Insulin changes during pregnancy, for women with type 1 diabetes
Insulin requirements tend to change constantly throughout pregnancy as different hormones take effect and your baby grows. You need to be prepared to adjust your insulin doses on a regular basis. It is not uncommon to need to make adjustments to your doses or pump settings at least every few days.
If you are not sure how to adjust your insulin doses or pump settings, ask your diabetes in pregnancy team for advice. Adjusting insulin doses in pregnancy is more challenging than usual, so make sure you know how to get in touch with your diabetes team and be prepared to contact them more often.
Early pregnancy changes
Many women find it extremely challenging to keep blood glucose levels in the target range in the early stage of pregnancy with so many hormonal and physical changes occurring. For around the first six to eight weeks of pregnancy your blood glucose levels may be more unstable.
Following these early pregnancy changes to your blood glucose levels, you may find that your insulin requirements are lower until the end of the first trimester. You are likely to need to adjust your insulin doses or pump delivery at this time to reduce the risk of hypos occurring, especially severe ones.
It is also important to be aware that during pregnancy, sometimes hypos can occur without much (or any) warning. Preventing a hypo is better than treating one. Try not to miss any meals or snacks and check your blood glucose levels regularly.
While most women find that they need lower insulin doses in early pregnancy, this is not the case for everyone. Your diabetes in pregnancy team can help you with advice on individual insulin dose adjustments.
Mid to late pregnancy changes
From the second trimester of pregnancy, especially after 18 weeks your insulin requirements will usually start to rise. By around 30 weeks you may need up to two or three times as much insulin as you did before pregnancy. Hormones made by the placenta interfere with the way your insulin normally works, so as the pregnancy hormones rise, so does your need for insulin.
In the second half of pregnancy, you are likely to need more mealtime, (rapid-acting/bolus insulin), compared with the long-acting (basal) insulin. Insulin requirements tend to continue to rise until about 34 to 36 weeks, when they may plateau or start to fall a little. If you notice your insulin requirements fall significantly and rapidly in late pregnancy, promptly contact your diabetes in pregnancy team for advice.
Changes after the birth
Once your baby is born and your placenta is delivered, your insulin requirements will fall dramatically. The mother’s insulin requirements tend to be very low for the first few days after the baby is born and then gradually increases. However, if you had Celestone injections before the birth, your insulin requirements will probably fall less.
Your target blood glucose levels should be reviewed after the birth, and frequent blood glucose monitoring is recommended. Target blood glucose targets will be higher than your pregnancy targets. This helps reduce the risk of hypos while you are establishing breastfeeding, and a new routine with your baby. The Australasian Diabetes in Pregnancy Society (ADIPS) recommends keeping blood glucose levels in the 5–10mmol/L range at this stage.
In the first few weeks, you will usually still need less insulin than you did before the pregnancy. If you are breastfeeding, once your milk comes in your insulin requirements may decrease again. Your endocrinologist or credentialled diabetes educator will help you re-adjust your insulin doses after birth. In the later stages of pregnancy or before you go home from hospital, discuss with your diabetes health professionals the best way of contacting them. It can be challenging managing your diabetes in the early weeks/months with a new baby.