Diabetes and lactation

1. Lactation is associated with 30% decreased risk of the woman developing Diabetes Mellitus Type 2 (T2DM) later in life. This is true whether or not the woman has Gestational Diabetes Mellitus (GDM).

2. Diabetes Mellitus Type I (T1DM) and GDM are linked with delayed onset of lactation (or delayed onset of secretory activation). Diabetes-associated delayed onset of lactation is more likely if the woman is

   • Primip

   • Older than 35 years

   • Living with obesity

   • On insulin treatment

   • With poor metabolic control.

3. T2DM is linked with

   • Delayed onset of lactation (higher insulin doses are associated with later secretory activation)

   • High rates of neonatal hypoglycaemia

   • High rates of formula supplementation.

4. It is safe for women with GDM to express colostrum antenatally, from 36 weeks.

   • Antenatal expression of colostrum typically involves 3-5 minutes of hand expressing each breast, 2-3 times daily, from 36 weeks.

   • 25% of women are unable to express antenatally but this doesn't predict that they'll have low milk supply postpartum.

   • Antenatal expression of colostrum is linked with delayed formula use in the first week post-birth. This could be explained by staff feeling more confident to delay formula use when there is stored colostrum avaiable.

   • Antenatal expression has not been shown to improve breastfeeding outcomes.

5. Moorhead et al 2024 showed that women with any diabetes in pregnancy are at a higher risk of delayed onset of secretory activation (58.6% with compared to 46.9% without). You can find out about delayed onset of secretory activation here. However, delayed secretory activation is common using the 72 hour definition (46.9%) and by far the majority of women with diabetes in pregnancy won't have delay of secretory activation. Effective intervention for the most common causes of breastfeeding difficulty, regardless of history of diabetes in pregnancy, is fundamental, and yet remains a health system blind spot.

6. Here are some useful things to know about T1DM and lactation.

   • Insulin requirements may fall as much as 30-50% after delivery of the placenta, and may remain 20% lower than pre-pregnancy for first four months post birth (with wide individual variation).

   • Hourly blood glucose (BSL) levels are required post-birth until first meal.

   • No bolus of insulin should be given with first meal due to tendency to hypo.

   • BSLS are a moving target for 3-5 days postpartum, usually requiring endocrinologist supervision.

   • Aim for 5-10 mmol/L as a general rule in the postpartum, with plenty of hypo snacks available.

Polycystic Ovary Syndrome (PCOS) and lactation

1. Considerations of PCOS management have a big overlap with obesity and weight management.

2. There are marginal differences in breastfeeding duration in PCOS cf non-PCOS women (median complete duration 7 vs 9 months).

3. The main independent predictor of breastfeeding initiation and duration in women with PCOS is BMI.

   • The links between PCOS, insulin resistance, and the effects of higher androgen are still being elucidated.

   • There is a link between PCOS and breast hypoplasia and Insufficient Glandular Tissue.

4. There is currently no role for use of metformin as a galactogogue. However, if it is being taken for diabetes or PCOS it may be safely continued during lactation.

Recommended resources

Royal Women's Hospital, Victoria, online instructions for collection of antenatal colostrum: here

Monash 2023 Evidence based Guidelines for Polycystic Ovary Syndrome: here

Moorhead A, Forster DA, Donath SM. Does antenatal expressing affect onset of lactogenesis for women with diabetes? Results from a randomised controlled trial and cohort study. ANZJOB. 2024:https://doi.org/10.1111/ajo.13929.