Case Study: Pregnancy and Early-Onset Type 1 Diabetes Free

C.B., a 24-year-old woman, came to our clinic for a diabetes consultation after being referred by her mother, who is one of our regular patients and has type 1 diabetes herself. The older woman’s diagnosis was made elsewhere 7 years before she sought care with our office and had been based on her lean frame (5% below ideal body weight [IBW] based on height) at presentation and relatively normal insulin sensitivity (insulin requirements have always been <0.5 U/kg/day). No antibody studies or C-peptide levels were done at the time of diagnosis.

Her daughter, C.B., was diagnosed with type 2 diabetes at a community clinic in a rural area near Seattle 3 weeks before her visit with us. The diagnosis was based on her lack of ketones at presentation, “low” presenting blood glucose of 254 mg/dl, and age at diagnosis.

Oral agents were suggested for C.B., but her mother insisted on insulin therapy. Her primary care provider was concerned about this, noting that insulin is rarely the best first-line treatment in patients with type 2 diabetes, but prescribed a temporary regimen for her to use until her appointment with me. At bedtime, she was told to take 2–4 U of NPH, depending on her bedtime blood glucose level, as obtained with home blood glucose monitoring. She was also given a sliding scale for lispro to be taken before eating, depending on her blood glucose readings. If her blood glucose value was <150 mg/dl, she was instructed to take no supplemental lispro.

C.B. received no nutrition information, but her mother taught her carbohydrate counting. They were told that metformin was the treatment choice but would not be started until our office suggested it.

Besides being 3 weeks late with her menstrual period and having some breast tenderness, C.B. had no other symptoms of pregnancy. Her mother was the only family member with diabetes of any type. C.B. and her husband had been trying to conceive for the past 3 months.

On exam, C.B. was a pleasant young woman with a weight of 67 kg and a height of 147 cm (IBW = 65 kg, therefore only 3% over IBW). Except for mild bilateral thyromegally, her physical exam was normal. Her home blood glucose monitoring data were well ordered but revealed chaotic fluctuations, with several readings above 400 mg/dl in the mornings and below 100 mg/dl at midday. Her HbA_1c was 9.2% (normal 4.0–6.0 %). A serum pregnancy test was positive.

1.  How certain is the diagnosis of type 2 diabetes in this patient?

2.  What course of action is indicated in patients presenting with hyperglycemia when pregnancy is diagnosed?

3.  How should C.B. be counseled as to her risk of congenital anomalies if she decides to continue the preg-nancy?

4.  What methods should be used to screen for pregnancy in women with diabetes?

Patients with type 2 diabetes are almost always obese (>20% over IBW). As discussed in a previous issue of Clinical Diabetes by Hansen et al.,1 obesity and family history of obesity are present in virtually all patients with type 2 diabetes. This is perhaps the most important risk indicator when considering the diagnosis. Patients with type 2 diabetes not only have a strong family history of the disease,2 but also frequently have family members with a preponderance of macrovascular conditions.

People with type 1 diabetes are not usually obese and typically do not present with a clear family history of the disease. Often, there is weight loss at diagnosis, which is seldom a feature of type 2 diabetes. Insulin sensitivity is spared, so small doses of insulin produce potent hypoglycemic results. Though not measured in this case, the presence of certain specific antibodies, such as islet cell antibody (ICA) or anti–glutamic acid decarboxylase antibody (anti-GAD₆₄) are common at diagnosis and even diagnostic when hyperglycemia is evident.

C.B. was lean and was aware of no overweight relatives. She and her mother were the only family members with diabetes. Although she did not present with ketones, this is a notoriously bad diagnostic marker. Patients with type 2 diabetes can present with ketones if they have fasted or are seriously ill. Age at diagnosis also is not a reliable marker for either disease, since both types of diabetes can occur in young or older people. Although she had not experienced weight loss, her extreme sensitivity to insulin did not suggest type 2 diabetes. Finally, presenting serum glucose is not always a meaningful diagnostic test to assist clinicians in distinguishing between type 1 and type 2 diabetes.

C.B.’s primary care physician did not know about her plans to conceive a child. The notion that insulin is not usually the best first therapeutic choice in type 2 diabetes is correct in most cases. However, none of the available oral agents is currently approved for use in pregnancy, so insulin was the only option here.

When pregnancy is diagnosed during a period of overt hyperglycemia, hospitalization for rapid metabolic correction is suggested to reduce the rate of spontaneous abortion and fetal anomalies. Hospitalization is, therefore, strongly recommended for all women who present with hyperglycemia at diagnosis of pregnancy. Our patient was advised to proceed immediately to the regional prenatal center, where she was promptly admitted.

Counseling expectant mothers about the risks of fetal malformations and miscarriage is an important, and sometimes grave, necessity. Women who have had poor preconception control of their diabetes are at greater risk of spontaneous miscarriage, and those with sustained hyperglycemia during the first trimester have a higher rate of major malformations.3,4 Brown et al.5 at the University of Washington Medical Center have observed specific risk relationships between presenting HbA_1c level and the risk of poor outcomes. Their preliminary unpublished data, presented in Fig. 1 with permission of the investigators, graphically illustrate the profound effect of hyperglycemia at the time of conception.

1.  Obesity and family history of type 2 diabetes are present in virtually all patients with the disease. They are strong markers. Age, the presence of ketones at diagnosis, and presenting serum glucose are poor indicators.

2.  Every woman with diabetes who is of reproductive age must be counseled about contraception and family planning and asked if there is even the slightest chance she could be pregnant. This should be a part of the interview every time she visits your office.

3.  All women with diabetes who are of reproductive age should be counseled before they are pregnant about the need to optimize metabolic control and plan pregnancy and the risks of spontaneous abortion and birth defects associated with poor metabolic control.

4.  In diabetes, the risks of spontaneous abortion and fetal anomalies are directly related to metabolic control at the time of conception as well as throughout the pregnancy. Hyperglycemia is most destructive to fetal development during the first trimester of gestation.