Breastfeeding and Maternal Type 1 Diabetes
by Anne Eglash MD, IBCLC, FABM
Breastfeeding, like exercise, demands calories. Women with type 1 diabetes need insulin to control their blood sugars, and if they are expending more energy by breastfeeding, they need to either eat more calories, or reduce their insulin usage to prevent low blood sugars. According to a recent article entitled ‘Breastfeeding at night is rarely followed by hypoglycaemia in women with type 1 diabetes using carbohydrate counting and flexible insulin therapy’ breastfeeding mothers with type 1 diabetes have historically been advised to eat whenever they breastfeed, even in the middle of the night, to prevent a drop in blood sugar.
Medical care for individuals with type 1 diabetes has improved, so is the recommendation to eat overnight still necessary? Many, if not most, healthy type 1 diabetics use insulin pumps, and many more diabetics are using continuous glucose monitoring (CGM), which collects blood sugar information every 5-15 minutes. Unfortunately, use may be dictated by cost and insurance coverage. Now that CGM is available, it is easier for breastfeeding mothers to monitor blood sugar trends overnight to determine if they should eat overnight or lower their basal insulin rate.
The authors of this research study performed continuous glucose monitoring of 33 Danish mothers with type 1 DM for a 6 day period during the 1st, 2nd, and 6th month postpartum. Twenty-six mothers were breastfeeding, 7 were bottle feeding formula, and they compared their blood sugars with 32 control women with type 1 diabetes. All subjects were taught carb counting. Approximately 43-46% of mothers had insulin pumps.
- The type 1 diabetic mothers used an approximate average of 25% less insulin postpartum than they did during pregnancy.
- Breastfeeding mothers spent more time with their blood sugars in the optimal range compared to formula feeding mothers and the control women.
- Breastfeeding mothers used less insulin/kg of body weight as compared to mothers who were formula feeding.
- Only 7% of night time breastfeeds were associated with eating.
- Breastfeeding mothers spent approximately 3-5% of their time overnight with blood sugars less than 72 mg/dl (4mmol/l), which was not significantly different as compared to the control women.
- There was no significant difference in the number of severe hypoglycemic events in the breastfeeding mothers vs the control women.
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Hypoglycaemia in association with breastfeeding is a feared condition in mothers with type 1 diabetes. Thus, routine carbohydrate intake at each breastfeed, particularly at night, is often recommended despite lack of evidence. We aimed to evaluate glucose levels during breastfeeding, focusing on whether night-time breastfeeding induced hypoglycaemia in mothers with type 1 diabetes.
Of 43 consecutive mothers with type 1 diabetes, 33 (77%) were included prospectively 1 month after a singleton delivery. Twenty-six mothers (mean [SD] age 30.7 [5.8] years, mean [SD] duration of diabetes 18.6 [10.3] years) were breastfeeding and seven mothers (mean [SD] age 31.7 [5.6] years, mean [SD] duration of diabetes 20.4 [6.2] years) were bottle-feeding their infants with formula. All were experienced in carbohydrate counting using individually tailored insulin therapy with insulin analogues (45% on insulin pump, 55% on multiple daily injections). Thirty-two women with type 1 diabetes, matched for age ±1 year and BMI ±1 kg/m2, who had not given birth or breastfed in the previous year, served as a control group. Blinded continuous glucose monitoring (CGM) for 6 days was applied at 1, 2 and 6 months postpartum in the breastfeeding mothers who recorded breastfeeds and carbohydrate intake at each CGMperiod. CGM was applied at 1 month postpartum in the formula-feeding mothers and once in the control women. The insulin dose was individually tailored after each CGM period.
The percentage of night-time spent with CGM <4.0 mmol/l was low (4.6%, 3.1% and 2.7% at each CGM period in the breastfeeding mothers vs 1.6% in the control women, p = 0.77), and the breastfeeding mothers spent a greater proportion of the night-time in the target range of 4.0–10.0 mmol/l (p = 0.01). Symptomatic hypoglycaemia occurred two or three times per week at 1, 2 and 6 months postpartum in both breastfeeding mothers and the control women. Severe hypoglycaemia was reported by one mother (3%) during the 6 month postpartum period and by one control woman (3%) in the previous year (p = 0.74). In breastfeeding mothers at 1 month, the insulin dose was 18% (−67% to +48%) lower than before pregnancy (p = 0.04). In total, carbohydrate was not consumed in relation to 438 recorded night-time breastfeeds, and CGM <4.0 mmol/l within 3 h occurred after 20 (4.6%) of these breastfeeds.
The percentage of night-time spent in hypoglycaemia was low in the breastfeeding mothers with type 1 diabetes and was similar in the control women. Breastfeeding at night-time rarely induced hypoglycaemia. The historical recommendation of routine carbohydrate intake at night-time breastfeeding may be obsolete in mothers with type 1 diabetes who have properly reduced insulin dose with sufficient carbohydrate intake.
This is a small study, but there is little recent research on this topic, particularly involving CGM. The findings are similar to an even smaller 2016 study of 8 breastfeeding and 8 control type 1 diabetics.
Older recommendations instructing breastfeeding mothers with type 1 diabetes to eat within 3 hours of breastfeeding no longer seem necessary for women who have adequate knowledge of their blood sugars, and who have the means to carb count and adjust insulin. Even though this study used CGM to evaluate daytime and overnight blood sugars, the mothers were blinded to the CGM results, and many of the mothers relied on carb counting and frequent blood sugar testing to adjust their insulin.
Based on this study, breastfeeding may also confer improved blood sugar control and less insulin usage, as long as mothers have resources to be aware of their blood sugar trends and can adjust their insulin accordingly.
Women who have more difficulty with blood sugar control, don’t have access to CGM or the tools to frequently check their blood sugars, or who struggle to have access to sufficient insulin, may still need to prevent hypoglycemia by eating in association with breastfeeding.