Maintaining optimal health during pregnancy is essential for a healthy pregnancy and birth, but it might be more challenging for some than for others.

Those who enter pregnancy with pre-existing diabetes, or who develop gestational diabetes mellitus (GDM) in pregnancy, might need to take additional steps to keep themselves and their babies healthy throughout.

Type 2 diabetes mellitus occurs when the body doesn’t produce enough insulin, or when the insulin that is produced is not effective in managing the body’s blood sugar levels. This is known as insulin resistance. Gestational diabetes mellitus is a form of diabetes that develops only in pregnancy.

Metformin while pregnant

Metformin is often the preferred first line pharmacological treatment for gestational diabetes and type 2 diabetes, if following dietary and lifestyle advice has not been effective in controlling blood sugar levels.

It’s important to make sure blood sugar levels are controlled during pregnancy, to prevent pregnancy and birth complications and to improve maternal and neonatal outcomes.

Uncontrolled diabetes, whether it is type 2 or gestational diabetes, can have adverse pregnancy outcomes for both the mother and the baby as well as during birth and in the postpartum period.

Effects of uncontrolled diabetes in pregnancy include a number of increased risk factors:

Miscarriage
Preterm birth
Gestational hypertension and pregnancy-induced hypertension
Birth defects
Still birth and neonatal death
Increased birth weight and large for gestational age babies
Birth complications, such as shoulder dystocia and birth trauma
Neonatal hypoglycemia
Admission to neonatal unit.

Will metformin affect my baby?

It is well known that insulin resistance and maternal hyperglycemia can have significant pregnancy complications, with adverse outcomes for both pregnant patients and their babies. Therefore it’s vital to do whatever is possible to keep levels in check.

Recent studies have found no increased risk in neonatal mortality, hypoglycemia or major congenital abnormalities, or challenges in social-motor development for babies born to women taking metformin, compared with those taking insulin.

Research has found that pregnancy outcomes in women who were treated with metformin alone demonstrated a lesser incidence of prematurity, neonatal jaundice and admission to neonatal unit, with an overall improvement in neonatal morbidity.

It is important to note that, unlike insulin, metformin is known to cross the placenta freely, and reach your unborn baby. What is less well known is the potential long term effect of intrauterine metformin exposure for the child.

One study showed there was a significant reduction in birth weight for infants born to mothers in the metformin group, compared with those in the insulin group. Babies in the metformin group weighed, on average, 108 grams less at birth. It appeared, though, their weight ‘caught up’ in infancy, showing a higher body mass index by mid-childhood, compared with those in the insulin group.

Some experts believe that more research needs to be done in this area, to understand any potential long term associated health risks.

Despite the many positive findings from randomized controlled trials, it’s always important you discuss your options with your care providers, as metformin might not be appropriate for everyone and there are other alternatives.

Babies born to mothers with diabetes in pregnancy will usually be monitored carefully immediately after birth and in the early postnatal period. Babies whose mothers are diabetic are at increased risk of hypoglycemia, due to the relative ‘drop’ in high blood glucose levels from the mother after birth.

For this reason, they might need their blood glucose levels monitoring after birth; skin to skin and an early feed might also be encouraged – even more so for these babies.

Related reading: Benefits Of Skin To Skin Breastfeeding.

Metformin and PCOS (polycystic ovary syndrome)

Metformin is sometimes used ‘off label’, to treat women with polycystic ovary syndrome (also referred to as polycystic ovarian syndrome). Polycystic ovary syndrome is a condition that affects how the ovaries work. The condition can affect fertility, due to abnormal hormone levels leading to irregular, or no periods, problems with ovulation, and abnormal insulin levels.

Many women with polycystic ovary syndrome are resistant to the action of insulin in the body; therefore, they produce greater levels of insulin to compensate. This also contributes to abnormal levels of certain hormones, such as testosterone.

Impaired glucose tolerance and abnormal hormone levels can lead to fertility problems; some practitioners will prescribe metformin, therefore, to help control insulin resistance.

Metformin treatment helps to lower blood glucose levels by altering the way the body processes insulin. This can improve hormone levels and ovulation and regulate periods, increasing the likelihood of conceiving.

Being overweight or obese also increases the amount of insulin the body produces. Losing weight prior to pregnancy, therefore, could help with insulin sensitivity and fertility and also improve maternal and fetal outcomes in pregnancy.

To learn more, read our article PCOS – What is PCOS? (PolyCystic Ovarian Syndrome)

Can I get pregnant while taking metformin?

Metformin is used to treat type 2 diabetes and GDM; it can also help to prevent it in those who are at risk of developing it.

If you are taking metformin prior to getting pregnant, you will normally be advised to continue to take it throughout pregnancy. It’s still important, though, to let your health care providers know if you become pregnant, as your dose might need to be altered, and you might need additional input from specialists throughout your pregnancy.

The risks of type 2 diabetes in pregnancy are greater, compared with those of gestational diabetes mellitus, and the evidence regarding the use of metformin versus insulin is limited. However, it’s thought that metformin should be continued, during pregnancy, for those already established on it, with the knowledge that insulin treatment might need to be added. Although, research has shown that if insulin is required in addition to metformin, smaller doses are likely to be needed to maintain glucose levels, compared with the use of insulin alone.

Pregnant women with PCOS are at higher risk of developing gestational diabetes, gestational hypertension and of going into preterm labor; therefore, metformin therapy could help reduce the chances of these things happening.

Is it safe to take metformin while pregnant?

There are no known risks in using metformin during pregnancy. Metformin is used to treat pregnant women with PCOS, type 2 diabetes or gestational diabetes, and is approved as the first choice of treatment, over insulin.

Studies have compared the use of metformin, as opposed to insulin, in the treatment of gestational diabetes mellitus, and metformin is generally considered a safe and effective option in the short term management of GDM. Some studies have associated exposure to metformin, compared with exposure to insulin, with lower maternal weight gain, and lower risk of neonatal hypoglycemia (low blood sugar) and macrosomia (larger than average baby for gestational age).

There is no evidence to suggest that pregnancy exposure to metformin increases incidences of malformations or miscarriages.

Another benefit of metformin over insulin is that it’s generally considered to have a more acceptable means of administration. Insulin is given via an injection into the body or, in some cases, through a pump, whereas metformin administration is given in the form of tablets or a liquid. Therefore, metformin is more convenient and cost effective.

Metformin might be appropriate to treat pregnant women with milder forms of gestational diabetes. However, for some, metformin might not be enough to maintain the desired effect on glucose levels, so they could require insulin in addition to metformin therapy.

Metformin treatment can be used safely alongside insulin.

The latest National Institute of Clinical Excellence (NICE) guidelines state, ”Offer metformin to women with gestational diabetes if blood glucose targets are not met using changes in diet and exercise within 1–2 weeks. Offer insulin instead of metformin to women with gestational diabetes if metformin is contraindicated or unacceptable to the woman’.

What does metformin do for my body while pregnant?

Metformin helps the body improve its sensitivity to insulin. This means that the organs and tissues become more sensitive to the insulin produced by the body, and so the body uses it more effectively.

Metformin use reduces the liver’s release of extra glucose and slows down the absorption of carbohydrate that is consumed in the diet.

This results in lowered blood glucose levels, without them dropping too low. It is uncommon for metformin to cause dangerously low blood glucose levels, causing something known as hypoglycemia, or a ‘hypo’.

Hypos can happen if you are taking metformin alongside insulin or other diabetic medication, if you accidentally take too much, if you skip meals or during fasting.

Signs of a hypo are:

Feeling hungry
Shaking or trembling
Confusion
Sweating
Poor concentration
Collapse.

Seek immediate medical attention if you experience any of the above.

Metformin side effects

Commonly reported side effects of metformin are:

Vomiting or nausea
Indigestion
Diarrhoea
Stomach ache
Loss of/reduced appetite
Metallic taste in mouth.

These common side effects can happen to more than 1 in 100 people taking metformin.

Unlike other diabetes medications, metformin is not thought to cause weight gain; therefore, gestational weight gain could be lowered for metformin treated women.

As gastro-intestinal side effects are common, it’s helpful to take your metformin medication with food, or soon after eating, to reduce the chances of unpleasant side effects.

You will normally be started on a low dose, which will be gradually increased until the desired effect on glucose levels is achieved. This helps your body acclimatise to the medication, whilst personalizing a dose that is right for you.

B12 deficiency can be a side effect of taking metformin, although it’s more common with higher doses or if metformin is taken over a prolonged period of time.

Speak to your doctor if you experience any of the following signs or symptoms of B12 deficiency, including:

Fatigue
Muscle weakness
Mouth ulcers or sore red tongue
Visual problems
Pale or yellow skin.

If you are experiencing side effects that concern you, speak to your diabetic team. A different form of metformin might be suitable for you with fewer side effects, or you might require a different form of therapy.

In summary

Polycystic ovary syndrome, type 2 and gestation diabetes mellitus can all have an impact on maternal and infant outcomes; therefore, getting the right support, advice and treatment (if needed), is vital for a healthy pregnancy and birth.

If you’ve been diagnosed with type 2 diabetes or PCOS, prior to pregnancy, speak to your care team about how you can help prepare your body for pregnancy. This will give you and your baby the best chance at a successful and healthy pregnancy.

Once pregnant, or if you develop gestational diabetes during pregnancy, you might be offered additional support and/or treatment from a specialist diabetic team. Keeping yourself as active and healthy as you can, through diet, exercise and healthy lifestyle habits, will help you and your baby thrive in pregnancy.