PRENATAL CARE AND COUNSELING ISSUES
| UPDATE ON GESTATIONAL DIABETES 2005—Donald R. Coustan, MD, Chace-Joukowsky Professor and Chairman,
Department of Obstetrics and Gynecology, Brown University School of Medicine, Providence, Rhode Island; Obstetrician
and Gynecologist-In-Chief, Women & Infants Hospital of Rhode Island, Providence
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| Definition: carbohydrate intolerance of varying severity with onset or first recognition during pregnancy; United States
Preventive Services Task Force statement—“There isinsufficient evidence to recommend for or against universal
screening for gestational diabetes (GD)”
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 | Maternal: Diabetes Control and Complications Trial (DCCT) showed good control of diabetes lowers risk and rate of
progression of various forms of vascular disease and essential for management of patients; speaker unaware of evidence
suggesting level of glycemia usually seen in patients with GD would have adverse effect on vascular disease;
speaker opines no justification for screening for GD, based on risk of vascular disease to mother; data show ≈40% of
patients with GD developed diabetes within 20 yr by National Diabetes Data Group criteria and 60% by World
Health Organization (WHO) criteria; data show metformin reduced likelihood of development of type 2 diabetes in
patients at high risk for type 2 diabetes, but treatment with lifestyle changes (ie, diet, exercise) superior to pharmacologic
intervention; speaker believes screening for GD beneficial in identifying people who need lifestyle intervention
to reduce long-term risk for diabetes; speaker concludes history of GD powerful predictor for subsequent
development of overt diabetes, but universal screening probably not justified
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| Perinatal morbidity: studies over 20 yr show no increase in perinatal mortality; however, studies involved intervention,
eg, insulin, diet, antepartum testing; Toronto Tri-Hospital Study showed diagnosis as form of intervention has effect
on outcome; speaker believes studies looking at GD should be blinded; older studies suggest undetected GD probably
risk factor for perinatal mortality; forms of morbidity seen in patients with preexisting diabetes occur with
greater frequency in patients with GD; macrosomia—occurs with increased frequency; can lead to traumatic or operative
delivery or shoulder dystocia; GD risk factor for childhood and adult obesity and diabetes; macrosomia most
commonly described problem; patient with GD tends to be older and obese (factors that lead to increased birth
weight); study showed direct relationship between hyperglycemia and neonatal macrosomia, even in thin women;
clear evidence that obesity contributes to macrosomia; glucose independent contributor to macrosomia; study involving
Pima Indians shows childhood obesity and development of diabetes in teenage offspring more common when
mother had hyperglycemia during pregnancy than when she did not
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| Screening and diagnostic testing
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| American College of Obstetricians and Gynecologists (ACOG) 2001 Practice Bulletin—universal screening most
sensitive; low-risk woman less likely to benefit if <25 yr of age, not in high-prevalence racial or ethnic group, body
mass index (weight (kg)/[height (m)]2 ; BMI) <25, no history of abnormal glucose tolerance or diabetes mellitus, no
adverse pregnancy outcomes, and no known diabetes in first-degree relative; recommend 50 g, 1-hr screen at 24 to 28
wk
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| Screening test threshold: 130 mg/dL or 140 mg/dL; 10% less sensitivity with 140-mg/dL threshold; 20% to 21% of patients
require oral glucose tolerance test (OGTT) if 130-mg/dL threshold used and 14% if 140-mg/dL threshold
used; either diagnostic criteria acceptable
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| American Diabetes Association (ADA): screening recommendations same as those of ACOG; alternative option to
skip screening and go directly to OGTT in populations with high prevalence
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| Glucose tolerance test criteria: O’Sullivan and Mahan criteria—fasting 90 mg/dL, 1 hr 165 mg/dL, 2 hr 143 mg/dL,
3 hr 127 mg d/L; Carpenter and Coustan criteria—tests for glucose determination have replaced older methods
and new threshold values calculated by Carpenter and Coustan; fasting 95 mg/dL, 1 hr 180 mg/dL, 2 hr 155 mg/dL,
and 3 hr 140 mg/dL; ADA recommends Carpenter and Coustan criteria; ACOG recommends either criteria
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| Glucose monitoring: daily self-glucose monitoring standard of care for patients with GD
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| Glycemia goals: fasting plasma glucose <95 mg/dL, 1-hr postprandial glucose <130 to 140 mg/dL or 2-hr postprandial
glucose <120 mg/dL
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| Preprandial vs postprandial glucose monitoring: data show patients who monitored postprandial glucose had greater
fall in glycohemoglobin, fewer large for gestational age neonates, fewer cesarean deliveries for cephalopelvic disproportion,
and less neonatal hypoglycemia than patients who monitored glucose preprandially; pregnant patients
should measure glucose postprandially
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| Caloric restriction: associated with decreased weight gain and improved glucose control; patient more likely to become
ketonemic, and adverse fetal effects more common if daily calorie intake <1800
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| Glyburide: second-generation sulfonylurea; data show does not cross placenta and equally effective as insulin in managing
GD; speaker considers glyburide reasonable treatment option
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| Metformin: small molecule; might cross placenta and enhance insulin action in fetus; Physician’s Desk Reference
(PDR)—states not teratogenic in rats and rabbits at doses 2 to 6 times maximum recommended daily exposure;
does not define “partial placental barrier”; package insert states category B drug (in absence of adequate human
studies, animal studies show no fetal risk); speaker does not prescribe category B drugs in pregnancy if not tested in
higher species, eg, dogs, cats, humans; data show significant amounts of metformin can cross placenta; no appropriately
controlled trials in human pregnancy (some case series available); data from Copenhagen show women treated
with metformin had significantly higher risk for preeclampsia and perinatal mortality than women treated with sulfonylurea
or insulin; appears to cross placenta, and fetal effects unknown (“could be good or bad”); well-controlled
studies needed to determine whether safe in pregnancy, improves early pregnancy loss in polycystic ovary syndrome
(PCOS), and prevents GD in PCOS; available data do not support use of metformin in pregnancy, except with fully
informed consent
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| Obstetric management: induction not associated with higher cesarean delivery; speaker induces patient with GD at
term; postpartum follow-up—check for presence of DM or impaired glucose tolerance at 6-wk postpartum visit
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| Nonpregnant diagnostic criteria: diabetes—fasting plasma glucose >125 mg/dL on ≥2 occasions or ≥200 mg/dL 2 hr
after 75-g load; prediabetes—impaired fasting glucose 100 to 125 mg/dL or 2-hr value on 75-g OGTT 140 to 200
mg/dL
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| FACTS AND MYTHS IN PRENATAL CARE —Amy M. Autry, MD, Professor, Department of Obstetrics, Gynecology
and Reproductive Sciences, University of California, San Francisco, School of Medicine
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| Introduction: superstition and post-tonsillectomy hemorrhage—post-tonsillectomy hemorrhages do not occur in clusters
of 3 and not more frequent with full moon or on Friday the 13th ; bleeding rate among children with red hair similar
to that of nonredheaded children
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| Fish: accumulates methylmercury which is neurotoxic; signs of toxicity in adults widespread, eg, visual disturbances,
motor and speech problems, mental health disturbances, seizures; signs in children mimic cerebral palsy, ie, inability
to walk unassisted or respond to verbal commands by 2 yr of age, microcephaly, and seizures; majority of mercury
emissions come from industrial coal-burning plants currently unregulated; deposited in streams and oceans
where bacteria transform mercury into methylmercury; methylmercury ingested by fish; higher levels in smaller
fish; 100% of human exposure comes from dietary consumption; absorbed rapidly in gastrointestinal (GI) tract; red
blood cells (RBCs) redistribute; brain primary target for toxicity; mercury has affinity for fetal hemoglobin; mercury
level in fetus ≈25% higher than in mother; exposure to methylmercury in fish in Japan and contaminated grain
in Iraq caused epidemic poisoning
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| Reference dose (Rfd): estimated amount of substance that can be ingested daily over lifetime without adverse effects;
0.1 µg/kg body weight per day; WHO and Food and Drug Administration (FDA) estimates 0.48 µg/kg per day; Environmental
Protection Agency (EPA) estimates 1% to 3% of women exposed; Centers for Disease Control and Prevention
(CDC) estimate 6% of women consume enough fish to be above EPA Rfd; higher levels noted in women
from Canada and United States (around Great Lakes); levels vary in fish in different bodies of water
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| Joint FDA/EPA consumer advisory, 2004: do not eat shark, swordfish, king mackerel, or tilefish; avoid fish that eat
other fish; eat up to 12 ounces (2 average meals) per week of variety of fish and shellfish low in mercury, eg, shrimp,
crab, salmon, catfish; check local advisories about safety of fish caught locally; advisory emphasizes positive benefits
of eating fish; mercury level lower in canned light tuna than in albacore tuna; recommend eating albacore tuna only
once weekly; eat local fish only once weekly if recommendation cannot be found
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| Listeriosis: ≈1500 cases in the United States annually, resulting in 500 deaths; immunocompromised patients and pregnant
women more susceptible; pregnant women 20 times more likely to become infected; one third of cases occur in
pregnant women; infection more severe early in pregnancy; miscarriage or stillbirth in 20% of women who become
infected; can result in sepsis and meningitis in neonate; presenting symptom flu-like syndrome
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| FDA and United States Department of Agriculture (USDA) advise: no hotdogs or luncheon meats unless reheated to
steaming; no soft cheeses; no refrigerated pates or meat spreads; no refrigerated smoked seafood; no raw (unpasteurized)
milk
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| Caffeine: stimulant; rapidly enters central nervous system; causes transient increase in blood pressure and pulse; increases
urination; substantially less caffeine in soft drinks than in coffee; caffeine level varies among types of coffee;
less caffeine in instant coffee; more caffeine in imported coffee and tea; less caffeine in green tea than black tea; less
caffeine in milk chocolate than dark chocolate; no substantiated data showing moderate caffeine use associated with
adverse pregnancy outcome; studies involving low birth weight neonates and miscarriage confounded by cigarette
smoking, which is heavily concentrated in caffeine drinkers; most likely, no problem with moderate to low caffeine
consumption
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| Alcohol: 10% of pregnant women use alcohol; 1% engage in heavy drinking, and 2% engage in binge drinking; of
women not using birth control method, >50% use alcohol and >12% engage in binge drinking
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| Fetal alcohol syndrome (FAS): triad of short stature, pervasive neurocognitive defects, and facial dysmorphology of
short palpebral fissures, flattened philtrum, and thin upper lip vermillion; CDC estimates ≈6000 babies born annually
with FAS and ≈3 times that number have some form of spectrum disorder (less severe than syndrome); considered
foremost preventable neurobehavioral problem in pregnant women in the United States; data poor on moderate
or light drinking; data show persistent differences in growth parameters (head circumference, height, and weight)
and delinquent behavior in children of women drinking even <1 drink per wk; no level proven safe in pregnancy
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| Hot tubs: hyperthermia associated with teratogenicity in animals; potential teratogenic temperature 38.9ºC (l02.2ºF);
takes 15 min to reach potential teratogenic temperature if hot tub 102.2ºF, 10 min if 106.0ºF; miscarriage and neural
tube defects of concern with hyperthermia; poor data on first trimester miscarriage; pathophysiology connected with
hot tubs and miscarriage unknown
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| Exercise: ACOG recommends pregnant women exercise 30 min per day; only 16% of pregnant women get recommended
amount of exercise, compared to 26% of nonpregnant women; benefits—prevention of GD, potential effect
on preeclampsia and premature labor, and decreased postpartum depression
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| ACOG recommendations: avoid supine activity and motionless standing; avoid sports with high potential for contact
or falling; no scuba diving (potential for decompression sickness in fetus); exertion at high altitudes appears safe; no
reports that hyperthermia associated with exercise teratogenic; data show marathon runners who continue to run
have lighter babies (but still in normal birth weight range) and decreased body fat (persists through 5 yr of age); associated
with improved intelligence and language skills scores in offspring
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| Hair dye: no data suggesting teratogenic effects or association with cancer
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Educational Objectives
| The goal of this program is to educate the listener about gestational diabetes (GD) as well as health and safety issues in
pregnancy. After hearing and assimilating this program, the clinician will be better able to:
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| 1. Discuss the rationale in screening for GD and the impact of GD on the mother and fetus.
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| 2. Describe the basis for blood glucose testing in women with GD, and summarize the difference between 2 glucose
tolerance test criteria.
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| 3. List the glycemia goals for women with GD.
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| 4. Manage patients with GD.
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| 5. Counsel patients about food safety and lifestyle issues in pregnancy.
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Discussed on This Program
Glyburide (glibenclamide) [DiaBeta, Glynase PresTab, Micronase]
Metformin HCl [Fortamet, Glucophage, Glucophage XR]
Suggested Reading
Coustan DR: Making the diagnosis of gestational diabetes mellitus. Clin Obstet Gynecol 43(1):99, 2000; Gabbe SG et
al: Management of diabetes mellitus complicating pregnancy. Obstet Gynecol 103(3):586, 2004; Grosso LM et al: Caffeine
metabolism, genetics, and perinatal outcomes: a review of exposure assessment considerations during pregnancy.
Ann Epidemiol 15(6), 2005; Leviton A et al: A review of the literature relating caffeine consumption by women to their
risk of reproductive hazards. Food Chem Toxicol 40(9):1271, 2002; Li DK et al: Hot tub use during pregnancy and the
risk of miscarriage. Am J Epidemiol 158(10):931, 2003; Lu GC et al: Screening for gestational diabetes mellitus in the
subsequent pregnancy: is it worthwhile? Am J Obstet Gynecol 187(4):918, 2002; Kjos SL et al: Insulin-requiring diabetes
in pregnancy: a randomized trial of active induction of labor and expectant management. Am J Obstet Gynecol
169(3):611, 1993; Metzger BE et al: Summary and recommendations of the Fourth International Workshop-Conference
on Gestational Diabetes Mellitus. The Organizing Committee. Diabetes Care 21 Suppl 2:B161-7, 1998; McCarthy EA
et al: Meformin in obstetric and gynecologic practice: a review. Obstet Gynecol Surv 59(2):118, 2004; Naylor CD et al:
Cesarean delivery in relation to birth weight and gestational glucose tolerance: pathophysiology or practice style? Toronto
Trihospital Gestational Diabetes Investigators. JAMA 275(15):1165, 1996; No authors listed: Eating safely during
pregnancy. J Midwifery Womens Health 49(4):373, 2004; Moretti ME et al: Maternal hyperthermia and the risk for
neural tube defects in offspring: systematic review and meta-analysis. Epidemiology 16(2):216, 2005; Okah FA et al:
Term-gestation low birth weight and health-compromising behaviors during pregnancy. Obstet Gynecol 105(3):543,
2005.
Faculty Disclosure
In adherence to ACCME guidelines, the Audio-Digest Foundation requests all lecturers to disclose any significant financial
relationship with the manufacturer or provider of any commercial product or service discussed. For this issue, the
faculty reported nothing to disclose.
Dr. Coustan was recorded at the Medical University of South Carolina’s 36th Annual OB/GYN Spring Symposium: Azaleas,
Dogwoods and Conditions Complicating Pregnancy, held on April 4-6, 2005, in Charleston, South Carolina. Dr.
Autry was recorded at Antepartum & Intrapartum Management, sponsored by University of California, San Francisco,
School of Medicine, and held on June 9-11, 2005, in San Francisco. The Audio-Digest Foundation thanks the speakers
and the sponsors for their cooperation in the production of this program.
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