Pregnancy profoundly affects carbohydrate metabolism. These changes are
important in women with diabetes typically type 1, but an increasing number
of young type 2 patients are being encountered) who are lanning pregnancy,
and in women who develop gestational diabetes mellitus (GDM) - glucose
intolerance first recognized during pregnancy. In all cases, a comprehensive
approach involving expertise in obstetrics, diabetology, nursing and dietetics is
highly desirable.
Pre-pregnancy
Good glycaemic control before pregnancy is essential, and maintenance of
such control gives the greatest likelihood of a successful outcome. Pre-
pregnancy evaluation is preferred to assess diabetes complications and the
risk to the mother, to review glycaemic control and the insulin regimen, and to
discuss the implications for the fetus.
Active proliferative retinopathy should be treated before pregnancy.
Proteinuria increases the risk of reeclamptic toxaemia and hypertension, and
requires close monitoring. Pre-pregnancy elevated creatinine is more serious,
and is associated with intrauterine growth retardation, pre-eclamptic
toxaemia, and rogression of the mother`s retinopathy.
Autonomic neuropathy involving gastroparesis is usually very difficult to
manage. Severe ypertriglyceridaemia is a concern because fibrates are not
recommended during pregnancy and triglyceride levels rise during pregnancy,
increasing the risk of acute pancreatitis. Intensive insulin therapy (four or five
injections per day) and intensive glucose monitoring(four times per day) are
required.
Intensive insulin therapy is associated with a higher risk of hypoglycaemia.
The sudden improvement in glucose control with intensive insulin therapy may
aggravate the progression of retinopathy already accentuated by pregnancy,
but this risk should not alter the goal of good glycaemic control.
Folic acid supplements (minimum 0.4 ㎎/day) are initiated and rubella status
is checked. In women with type 2 diabetes, oral hypoglycaemic agents are
replaced with insulin. Oral hypoglycaemic agents are not recommended in the
first trimester. Patients with type 2 diabetes typically need large doses of
insulin later in pregnancy, and it is best that they learn about insulin
adjustments pre-pregnancy rather than during the pregnancy.
Pregnancy
Regular follow-up is essential, involving all team members (diabetes nurse,
dietitian, physician and obstetrician with a special interest in diabetes in
pregnancy).
· Ultrasound evaluation for gestational age and initial assessment for any
possible congenital malformations is needed at the end of the first trimester.
Insulin requirements may decrease slightly if the woman has morning
sickness, but hypoglycaemia does not appear to harm the fetus.
· In the second trimester, the focus on glycaemic control is maintained, with
regular checks for hypertension, proteinuria and retinopathy. Extra calories
(170/day) are required, and insulin requirements increase(typically after 16
weeks) and need continual revision.
· In the third trimester, more attention is focused on monitoring for pre-
eclampsia. Insulin requirements continue to increase, usually reaching a
plateau at about 36 weeks` gestation. A decrease in insulin requirements of
more than 10% warrants closer fetal monitoring. Consensus statements
recommend routine monitoring of fetal well-being using nonstress tests or
modified biophysical profiles from 32 weeks, and fetal movement counts are
easy and worthwhile.
Labour and Post-partum
Routine Caesarean section is not required, and delivery should not be
induced before 40 weeks` gestation unless an indication arises. Subcutaneous
insulin is continued until active labour is established, then separate infusions
of insulin and glucose are preferred to maintain euglycaemia. Hyperglycaemia
during labour is associated with neonatal hypoglycaemia. Once the placenta is
delivered, insulin is discontinued. Intravenous glucose is continued until the
patient is able to eat and drink normally.
GESTATIONAL DIABETES
MELLITUS
Normal pregnancy is associated with increasing insulin resistance and
associated hyperinsulinaemia. GDM ensues if there is inadequate insulin
reserve. It occurs in 2 to 4% of pregnancies, usually late in the second
trimester, is typically mild, and is associated with a risk of macrosomia,
neonatal hypoglycaemia and jaundice in the fetus, and a long-term risk of
diabetes in the mother.
There is debate about the significance of GDM. Macrosomia has many
possible causes including maternal obesity, paternal size, maternal weight
gain and hyperglycaemia, but only the latter is modifiable during pregnancy.
Cost:benefit analyses support the value of detecting and treating GDM, but a
label of `GDM` may lead to unnecessary Caesarean section irrespective of fetal
size, and should be avoided.
Screening and Diagnosis
When assessing women for GDM, 50% of cases are missed if the classical
risk factors only are used. In North America, universal screening using a 50-g
glucose challenge is recommended in all pregnant women at 24 to 28 weeks`
gestation, unless the woman is in a very low-risk group; a glucose level of 7.8
mmol/L or more 1 hour later prompts an oral glucose tolerance test(OGTT). A
high glucose level postscreen(e10.3 mmol/L) suggests a diagnosis of GDM with
96% probability. GDM in early pregnancy suggests pre-existing diabetes. In
this setting, measurement of HbA1c aids assessment of the risk of congenital
malformations.
These patients are at high risk of continuing diabetes postpartum.
There is no universal agreement on diagnostic criteria and each country has
its own guidelines. In the UK, the WHO guidelines are used(2 hours post-75-g
OGTT e7.8 mmol/L). In Canada, a 75-g OGTT is performed and GDM is
diagnosed if two out of three values exceed the cut-off levels(fasting 5.3
mmol/L, 1 hour 10.6 mmol/L, 2 hours 8.9 mmol/L).
Management of GDM
Once GDM is diagnosed, diet counselling and glucose monitoring are
initiated. Patients are instructed to measure their glucose four times per day.
Fasting and 1-hour or 2-hour postprandial glucose levels are used.(Whether 1-
hour or 2-hour determinations are used is based on the degree of abnormality
of the OGTT at these time points.) Target levels are fasting less than 5.3
mmol/L, 1 hour less than 7.8 mmol/L and 2 hours less than 6.7 mmol/L. If
these levels are intermittently exceeded, attention to diet or modest exercise
such as walking after meals may suffice. If they are consistently exceeded,
insulin is required. Glyburide does not cross the placenta and thus is an
alternative, but such pharmacological therapy may lack some of the dosing
and timing specificity of insulin.
Short-acting insulin(regular) pre-meal, and intermediate-acting insulin(NPH)
at bedtime if required, is started at doses of 4 units; this treatment is
acceptable to most patients, who are readily taught how to adjust the dose to
attain good glycaemic control.
Shortacting insulin analogues have no specific advantage, but are indicated
when 1-hour postprandial hyperglycaemia is the main problem or when
delayed hypoglycaemia occurs with large doses of soluble insulin. The need for
fetal monitoring is proportional to the severity of GDM; stable, diet-controlled
GDM needs no special monitoring, but women taking large doses of insulin(> 1
unit/㎏/day) are monitored as for type 1 patients.
■ 기사 요지
본지 자매지인 `Journal of Pediatrics, Obsterics and Gynecology(JPOG)`에 게재된
글로 `당뇨병과 임신`이 주내용이다.
임신은 탄수화물대사에 큰 영향을 미치는 만큼, 임신을 계획중인 당뇨병 여성에게는 세심
한 주의가 요구된다. 임신전에는 혈당량 조절이 가장 중요하다.
이외에 증식성당뇨병성망막증 치료·단백뇨 모니터링·집중적인 인슐린 치료 등이 선행돼야
한다. 제2형당뇨병 여성의 경우, 인슐린 대신 경구용 혈당강하제가 필요하며 임신후에는 고용
량 인슐린 치료가 요구된다.
임신초기는 기형아의 가능성 확인을 위해 초음파검사가 필수적이다. 아침병(morning
sickness)이라 불리는 입덧이 심한 경우 인슐린을 줄여야 하나, 저혈당이 태아에게 손상을 주
지는 않는다. 임신중반기에는 고혈압·단백뇨·망막증과 함게 혈당량 조절에 초점을 맞춘다. 임
신후반기에는 전자간증(pre-eclampsia) 가능성에 대비한다. 정리·이상돈 기자
sdlee@kimsonline.co.kr