This is the third in a three-part series about birth injuries in Los Angeles County.
Macrosomia is a condition in which a fetus’ birth weight is much greater than is normal during pregnancy. Generally, macrosomia is defined as a birth weight greater than 4000 grams or 8 pounds, 13 ounces. It is a condition that affects one in ten pregnancies.
Some factors that contribute to macrosomia – genetics, ethnicity, and the size of the parents – cannot be controlled. Other factors that may predispose a fetus to unusual growth in utero can be identified and should be addressed by the obstetrician. If the mother has gestational diabetes, excessive weight gain or diabetes mellitus, her fetus is at risk to develop macrosomia, which is associated with birth trauma to the baby and mother. Women whose pregnancies go on longer than they should are also at risk to develop macrosomic babies.
The larger the fetus, the greater likelihood that the baby and/or mother will suffer injuries during delivery. If there is ultrasound evidence that the baby is very large, the doctor needs to take this into consideration when discussing delivery options with the parents.
A woman with a history of having had several large babies without difficulty vaginally may be an appropriate candidate for a vaginal delivery. A petite woman pregnant with a first baby that appears on ultrasound to weigh nearly ten pounds, should be advised of the risks of vaginal delivery and advised to undergo a planned Cesarean section.
The greatest risk to the infant is getting stuck in the birth canal. This is called shoulder dystocia and puts the baby at risk of not getting sufficient oxygen, which can lead to brain damage and cerebral palsy. Another risk is that a doctor faced with a baby stuck in the birth canal will pull too hard on its head while trying to deliver it. This can cause injury to the network of nerves that supply the arm and shoulder, resulting in difficulty or inability to move the arm and hand on the affected side, which is usually the right side. This causes a condition called Erb’s palsy.
The potential injuries to the mother of vaginally delivering a too-large infant include tearing of the vagina and hemorrhaging (bleeding).
A doctor who does not adequately monitor a woman during her pregnancy to determine whether there is a likelihood that the baby may be too big to deliver vaginally or who does not take steps to address medical conditions that predispose a woman to having a macrosomic baby may be negligent. If he is, the consequences to mother and baby can have lifelong repercussions.