Science You Can Use: Could taking metformin in pregnancy increase breastfeeding success of women with PCOS?

Hormonal causes of low milk supply are, in my mind, the final frontier of our understanding of milk supply problems.

We know a lot about the normal course of lactation in women without hormonal or metabolic imbalances, and how to protect and rebuild milk supply when one of many Booby Traps drives things off course.  But for those who do have hormonal imbalances and suffer milk supply problems, we know too little and have too few solutions to offer.

So I was very interested to see a new study published this year by a Norwegian research team investigating the effect of metformin use in pregnancy on breastfeeding outcomes among women with Polycystic Ovary Syndrome (PCOS).

PCOS, a hormonal imbalance affecting as many as 15% of all women, has for some time been implicated in milk supply problems.  But it’s a slippery issue – some women with PCOS have dramatic milk supply problems, some don’t, and some even have an oversupply.  The theory of its effect on lactation is that – in some cases – it may cause the underdevelopment of the breast during pregnancy (and possibly even in puberty), making less glandular tissue available for milk production and resulting in low milk supply.

One hope has been if that women took metformin, a drug which reduces PCOS symptoms, during pregnancy, they might be more likely to experience normal breast growth, setting them up to then develop a full milk supply.

The study published this year, an offshoot of a larger randomized trial (metformin vs. placebo), looked for associations between metformin use during pregnancy and 1) breast size growth, and 2) duration of breastfeeding among 186 women with PCOS.  It found:

There were no differences in the duration of exclusive breastfeeding or the duration of partial breastfeeding between mothers with PCOS treated with metformin and those treated with placebo.

There were no differences in breast size before pregnancy or breast size increment during pregnancy between the metformin and the placebo groups.

The duration of both exclusive and partial breastfeeding correlated positively with breast size increment in pregnancy.

Here are two other interesting findings:

Increased BMI (body mass index) [pre-pregnancy] was related to a shorter duration of breastfeeding.

Women with no breast size increment [growth] had higher blood pressure, were more obese, had higher fasting insulin and triglyceride levels already at inclusion in the first trimester of pregnancy, compared with those who experienced breast size increment.

I asked Lisa Marasco, IBCLC, author of The Breastfeeding Mother’s Guide to Making More Milk and expert on the hormonal causes of low milk production, for her comments (see my podcast interview with her on hormones and low milk supply).

She told me that her contention has been that metformin will help optimize breast development for breastfeeding, and that while this study didn’t confirm that, it may not have been a large enough sample.  She noted that she has seen a number of individual cases in which changes are reported.  She also noted two important findings:  1) women with PCOS who experience milk supply problems are likely more metabolically disturbed, and 2) women with fewer breast changes during pregnancy were more likely to have problems with milk production.

So this study’s results are disappointing, but they also raise many questions:  Did the women who had breast growth have it because they were taking metformin or because they were less meatoblically distrubed and were going to have normal breast growth anyway?  Would the women who were more metabolically disturbed have had breast growth if the dose had been higher?  Is it something about obesity (much more common among women with PCOS) which is causing milk supply problems?

And what if these moms had been taking metofrmin both in pregnancy and during lactation, instead of ending in pregnancy?  There are no studies of this beyond case reports.

Remember how I called the hormonal causes of low milk supply the final frontier?  For the estimated 15% of women who have PCOS, I’m grateful that this is an active area of research.

Do you have PCOS?  Did you have breast growth in pregnancy?  Did you take metformin ih pregnancy and/or lactation?  How has PCOS and/or metformin impacted your breastfeeding experience? 

Image credit:  Wikimedia Commons

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5 Comments | Last revised on 12/12/2012

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