Gestational diabetes or elevated blood sugar is often treated with metformin to improve blood sugar levels and considered the standard approach to treating gestational diabetes. The research suggests that it has little negative effects on the pregnant mother. However, does significant risks to both mother and baby if the incidence of premature birth count? Here are a few aspects to consider regarding the use of metformin to control blood sugar during pregnancy.
A study of patients receiving a dose of metformin, combination of Clomiphene citrate (CC) and metformin both faired better than CC alone for the induction of ovulation (Neveu, Granger, St-Michel, & Lavoie, 2007). As the combined group showed no benefit compared to metformin alone, one might consider that metformin alone may be considered for the positive effects.
In another study metformin and diet interventions showed a significant outcome compared to non-metformin-diet interventions. The metformin diet showed a reduction of 14 adverse events in a group of 76 expectant mothers, compared to the non-treated group of 36 adverse events out of 76 pregnancies (Glueck et al., 2013).
Thatcher and Jackson (Thatcher & Jackson, 2006) compared pregnancies of 188 women. 61 experienced miscarriages and 11 of those had stopped taking metformin, suggesting other abnormalities beyond metformin’s actions. 81% of women with pregnancies before metformin, 67% had prior miscarriages. 37% of these also miscarried again. Whilst metformin appeared to show minimal effects to mother and foetus 22% were born prematurely.
Whilst metformin has shown favourable outcomes in PCOS states, questions around pertinent biological mechanisms should warrant further discussion. It’s well known that two key endocrine actions may be compromised during the failure to achieve full gestation. Estrogen induces hypoxia in the uterus (Peat, 1997) and failure to produce adequate progesterone to counter the effects of estrogen may be implicated in the commonly fragile time around weeks 9-10 of pregnancy and incidence of miscarriage.
A concern of metformin are its affect transplacentally. Metformin appears to influence testicular size in males and affects sertoli cells. In females it may also lead to decreased androgen synthesis. Birth weight percentile is also significantly lower in pregnancies treated with metformin (Bertoldo, Faure, Dupont, & Froment, 2014)I Metformin has generally appeared safe in expecting mothers but considerable concern should be made regarding its long term effects to offspring and development most notably to reproductive tissues.
Hypothyroidism is a key factor in maintenance of pregnancy and alongside progesterone, thyroid hormone deficiency can be implicated in poor cellular energetics, production of adenosine triphosphate (ATP) and blood sugar regulation. There remains much debate about the issue of subclinical hypothyroidism, values and when to treat and perhaps metformin’s role despite showing some promises may be treating a symptom related to insulin sensitivity.
So perhaps these questions might be more pertinent before prescribing an agent that shows potentially negative effects to the fetus?
- What is the nutrition of the mother, is it enough and does it contain enough nutrients to enhance/maintain adequate progesterone/thyroid production?
- Is estrogen increasing at a rate that suppresses progesterone/thyroid levels and persistently decreases insulin sensitivity?
- Is there enough carbohydrate in the diet to ensure that carbohydrate is effectively utilised instead of persistent conversion of fats, increasing overall stress to both mother and fetus?
- Are the values of hypothyroidism and the identification of subclinical/functional hypothyroid factors appropriate?
- Is gestational diabetes a reflection of the above points?
The use of metformin, without questioning these mechanisms, remains at best a reduced treatment that fails to address a range of biological interactions and function.
Bertoldo, M. J., Faure, M., Dupont, J., & Froment, P. (2014). Impact of metformin on reproductive tissues: an overview from gametogenesis to gestation. Annals of Translational Medicine, 2(6), 55. http://doi.org/10.3978/j.issn.2305-5839.2014.06.04
Glueck, C. J., Goldenberg, N., Pranikoff, J., Khan, Z., Padda, J., & Wang, P. (2013). Effects of metformin-diet intervention before and throughout pregnancy on obstetric and neonatal outcomes in patients with polycystic ovary syndrome. Current Medical Research and Opinion, 29(1), 55–62. http://doi.org/10.1185/03007995.2012.755121
Neveu, N., Granger, L., St-Michel, P., & Lavoie, H. B. (2007). Comparison of clomiphene citrate, metformin, or the combination of both for first-line ovulation induction and achievement of pregnancy in 154 women with polycystic ovary syndrome. Fertility and Sterility, 87(1), 113–120. http://doi.org/10.1016/j.fertnstert.2006.05.069
Peat, R. (1997). From PMS to Menopause: Female Hormones in context.
Thatcher, S. S., & Jackson, E. M. (2006). Pregnancy outcome in infertile patients with polycystic ovary syndrome who were treated with metformin. Fertility and Sterility, 85(4), 1002–1009. http://doi.org/10.1016/j.fertnstert.2005.09.047