Macrosomia and Birth Injury

When babies are large for their gestational age (macrosomic), this classifies the pregnancies as high-risk. Fetal macrosomia can occur due to maternal obesity or gestational diabetes, along with several other untreated maternal health conditions. The key to preventing macrosomia is proper health screening of the mother. Physicians should closely monitor maternal health. It is imperative that macrosomia is diagnosed prenatally so that the timing and management of delivery can be planned. Measurement tools such as ultrasounds, fundal height, amniotic fluid levels, and Leopold maneuvers should be used to determine whether the baby will be of an excessively large size. The most accurate tests for estimating fetal weight (ultrasound) should be used. Medical professionals who fail to do this are deviating from the standards of careand this can pose health risks to the mother and child.

Macrosomia, also known as large for gestational age (LGA), is a condition in which a fetus or newborn weighs more than 4000 grams, although the risk increases greatly at 4500 grams. The American College of Obstetricians and Gynecologists (ACOG) supports the use of the 4500-gram threshold but acknowledges there is a risk of morbidity at 4000 grams.  These larger than average babies create a high-risk pregnancy situation.  Vaginal delivery is very difficult when a baby is macrosomic.  Macrosomia places the baby at risk of having birth injuries such as cerebral palsy, Erb’s palsy, hypoxic-ischemic encephalopathy (HIE), brain bleeds, and other traumatic injuries.  Due to the increased risk of birth injuries when a baby is macrosomic, the pregnancy, labor, and delivery must be very closely monitored and managed.  Often, a C-section delivery is the safest way to deliver a macrosomic baby.

Macrosomia - Large Infant Size

Causes of Fetal Macrosomia

Fetal macrosomia usually develops when a baby receives too many nutrients.  This can occur when the mother is obese or has diabetes, particularly gestational diabetes.  In some instances, a baby has a medical condition that speeds fetal growth. 

Risk Factors for Fetal Macrosomia

There are many factors that increase the risk of macrosomia.  When any of these risks are present, the physician should closely monitor the mother and baby for macrosomia and its potential complications.  Risk factors for macrosomia include the following:

  • Maternal diabetes: Both gestational diabetes and diabetes mellitus (DM, or type 2 diabetes) can cause the baby to grow very large.  This is because diabetes increases the mother’s blood sugar and insulin levels, which both stimulate fetal growth.
  • Maternal obesity: If a mother is obese or gains excessive weight during pregnancy, macrosomia is more likely.
  • Prior delivery of a macrosomic baby
  • Previous pregnancies: The risk of fetal macrosomia increases with each pregnancy.  Up to the fifth pregnancy, the average birth weight for each successive pregnancy typically increases by up to 4 ounces (120 grams).
  • Post-term pregnancy: Pregnancies that go beyond 40 weeks have an increased incidence of macrosomia.
  • Multiple gestations: Being pregnant with twins, triplets, etc. increases the risk of macrosomia.
  • Advanced maternal age: Women older than 35 years are more likely to have a baby diagnosed with macrosomia.
  • A male baby: Male fetuses and infants tend to weigh more than females.  Most babies who weigh more than 4500 grams are male.
  • Genetic factors: Taller, heavier parents tend to have larger babies.
  • Use of antibiotics during pregnancy: Antibiotics such as amoxicillin and pivampicillin put the baby at risk for macrosomia.
  • Congenital anomalies: An anomaly such as transposition of the great vessels (a cardiac malformation) can increase the chances of macrosomia.
  • Genetic disorders of overgrowth: Disorders such as Sotos syndrome, which is characterized by excessive growth during the first 2-3 years of life, increase the risk of macrosomia.

Macrosomia is more likely to be a result of maternal diabetes, obesity or weight gain than any other causes.  In addition, maternal diabetes and macrosomia are the strongest risk factors for shoulder dystocia (a situation in which when the baby’s shoulder gets stuck in the mother’s pelvis during delivery), and the highest risk of shoulder dystocia occurs when both these factors are present.

Signs of Fetal Macrosomia

Signs and symptoms of macrosomia include the following:Fetal Macrosomia and Birth Injury

  • Large fundal height: During prenatal visits, the physician should monitor the mother’s fundal height.  This is the distance from the top of the uterus to the pubic bone.  A fundal height that measures larger than expected could be a sign of macrosomia.
  • Excessive amniotic fluid (polyhydramnios): Too much amniotic fluid – the fluid that surrounds and protects the baby during pregnancy – may be a sign that the baby is larger than average.  The amount of fluid reflects the baby’s urine output, and a larger baby produces more urine.  Some conditions that increase a babies size can also increase the baby’s urine output.

Diagnosing Fetal Macrosomia

  • Ultrasound: If the baby is large enough, an ultrasound can be used to determine the baby’s size, although these scans can be up to 15% inaccurate.  In the third trimester, the physician will take measurements of parts of the baby’s body, such as the head, abdomen, and femur, and will then enter these measurements into a formula to estimate the baby’s weight.  The medical team must be certain the date of conception is accurate to ensure accurate calculations of the baby’s size.
  • Abdominal circumference (AC) is the most common and reliable single parameter used to assess the risk of macrosomia.  Assessment of an enlarged AC on ultrasound should prompt a reevaluation of fetal growth in three to four weeks, especially in women with diabetes.  Predictions for absence or presence of macrosomia can generally be made after two successive scans.
  • Leopold maneuver: Fetal weight can be estimated by the physician with simple palpation (pushing) on the mother’s abdomen.
  • Measurement of fundal height

If macrosomia is suspected, the medical team should use nonstress testing to monitor the baby’s well-being.  A nonstress test measures the baby’s heart rate in response to his or her own movements.  If the baby’s excess growth is thought to be the result of a maternal condition, the physician should recommend two nonstress tests each week – starting as early as week 32 of pregnancy.

Managing Fetal Macrosomia

The underlying cause of macrosomia frequently must be managed, particularly in cases of diabetes.  Obese women should be instructed to gain less weight and may require a referral to a dietician or nutritionist.

If the physician suspects macrosomia, a vaginal delivery still may be attempted, but only after the patient is informed of the risks.  Macrosomia increases the likelihood that instruments such as forceps and vacuum extractors will be used to assist in the delivery.  Instrument delivery is a risk factor associated with permanent brachial plexus injury and other birth injuries.  Thus, risk factors for shoulder dystocia should be carefully reviewed prior to utilization of forceps and vacuum extractors.  Physicians should try and avoid the procedure if substantial risk appears to be present.

If the pregnancy is allowed to run its course, or if induction is attempted, the physician should be prepared to deal with a shoulder dystocia situation and should be prepared to deliver by C-section in the event of an emergency.

Routine induction of labor with drugs such as Pitocin/oxytocin is not recommended.   Research shows that labor induction does not reduce the risk of complications associated with macrosomia, and might increase the need for a C-section.  Furthermore, labor induction prior to term is associated with increased neonatal morbidity.

If a C-section is recommended before week 39 of pregnancy, the physician will test a sample of amniotic fluid to determine whether the baby’s lungs are mature enough for birth.  A planned C-section is recommended for women whose previous pregnancy was complicated by shoulder dystocia, particularly when a brachial plexus injury occurred.

If the mother has diabetes and it has been determined that the baby weighs more than 4500 grams, a C-section may be the safest way to deliver the baby.  A C-section will also likely be recommended if the baby weighs 5000 grams or more and the mother has no history of gestational diabetes.

After the baby is born, he or she will likely be examined for signs of birth injuries, abnormally low blood sugar (hypoglycemia), and a blood disorder that affects the red blood cell count (polycythemia).

Fetal Complications and Birth Injuries Associated with Macrosomia

  • Injuries from forceps and vacuum extractors: Inappropriate use of these instruments can cause injuries due to the multiple forces being exerted on the baby.  Intracranial hemorrhages (brain bleeds), blood clots leading to strokes, brain swelling and damage leading to seizures and ischemia, brachial plexus injuries, and cerebral palsy all can result from improper use of forceps and vacuum extractors.
  • Brachial plexus injuries: Erb’s palsy occurs when the brachial plexus nerve in the upper arm and neck becomes torn due to the downward traction that is applied to the baby’s head and neck when the baby gets stuck in the birth canal.  This usually happens due to shoulder dystocia, which occurs when the baby’s shoulders have difficulty passing below the mother’s pubic bone.  In other words, the shoulder gets stuck on the bone while the physicians are pulling the baby out.  Shoulder dystocia is considered an obstetrical emergency due to the potential for the umbilical cord to become compressed within the birth canal, depriving the baby of oxygen, which can lead to permanent injuries such as HIE.
  • C-section: Macrosomia increases the probability of the need for C-section and emergency C-section.  If a baby becomes lodged in the birth canal, time is critical and a delay can cause permanent brain damage, especially if the umbilical cord is prolapsed.  The physician must be very skilled in this procedure in order to minimize the time of the procedure and damage caused oxygen deprivation.
  • HIE: This is a condition whereby a baby is severely deprived of oxygen, resulting in cell death and, often, permanent injuries such as cerebral palsy, seizures, and learning disabilities.  This happens many times when the baby is too big to fit through the birth canal and gets stuck.
  • Uterine rupture: If a mother had a prior C-section or major uterine surgery, macrosomia increases the risk of uterine rupture, which is a serious complication in which the uterus tears open along the scar line from the C-section or other surgery.  This can cause the baby to spill into the mother’s abdomen, which can cause maternal or fetal death, or fetal asphyxia (HIE).  An emergency C-section is required to prevent or minimize these serious complications.

Macrosomia, Birth Injuries, and Medical Malpractice

When risk factors for macrosomia are present, it is essential that the physicians monitor the mother and baby very closely and be prepared for a potential delivery by C-section.  In certain situations, it may be necessary to plan to deliver the baby early.  There are many issues physicians must examine when facing macrosomia.  It is crucial that the physician and medical team be very skilled in handling all issues pertaining to the pregnancy and delivery.  It is negligence when a mother and baby are not properly assessed and monitored.  Failure to act skillfully and, if necessary, quickly, also constitutes negligence.  If this negligence leads to injury of the mother or baby, it is medical malpractice.

Listed below are issues that may constitute negligence:

  • Obstetrical instruments (forceps or vacuum extractors) were inappropriately placed or misused.
  • There was a failure to order a C-section.
  • The physician caused a birth injury by forcing a vaginal birth.
  • A physician failed to act promptly during an emergency, which may include the failure to quickly order and perform a C-section.
  • Pitocin/oxytocin was used improperly.
  • The physician failed to give the patient adequate information on the risks and alternatives of a certain course of action, and/or did not get informed consent.

Reiter & Walsh, P.C. | Award-Winning Birth Trauma Attorneys Handling Macrosomia Cases Since 1997

At Reiter & Walsh ABC Law Centers, we focus solely on birth injury cases. We understand the complex legal issues involved with macrosomia cases and will help you to obtain the compensation to which you are entitled. While we’re based in Michigan, we help clients all over the country, in states including Michigan, Ohio, Pennsylvania, Texas, Tennessee, Wisconsin, Arkansas, Mississippi, Washington D.C., and more. To begin your free birth trauma case review, please contact us in any of the following ways:

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Video: Abnormal Labor

Macrosomia can cause abnormal or stalled labor during delivery. Learn more here.

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