#216 Macrosomia Flashcards
What is the definition of large for gestational age?
Implies a birth weight equal to or more than the 90th percentile for a given gestational age
What is the definition of macrosomia?
Implies growth beyond an absolute birth weight, historically 4,000 g or 4,500 g, regardless of the gestational age
True or false: Increasing birth weight increases the likelihood of labor abnormalities, shoulder dystocia, birth trauma, and permanent injury to the newborn increases.
True
What % of all live-born newborns in the US weigh more than 4,000g? What % more than 4,500g? What % more than 5,000g?
7.8%; 1%; 0.1%
Rate of LGA in normal weight women vs obese women (without GDM)? Rate of LGA in normal weight women vs obese women with GDM?
- 7% in normal BMI women w/o GDM
- 7% in obese women w/o GDM
- 6% in normal BMI women w/ GDM
- 3% in obese women w/ GDM
What maternal factors predispose a newborn to macrosomia?
constitutional factors, preexisting diabetes and GDM, maternal prepregnancy obesity, excessive gestational weight gain, abnormal fasting and postprandial glucose levels, dyslipidemia, prior macrosomic newborn, postterm pregnancy
Maternal hyperglycemia can lead to fetal macrosomia via the release of what in the fetus?
insulin, insulin-like growth factors, and growth hormone
Is an elevated fasting blood glucose or elevated postprandial more strongly associated with fetal macrosomia?
Fasting
Is the risk of macrosomia increased in women with GDM even with treatment?
Yes
By how much does GDM increase the risk of macrosomia?
2-3 fold
What is the rate of LGA in women with GDMA1, GDMA2, and preexisting diabetes?
29% - GDMA1
30% - GDMA2
38% - preexisting diabetes
Does the type of macrosomia related to maternal hyperglycemia differ compared to macrosomia related to other risk factors (postterm, prev macrosomic child)? If so, how?
Yes. More total body fat, larger shoulder and upper-extremity circumferences, higher upper-extremity skin-fold measurements, and smaller head-to-abdominal-circumference ratios
Do newborns of women with diabetes have increased risk of shoulder dystocia, clavicular fracture, or brachial plexus palsy regardless of weight, compared to women without DM?
Yes
What is the single strongest individual risk factor for macrosomia?
History of macrosomia
Does maternal birth weight have an impact on risk of macrosomia in offspring?
Yes, women who exceeded 3600g at birth are twice as likely to give birth to baby weight >4000g than someone who was born at 2700-3500g.
Do multiparity and/or grand multiparity increase the risk of macrosomia?
Both increase the risk
How can you make an accurate diagnosis of macrosomia?
Weight the child after birth
Does ultrasound prediction of fetal weight improve or worsen with increasing fetal weight?
Worsens
What is the sensitivity of ultrasound for predicting fetal weight > 4000g? Specificity?
56% sensitivity. 96% specificity
Does individual growth-curve modeling improve the prediction of macrosomia?
No
Do longitudinal ultrasound examinations improve the prediction of macrosomia?
no
Does MRI or ultrasound have better sensitivity to detect macrosomia? Specificity?
MRI has better sensitivity and specificity at detection of macrosomia
How does physical exam compare to ultrasound to estimate fetal weight?
No studies have shown that ultrasonography is superior to physical examination in a clinically meaningful way
How does a parous woman’s prediction of fetal weight compare to ultrasound exam and physical exam estimates?
Predict just as well
What is the primary maternal risk associated with macrosomia?
Increased risk of cesarean birth
How does the rate of cesarean section for women with a baby >4500g compare to women with smaller babies
Risk for cesarean section is at least 2x
Is labor protraction more common with macrosomia?
Yes
Are arrest disorders more common with macrosomia?
Yes
Does a predelivery prediction of macrosomia (despite actual birth weight) affect the rate of diagnosis of labor abnormalities and cesarean birth?
Yes!
Does macrosomia increase the risk of postpartum hemorrhage?
Yes
Does macrosomia increase the risk of chorioamnionitis?
yes
Does macrosomia increase the risk of significant vaginal lacerations?
Yes
Shoulder dystocia occurs in what % of all vaginal deliveries?
0.2-3%
What is the risk of shoulder dystocia when birth weight is >4500g in all comers? In those with diabetes?
All comers: 9-14%
Diabetics: 20-50%
Injury to what nerve roots of the brachial plexus lead to Erb-Duchenne paralysis?
C5 and C6
Injury to nerve roots C5 and C6 of the brachial plexus cause what sort of paralysis?
Erb-Duchenne paralysis
Fracture of the clavicle complications what % of all births? How does macrosomia affect this risk (fold change)?
0.4-0.6%. 10-fold increased risk with macrosomia
What is the rate of neonatal brachial plexus palsy in the US?
Incidence of both transient and persistent neonatal brachial plexus palsy is 1.5 per 1,000 total births
What is the rate of neonatal brachial plexus palsy (both transient and persistent) in neonates with birth weight > 4500g?
Between 2.6-7%
Can brachial plexus injury occur in the absence of shoulder dystocia? At cesarean birth?
yes and yes
Are most cases of brachial plexus palsy temporary or persistent?
Temporary
What % of cases of brachial plexus palsy resolve by 1 year?
80-90%
Does macrosomia increase risk of being overweight or obese in later life?
yes
Is macrosomia associated with increased rates/prolonged NICU stays?
yes
Does maternal obesity affect the reliability of clinician estimates of fetal weight?
No, we still don’t do great at it no matter the BMI
What is the sensitivity of fundal height for the detection of macrosomia?
20-70% (specificity 90%, better at ruling out)
What is the mean absolute percent error for the Hadlock formula for EFW in newborns weighing >4500g compared to nonmacrosomic newborns?
Non macrosomic : 8%
>4500g : 13%
Do estimations from ultrasound more often over or underestimate actual birth weight?
Overestimate
What inventions have been shown to reduce macrosomia?
Exercise during pregnancy, low glycemic diet in women with GDM, and prepregnancy bariatric surgery in women with class 2 or class 3 obesity.
Does prenatal exercise increase the risk of SGA? Preterm delivery?
No and No
How does prenatal exercise affect the rate of cesarean section?
Decreases by 20%
True or false: addition of insulin to diet therapy for women with GDM decreases the rate of macrosomia?
True
Does bariatric surgery for women with class 2 or 3 obesity decrease odds of having GDM or LGA newborn?
yes to both
True or false: prior bariatric surgery is not associated with an increase in SGA newborns?
False. It is associated. Possibly also associated with increase in preterm delivery
True or false: ACOG supports prepregnancy counseling of morbidly obese patients regarding the benefits and risks of bariatric surgery?
True. Due to the known health benefits, particular for pregnancy outcomes
What is ACOGs stance on induction for macrosomia?
At this time, suspected macrosomia or LGA fetus is not an indication for IOL before 39w0d ass there is insufficient evidence that benefits of reducing shoulder dystocia risk would outweigh the harms of early delivery
Transient brachial plexus palsy occurs in what % of births complicated by shoulder dystocia? What % of these persist at 1 year after birth?
1-17%.
3-33% persist at 1 year
At what EFW cut off would scheduled cesarean section may be beneficial for newborns with suspected macrosomia in women w/ and w/o diabetes?
5000g w/o diabetes
4500g w/ diabetes
However, planned CS for suspected macrosomia is controversial and based on expert opinion
How many CS would need to be performed for suspected macrosomia (>4500g) to prevent one permanent injury in women w/o diabetes? What additional cost would this have to prevent one injury? Compared to a woman with diabetes?
No diabetes: 3,695 cesarean births; $8.7 million additional cost
With diabetes: 443 cesarean births; $930k additional cost
Is suspected macrosomia a contraindication for TOLAC?
No
