of 0.25 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.
Continuing Nursing Education
The maximum number of hours awarded for this Continuing Nursing Education activity is 0.2 contact hours.
The term fetal macrosomia implies growth beyond an absolute birth weight of 4000 grams or 4500 grams, regardless of gestational age. The risk of morbidity for both infants and mothers increases when the birthweight is between 4000 and 4500 grams. Risks for maternal and newborn morbidity rise considerably with birthweights >4500g. A correct diagnosis can only be made after weighing an infant at birth, as ultrasound prediction is not precise.
Consider a prophylactic cesarean for suspected fetal macrosomia if the EFW (estimated fetal weight) is > 5000 grams in women without diabetes
Consider a prophylactic cesarean for suspected fetal macrosomia if the EFW is > 4500 grams in women with diabetes
Induction before 39w0d is not suggested for suspected fetal macrosomia as induction has not been shown to improve maternal or fetal outcomes
Suspected fetal macrosomia is not a contraindication to a trial of labor after cesarean
In the United States, 7.8% of all live-born infants weigh > 4000 grams and 1% weigh > 4500 grams. The most serious complication of fetal macrosomia is shoulder dystocia which complicates 0.2-3.0% of all vaginal deliveries. When the birthweight is > 4500 grams, the shoulder dystocia rate increases to 9-14%. The shoulder dystocia rate increases to 20-50% in the presence of maternal diabetes when the birthweight is > 4500 grams. ‘Large for gestational age (LGA)’ also refers to excessive fetal growth, but rather than absolute weight, LGA is usually defined as ≥90th percentile for a given gestational age.
Risk Factors for Macrosomia
Preexisting maternal diabetes
Uncontrolled gestational diabetes
Excessive gestational weight gain
Excessive inter pregnancy weight gain
Prior macrosomic infant
Maternal nonsmoking status
Maternal Risks Associated with Macrosomia
Increased risk of cesarean delivery
Fetal Risks Associated with Macrosomia
Shoulder dystocia leading to brachial plexus injury or clavicular fracture
Decreased 5 minute Apgar score
Increased rates of admission to the NICU, including longer stays
Obesity later in life
Accuracy of EFW Measurement
“Poor predictor of macrosomia”: Better at ruling out than identifying macrosomia
Sensitivity: 29% to 70%
Abdominal palpation maneuvers
Sensitivity: 16% to 68%
Specificity: 90% to 99%
PPV: 38% to 80%
In women with diabetes
“Clinical estimates of macrosomia are as predictive as those derived with ultrasonography”
Prediction of birth weight >4,500g
Sensitivity: 10% to 45%
Specificity: 57% to 99%
PPV: 11% to 44%
NPV: 92% to 99%
Prediction of birth weight >4,000g
Newborns>4,500 g: Mean absolute percent error of 13% | Increases with greater EFW
Nonmacrosomic newborns: Mean absolute percent error of 8%
Note: Upon review of current literature, ACOG states
No single formula based on ultrasound biometry performs significantly better than others for the detection of macrosomia more than 4,500 g
Similar to clinical estimates of fetal weight, ultrasonography can be used most effectively as a tool to rule out macrosomia, which may help avoid maternal and fetal morbidity
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Disclosure of Unlabeled Use
This educational activity may contain discussion of published and/or investigational uses of agents that are not indicated by the FDA. The planners of this activity do not recommend the use of any agent outside of the labeled indications.
The opinions expressed in the educational activity are those of the faculty and do not necessarily represent the views of the planners. Please refer to the official prescribing information for each product for discussion of approved indications, contraindications, and warnings.
Participants have an implied responsibility to use the newly acquired information to enhance patient outcomes and their own professional development. The information
presented in this activity is not meant to serve as a guideline for patient management. Any procedures, medications, or other courses of diagnosis or treatment discussed or suggested in this activity should not be used by clinicians without evaluation of their patient’s conditions and possible contraindications and/or dangers in use, review of any applicable manufacturer’s product information, and comparison with recommendations of other authorities.
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