Pregnancy with twins is exciting but daunting. A twin pregnancy carries more risk for many things including preeclampsia, premature delivery and also gestational diabetes (GDM). The placenta is larger and there are more of the hormones that block how insulin works circulating in the mother. In addition the mother does not move around as much so there is less glucose being used by her muscles. This all generates a need for more insulin than a single baby pregnancy and hence GDM is more common. A woman with Type 1 or Type 2 diabetes who becomes pregnant with twins or triplets will need even more insulin than a routine pregnancy.
The approach to diagnosing GDM in a twin pregnancy is just the same as a singleton pregnancy but some would suggest screening earlier. Once diagnosed the management is similar with just a couple of wrinkles. As with all GDM the first focus should be on lifestyle and diet and many will succeed in controlling the glucose with these modifications alone. A problem can be that with twin pregnancy exercise can be more challenging and sometimes the person is put on bed rest both of which will put upward pressure on the glucose levels. In our clinic we play the cards as they fall and if the glucose cannot be controlled with diet alone then we offer therapy with insulin of the option of metformin explaining that in most countries including Canada it use during pregnancy is not formally approved by our regulatory Health Agency and hence its use is “off label”. Insulin is used if needed and sometimes large doses of insulin are required. These are the same factors that necessitate higher doses of insulin in a woman with Type 1 diabetes who is pregnant with twins.
A second wrinkle to bear in mind is that we treat GDM or pre-existing diabetes to prevent large babies that would be difficult to deliver and to reduce the risk of low sugars occurring in the baby after birth. In a twin pregnancy the size of an individual twin is less a concern in terms of delivery but the mom still has to carry them so she does not want the combined weights to come to too much. However in diabetes in pregnancy size can be deceptive. A baby from a diabetic intrauterine environment acts more like a premature infant with increased risk of lung problems, low calcium and jaundice. Since premature delivery (before 37 weeks is the most common risk for a twin pregnancy) we don’t want these newborns to be any more “premature” than they have to be and so want them exposed to as normal a glucose setting as possible. The same goes for the risk of neonatal hypoglycemia, a risk for a baby born early and for a baby born to a diabetic mom. Hence the need to keep the glucose well controlled in all diabetic pregnancies but especially twin or triplet pregnancies.
Twins take more insulin but then there is a double bundle of joy at the end of the rainbow.