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Ronnie Falcao, LM MS, a homebirth midwife in Mountain View, CA

Notes from a GDM presentation by Steven Gabbe, M.D. in 1990

I posted last week about a presentation about GDM testing; here is a summary of the presentation:

Presenter: Steven Gabbe, M.D. (for those of who don't know the name, he is the author of a respected OB textbook and generally a well-recognized academic and clinical OB.

Part 1: Information from the Third International Workshop Conference, 1990:

Why screen?
To find those that need insulin, because they suffer the greatest perinatal mortality.

He presents a table from Cassady, G et al. Am J Obstet Gynecol 122:13 1979

124 Class A diabetics (diet controlled -- normal fasting and post prandial glucose)

Perinatal Mortality: 3 = 24.2/1000
Macrosomia: 17%

24 diabetics labeled Class A who were actually Class A2 (needed insulin because their fasting and/or postprandials were elevated). He doesn't explain why these women were misdiagnosed and why their insulin requirement was overlooked.

Perinatal Mortality: 4 = 190.5/1000 (this is eight times higher than the really truly Class A group)
Macrosomia: 38% (more than double)

This was his whole point of the presentation: that we should tighten up screening cutoffs, provide sound nutritional counseling to all GDMs, maintain strict home glucose monitoring, and provide insulin for those who's fasting is > 95mg/dl and/or who's 2 hour PP is > 120 mg/dl because this will reduce complications and lead to better outcomes

[Notetaker's Comments: I know that many midwives are angry that so many women get put into the category of GDM and protest putting women through an unpleasant series of tests, and therefore will be resistant to the notion that we should be MORE vigilant in identifying glucose intolerance in pregnancy.

However, IMHO we should not undertake greater surveillance so as to label more pregnant women as "high risk", because it is becoming clearer and clearer that when diet-control is sufficient (fasting and postprandials are normal) women and their babies have good outcomes. But as is evidenced by the study quoted above, when a woman is actually requiring insulin and for whatever reason her care providers don't know that she does, she and her baby are at very high risk of complications and we have a responsibility to find those few women in our obstetric populations and PREVENT fetal disability and death.

I understand the desire to avoid testing that has such a high false positive rate (only 15% of women with abnormal GCTs will have an abnormal GTT), and our clients can certainly opt to not test, IF they are fully informed as to the nature of the disease and it's subtle presentation and the potential risks. Heck, I have clients who won't do the metabolic screening of their kids. They know what it is for, they understand the prevalence of the diseases, the consequences if their child has one of them and it is not detected through screening. Can't tie the kid down and draw the blood, can I??? ]

Part II: Management of GDM & glucose monitoring

59 Class A Controls (no home monitoring. he doesn't state whether or not the provider was monitoring their glucose control, but it appears from the results that they were, probably the recommended weekly fasting and 2 hour PP)
Rate of Macrosomia: 24% = 14 cases (does not detail definition of macrosomia)
Needed Insulin: 21% = 5 cases

58 Class A Treatment: unspecified number of daily glucometer readings at home
Rate of macrosomia: 9% = 5 cases
Needed Insulin: 50% = 29 cases

[Notetaker's Comments: OK, so the group that tested their sugars at home were much much more likely to be identified as requiring insulin for better glucose control, BUT their outcomes show a more than 50% decrease in macrosomia, one of the major complications of GDM which leads to more cesareans and all the attendant risks of surgery, etc.]

Intensified = 7 daily home glucose reading with meter. 
Conventional = 4 times daily visual. 

Conventional (n=1,316 women)
Insulin requiring = 34%
Macrosomia (>4000 gms) = 13.6%
Primary Cesarean = 19%
Shoulder Dystocia = 1.4%

Intensified (n=1,145 women)
Insulin requiring = 66%
Macrosomia = 7.1%
Primary Cesarean = 13%
Shoulder Dystocia = 0.4%

note: all results were significant to a p<.01

[Notetaker's Comments: so this large study has dramaticly better outcomes in the more intensely monitored GDMs, with a significant reduction in macrosomia, cesarean delivery, and shoulder dystocia -- and a concomitantly much more frequent use of insulin.]

1. Allow to go to term (see, no recommendation for early induction)
2. At 40 weeks, begin bi-weekly NSTs
3. Evaluate for cesarean delivery if EFW > 4250 gms
4. Treat Class A2 (insulin requiring GDM) as you would a pre-gestational diabetic) ie. NST and BPP starting at 32-34 weeks, etc.

Values for home monitors compared to plasma
                         Capillary result                   Plasma result
Accu-check II                  160                                135
Accu-check III                 155                                135
One Touch II                   120                                140

[Notetaker's Comments: which says to me that we better be REAL careful with the results from home monitoring and follow up with regular fasting and 2 hours sent to a lab, particularly when making the decision to use insulin therapy.]

Jovanovic-Peterson L. et al Am J Obstet Gynecol 1989 161:415-419

Screening: (this was hand-written by me on the back of the syllabus, so I don't know if it was his opinion or an official ACOG criteria)

Women who do not need GCT screening:

1. < 25 years old
2. Normal body weight for height
3. No first degree relative with Type II (adult onset) diabetes
4. Not Hispanic, African American, or Asian (because these groups have higher rates)

1. 15% of women will have an abnormal GCT
2. 15% of those will have an abnormal GTT
3. 15% of those will require insulin
4. 15%of GDM will have macrosomic baby
5. 15% of GDM will have future impaired glucose tolerance or diabetes.

I am very conflicted, as I am sure many of the midwives on this list are. My clients mostly hate the testing. I am horrified that I have to subject a pregnant woman to fasting and then a huge sugar load when only 15% of abnormal GCTs end up diagnosed GDM.

Then again, I buy the argument that some of those who truly are glucose intolerant are at higher obstetrical risk, but when we have to put a woman on insulin she can no longer give birth at the center, which is usually very upsetting news (thankfully we have privileges at the backup hospital and can still attend them, but the loss of the nice birth center birth dream is painful for many of our clients).

And I realise that midwifery is not just about people having a wonderful birth experience, it is also appropriately using knowledge and technology to wherever possible maximize the chances of a healthy outcome. So, it is too bad that women don't like the testing or that they get thrown out of the birthcenter if their sugars aren't well controlled -- it is better than a dead baby or an unnecessary cesarean, right? I still feel terribly conflicted.

And I also realize that these issues bear even more weight for homebirth practitioners and non-legal midwives. If one of these practitioners identifies a woman as GDM, she may have to leave the practice all together and then might face all kinds of other complications at the hands of the mainstream OBs (ie inappropriate induction, unnecessary cesarean, etc, etc), especially if the OB knows or suspects the woman started her care with a non-licensed practitioner or was planning a home-birth (or god-forbid thinks the woman was irresponsible enough to get to 30 weeks with no prenatal care if she doesn't disclose). ]