Macrosomia Treatment & Management

Updated: Feb 03, 2017
  • Author: Anna R Baur, MD; Chief Editor: Christine Isaacs, MD  more...
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Treatment

Medical Care

Induction of labor for presumed fetal macrosomia has in recent history been discouraged due to unclear benefit. However, in a randomized controlled trial by Boulvain et al, 822 women with estimated fetal weight > 95th percentile at term were randomized to induction versus expectant management.  Induction of labor was associated with reduced risk of shoulder dystocia, however the study was underpowered to detect a difference in brachial plexus injury and none occurred in either group.  In addition, induction of labor did not increase cesarean section rate as people have feared. A Cochrane systematic review of four RCTs that included 1190 patients examined outcomes with induction of labor for large for gestational age. [41] The Boulvain RCT contributed 800 of the 1190 patients and dominated the findings of the review.  The review concluded that induction of labor in suspected fetal macrosomia does not reduce the risk of brachial plexus injury but does reduce birth weight, as well as risk of skeletal injury and shoulder dystocia. [42]

Macrosomia is related to perinatal complications and the term fetus increases its body mass approximately 150-200g per week.  Early term or 39-week induction of labor can reduce rates of macrosomia compared with expectant management, and therefore may decrease the complications of macrosomia. Nevertheless, ACOG continues to recommend against induction of labor for suspected large for gestational age infants at any gestational age.

American College of Obstetricians and Gynecologists Practice Bulletin 173 (titled Fetal Macrosomia) states that cesarean section can be offered to mothers with suspected fetal weights >5000g if the mother does not have glucose intolerance and >4500g if the mother does have glucose intolerance. [1]

Cesarean delivery to reduce the risk associated with macrosomia may place the mother at risk, and subsequent pregnancies are at risk of uterine dehiscence before or during the onset of labor. Not all cases of nerve injuries can be prevented by cesarean delivery because some occur in utero. Estimates indicate that as many as 3,695 cesarean deliveries in non-diabetic women and 443 cesarean deliveries in diabetic women must be performed to prevent a single permanent brachial plexus nerve injury in infants of estimated fetal weight greater than 4,500 g. [43]

Decision making regarding delivery should be individualized to the patient, taking into account risks and benefits of both macrosomia and other delivery factors such as surgical risks, including implications for future childbearing, and the neonatal risks of early term delivery.

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Surgical Care

The obstetrician involved in the care of a macrosomic infant must be familiar with procedures that release a shoulder dystocia at delivery.

Because macrosomic infants are at increased risk of cesarean delivery the provider must be capable of performing a cesarean delivery or must have backup help available in case cesarean delivery is necessary.

Operative vaginal deliveries (eg, forceps, vacuum) must be performed with caution in infants with risk factors for macrosomia. Midpelvic procedures are associated with a much greater risk of significant shoulder dystocia (50%) in macrosomic infants than non macrosomic infants. [44]

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Consultations

In patients with poorly controlled diabetes resulting in macrosomia, consultation with a maternal fetal medicine specialist to obtain better control may be useful.

In cases of significant macrosomia (estimated fetal weight >99th percentile), a careful evaluation of the dates and a sonographic evaluation of fetal anatomy can be helpful to investigate potential causes of the macrosomia. Incorrect gestational age is frequently encountered and may result in estimated fetal weights that are greater than the 90th percentile but usually should not result in estimations greater than 4000 or 4500 grams. Intra-abdominal and intracranial masses may result in larger abdomen and head measurements resulting in a large estimated fetal weight. Such causes should be diagnosed prior to delivery if at all possible.

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Diet

Pre-gestational obesity and excessive gestational weight gain in pregnancy are two of the strongest predictors of macrosomia at birth; therefore, a possible intervention to prevent macrosomia may be nutrition education and an exercise program. Intuitively, this type of intervention, if successful, may reduce the risks of macrosomia in those women who are obese prior to pregnancy or who may gain excessive weight in pregnancy. In diabetic patients, maternal diet alone, without the use of insulin, did not alter rates of macrosomia. [45, 46]

Excessive maternal weight gain can double the risk of macrosomia; thus, a reasonable suggestion is careful weight control for women who exceed the recommended weight gain in pregnancy. [47, 48, 49]

A multi-center RCT by Landon et al assessed 958 women with mild gestational diabetes and randomized them to usual prenatal care vs diet and lifestyle intervention with treatment as medically indicated for glycemic control. The study found a statistically significant difference in the control group vs treatment group in the frequency of large-for-gestational-age infants, 14.5% vs 7.1%, as well as reduced frequency of shoulder dystocia (4.0% vs 1.5%) and birth weight over 4000 g (14.3% v 5.9%). [30]

Dietary and weight gain guideline education should be provided for obese patients of patients experiencing excessive gestational weight gain as these are associated with macrosomia, gestational diabetes, cesarean delivery, and preeclampsia.  Such intervention may potentially reduce maternal and neonatal risks. At the present time, clinical trials are lacking support of the effectiveness of such intervention. [50]

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