Metformin fetal development

Pregnancy Metformin and Fetal Development

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Over the last few decades, metformin or glucophage has become the magic pill de jour for PCOS and type 2 diabetes, so much so that prescriptions for metformin across pregnancy are commonplace. Is it safe? To read the majority of research from early 2000 thru 2010 or so, the answer would be an unequivocal yes. Metformin during pregnancy was considered perfectly safe. Indeed, it was more than safe, it was protective against everything from pre-eclampsia to pre-term birth and it reduced the risk for gestational diabetes significantly.

Like all things too good to be true, once the appropriately sized and controlled studies were conducted researchers found that metformin was not safe. In fact, metformin increased the risk for each of the pregnancy complications it was first presumed to protect against; gestational diabetes, preclampsia and preterm labor, and added a few unexpected and more dangerous ones to boot, like an increased risk for maternal pulmonary embolism and fetal neural tube defects. And yet, it is still recommended regularly.

What has never been addressed is fetal health and long term outcomes. How can a drug that alters insulin sensitivity, a critical function in human health, and that crosses the placenta readily, with umbilical cord concentrations at amounts ranging from at least half that of mom’s to far exceeding maternal concentrations, be safe for fetal development? From a purely logical, perhaps even intuitive, gut reaction this makes absolutely no sense.

What are the consequences of maternal metformin on the developing fetus on insulin regulation and pancreatic function, on growth regulation, cardiac function, neurocognitive function and because of the close relationship between insulin and testosterone, on hormone and reproductive function? Certainly, there must be lasting biochemical changes induced during fetal development; what do we really know about the metformin children? Not much, I am afraid.

That’s about it. That’s all we know. Doctors have been giving metformin to pregnant mamas for decades without so much as a sufficiently controlled and conducted study to support its safety or efficacy. Doctors have been prescribing this drug to pregnant mamas despite the limited research. And although animal studies suggest risks to maternal health and in vitro, cell culture studies indicate potential risk to fetal biochemistry, there seems to be no impetus to cease writing prescriptions or do the research necessary to delineate risks versus benefits.


I don’t know about you, but this doesn’t give me a whole lot of confidence in medical science or medical ethics, particularly when one considers the all-too-recent history of thalidomide and DES.

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This post was published here originally on September 26, 2013.  

Image by Pexels from Pixabay.

Chandler Marrs MS, MA, PhD spent the last dozen years in women’s health research with a focus on steroid neuroendocrinology and mental health. She has published and presented several articles on her findings. As a graduate student, she founded and directed the UNLV Maternal Health Lab, mentoring dozens of students while directing clinical and Internet-based research. Post graduate, she continued at UNLV as an adjunct faculty member, teaching advanced undergraduate psychopharmacology and health psychology (stress endocrinology). Dr. Marrs received her BA in philosophy from the University of Redlands; MS in Clinical Psychology from California Lutheran University; and, MA and PhD in Experimental Psychology/ Neuroendocrinology from the University of Nevada, Las Vegas.


  1. What is the alternative though? I tried the herbal substitutes like Berberine and they did nothing for me. I also eat a good diet and walk like 30 KM a week. I just feel when something triggers IR it’s basically impossible to reverse it. Sure, some completely restrictive diets and exercise regimes can temporarily lower insulin and thus improve IR, but they do not cure the issue. Most are also incredibly disordered. And so as soon as you go back to eating a balanced diet and exercising a normal amount, IR comes back.

    Of course it seems worth avoiding metformin during pregnancy, but in general there does not seem to be a good substitute for metformin.

    • Have you consider thiamine? Evidence shows that 70-80% of diabetics, Type 1 and 2 are deficient because they appear to excrete more. There have been studies showing that thiamine supplementation, along with magnesium, its cofactor, improve insulin sensitivity and mitigate a number of the other metabolic issues associated with diabetes. Of course, diet has to be clean too. No amount of supplementation will overcome a bad diet.

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