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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 dose at least once a week.

If you are not sure how to adjust your insulin doses, 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 maintain optimal blood glucose levels 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 decrease until the end of the first trimester. You may need to adjust your insulin doses at this time to reduce the risk of severe hypos occurring, sometimes 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.

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 as much as two or three times your daily pre-pregnancy insulin dose. This is because the hormones made by the placenta interfere with the way your insulin normally works—as the pregnancy hormones rise, so does your need for insulin. At this stage, you are likely to need more mealtime, rapid-acting insulin, compared with the long-acting/basal insulin.

Insulin requirements tend to continue to rise until about 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, this can be a sign of problems with the pregnancy—contact your specialist for advice immediately.

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 increase.

Your target blood glucose levels should be reviewed after delivery. These blood glucose targets will be higher than your pregnancy targets to reduce the risk of hypos while you are establishing breastfeeding, and a new routine with your baby.

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 diabetes educator will help you re-adjust your insulin doses after delivery.

Discuss the best way of contacting your diabetes health professionals once you go home from hospital, as it can be challenging managing your diabetes in the early weeks with a new baby.