Posts Tagged ‘fetal macrosomia in obese women’

Maternal Obesity from All Sides

June 7th, 2011 by avatar

[Editor’s note:  This is part two of a seven-part series on maternal obesity featuring Kimmelin Hull, UNC-Charlotte Assistant Professor of Kristen Montgomery, childbirth educator and expert blogger on maternal weight issues, Pamela Vireday, from the Well Rounded Mama blog site, and health psychologist, Certified Lactation Consultant (IBCLC) and La Leche League leader,  Kathleen Kendall-Tackett.  To read the first post in this series, go here.]

Complications of Maternal Obesity:  A Closer Look
Let’s examine a few of the individual complications highlighted in yesterday’s post—including their real and purported impact on the perinatal outcome of the mother/fetus(child) dyad, as well as the habitual vs. evidence-based methods for handling these complications in common practice:

Gestational Diabetes
According to Dr. Mahmood’s review, the relative risk ratio of developing GD for an overweight woman is 1.7 compared to her normal weight counterpart.  An obese woman has a 3.6 relative risk of developing GD compared to her normal weight counterpart.  A 2007 meta-anlysis by Chu, et al demonstrated similar results:  odds ratios for developing GD, compared to their normal weight counterparts were 2.14 (overweight), 3.56 (obese) and 8.56 (morbidly obese) (Diabetes Care August 2007 vol. 30 no. 8 2070-2076). The Cochrane Pocket Book –Pregnancy and Childbirth (Cochrane Collaboration and John Wiley & Sons, LTD. pg 92) describes the incidence as affecting between 3 and 6% of pregnancies—that comes out to 30-60/1,000 women.  (Some resources suggest a higher incidence of GD—upwards of 18% of U.S. pregnancies.)

Once a woman has undergone a glucose tolerance test—typically around the 24th – 28th week of gestation—and is deemed positive for gestational diabetes, the question then becomes, “How do we handle this?” The list of information imparted from care provider to patient should look something like this:
1.  Dietary modification
2.  Exercise program
3.  Insulin therapy and/or an oral hypoglycemic agent if the above two measures fail to bring blood glucose levels under control.

Now, there’s a big difference between telling a woman,


“You need to watch your sugar intake, you need to get some regular exercise, and we might have to put you on medication to lower your blood sugar if those first two things don’t work.  If we don’t get this under control, you’re likely to have a big baby that can’t be delivered vaginally…”




“…I’m going to refer you to a registered dietician for dietary counseling so you can learn how to reduce your overall dietary sugar intake and make the best food choices possible, as well as to a physical therapist who can design an appropriate exercise program for you.  If we can decrease your blood sugar levels—preferably without medication—we can decrease other complications associated with gestational diabetes, like too much insulin in his bloodstream and excess growth problems with your baby.”


The latter approach to these talking points could be a good segue into describing how fetuses that are exposed to chronically high levels of blood glucose become newborns with high insulin levels.  Following birth, when baby’s blood sugar levels equalize (faster than insulin levels) the newborn can experience a dangerously rapid hypoglycemia.  This explanation becomes a fact (not judgment)-based reason for motivating the woman to make whatever changes she can during the remainder of her pregnancy.  Because, of course, overweight women care about the well-being of their babies just as much as normal-weight women do.

Additionally, getting a jump-start on treating a pregnant woman’s high blood glucose levels through diet and exercise changes, can also influence her own long term well-being.  Because upwards of 50% of women who experienced gestational diabetes will go on to develop Type II Diabetes later in life (without treatment interventions) guiding a woman toward improving her dietary intake and activity levels sooner, will support a healthier existence, later. (Chu, et al)

However, by taking the short cut and simply telling a woman to ‘eat better and exercise more,’ a lot is being taken for granted:  we are assuming the woman knows about complex carbohydrates and simple carbs and their individual impact on blood glucose levels.  We are assuming she’s aware of the different glycemic loads of different foods.  We are assuming she knows how much constitutes a single serving, what her daily caloric intake is (or should be) and what changes in her diet would be optimal—along with which ones would be risky—for improving her outcome.  In using the former approach, we are also risking making our patient feel bad about her gestational diabetes status.  When people are made to feel ashamed of themselves, they tend to shut down and proverbially stick their fingers in their ears and cry, “Nah-nah-na-nah-nah…I can’t hear you!”  Conversely, giving our patients the tools to make themselves healthier prompts a sense of partnership between consumer and care giver that, ultimately, keeps the lines of communication open.

(More to come on influencing diet and exercise measures–including sociocultural issues– in a later post by Kristen Montgomery.)

Fetal Macrosomia
Both GD and maternal overweight/obesity are predictors of fetal macrosomia as described in this review article, published in the British Journal of Obstetrics and Gynecology (Volume 113, Issue 10, pages 1126–1133).  Unfortunately, suspected fetal macrosomia has been the impetus for elective induction—and sometimes elective cesarean delivery—when recent evidence does not support these practices.

In a cohort analysis of 11,681 deliveries (n=8,379 after inclusion criteria employed) by D.A Beyer, et al, the impact of maternal obesity on labor and delivery was assessed.  The study groups were broken into Control Group (BMI of 18 – 24.9) and Test Group (BMI > 25).  Results described a prolongation of labor of 1.6 hours between the normal weight and obese study participants, and newborn weight differences as follows:

Table 2. Maternal BMI and associated newborn weight

Group (mothers) Weight (newborn)
Control (BMI 18 – 24.9) 3,413g (7.52lb)
Overweight (BMI 25-29.9) 3,535g (7.79lb)
Obese (BMI 30-34.9) 3,508g (7.73lb)
Morbidly Obese (BMI >40) 3,682g (8.11lb)

This study deemed the differences in birth weights listed above as “significant,” as well as other  outcomes, such as shoulder dystocia (n=4—or 0.1%–in the control group, and n=6—or 0.2%–in test group) and primary cesarean delivery (n=975—or 21%–in the control group, and n=1055—or 26%–in the test group).  And yet, I’m not sure that these numbers are significant enough to justify for all obese pregnant women an automatic labor induction or primary c-section due to a 0.1 % increased risk of shoulder dystocia, or a 5% increased likelihood that a secondary cesarean should come to pass.

This cohort study by CSE Homer, et al, out of the UK (n=591) looking at outcomes for planned vaginal versus planned cesarean delivery in extremely obese women (BMI > 50) came to a similar conclusion:
“This study does not provide any evidence to support a policy of routine cesarean delivery for extremely obese women on the basis of concern of higher rates of delivery complications, but does support a policy of individualized decision making on mode of delivery based on a thorough assessment of potential risk factors for poor delivery outcomes.” [my emphasis]  (Under the “Results” section, the study authors describe previous c-section and pre-existing or gestational diabetes as increased risk factors for resultant c-section in the study group.)

Homer et al made an interesting point about should dystocia, in that dystocia is an inexact diagnosis. Some declare a dystocia if they have had to employ a particular maneuver to free the anterior shoulder from the mother’s pubic arch, while others define it as any delay between the delivery of the fetal head and the rest of his body.  This study reported a 2.2% incidence of dystocia in their study population (13/591), compared to general North American and UK rates of ~ 0.6%  and of the study participants in which a should dystocia was diagnosed, none led to lasting morbidities for mother or baby. 30% of the women who had planned a vaginal birth in this cohort went on to deliver by cesarean (slightly higher than the national rate of 24%).  When utilizing a study like this to determine practice guidelines, a clinician has a choice to make:  recommend primary cesarean deliveries for all obese or morbidly obese women because there is some risk of dystocia due to fetal macrosomy, or err on the side of supporting the pursuit of a vaginal delivery unless some other medical indication prompts an alternative decision (the presence of toxemia, for example).

The Cochrane Collabortation weighs in on the issue of elective labor induction to get a baby who is expected to be growing too large for gestational age through and out:  “Induction of labor for suspected fetal macrosomia is not supported with enough data to provide reliable evidence.” (Cochrane Pocketbook, Cochrane Collaboration and John Wiley & Sons, LTD. pg 222)

Statistically, the vast majority of overweight and obese women can deliver their babies vaginally. Barring particular medical complications suggesting otherwise, these mothers should be allowed to pursue a spontaneous delivery if that is their wish.

Many studies anecdotally report high cesarean delivery and induction rates in overweight or obese women yet do not relate the reasons for these outcomes.  Is it possible that provider fear or bias comes into play when an obese woman’s labor and delivery draws near?  Does the slightly longer labor length associated with obese women prompt clinicians to diagnose ‘failure to progress’ sooner than is warranted?  From the Baltimore Sun article referenced in our first post: “People don’t realize the risk we’re taking, by taking care of these patients,” said Dr. Albert Triana, [whose two provider practice does care for women of all sizes].  “There’s more risk of something going wrong and more risk of getting sued.”

Infection During and After Pregnancy for the Overweight or Obese Woman
This May 1st story on ScienceDaily.com brought to light new research out of Tufts University, postulating on the reason pregnant women of size have a harder time fighting off infection.

“Results showed that obese women had fewer CD8+ (cytotoxic T) cells and natural killer cells, which help fight infection, compared to lean women. In addition, obese pregnant women’s ability to produce [other] cells to fight infection was impaired.”  Additionally, recent research out of Guadalajara, Mexico informs us of the impact oxidative stress has on pregnancy:  namely, in the form of preeclampsia, when the oxidative stress reaches peak levels.  When this process progresses, maternal neutrophil levels spike—taxing the woman’s immune system.  Intuitively then, it makes sense that if pregnancy is a high oxidative stress state, (even more so, if pre-eclampsia develops) and obese women have a harder time fighting infection, putting this particular type of patient at an even higher risk for infection (namely via cesarean delivery) should be avoided whenever possible.  At the same time, women for whom cesarean delivery becomes a necessity, should be treated for infection prophylaxis according to their size, rather than standardized adult dosages, suggests new research like this by L. Pevzner et al out of the UC Irvine department of Obstetrics and Gynecology.

In its chilling maternal mortality report (CA-PAMR), the California Department of Public Health spends considerable time discussing the link between obesity and increased risk of both maternal morbidity and mortality.  But the report’s findings are not as simple as stating, ‘all obese women are at an increased risk of dying during our shortly after pregnancy.’  We must remember that not all women of size—whether in California, Colorado or elsewhere in the world—will develop pre-eclampsia, gestational diabetes, cardiomyopathy or other dangerous and potentially life-threatening illnesses.  And yes, larger than “average” women maintain the same types of desires as their leaner counterparts:  to bring forth a healthy baby into the world under the best possible circumstances.  To gain a better understanding of when obesity challenges that potential outcome, we must look at individual circumstances, like those reviewed above, as well as other non-medical factors.

[In tomorrow’s post, we will take a closer look at the CA-PAMR, as well as difficulties caring for obese or extremely obese pregnant women from a care provider’s perspective, and the role preventative medicine and education can take in improving care for this segment of our maternity population.]

Posted by:  Kimmelin Hull, PA, LCCE

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