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How does diabetes affect fertility and pregnancy?

Scientific support: PD Dr. Sandra Hummel

In most cases, women with type 1 or type 2 diabetes can get pregnant without problems. There are certain risks for mother and child. However, these risks can be significantly reduced with good planning and optimized care by diabetes specialists and specialist medical staff before and during pregnancy.

Women with diabetes who plan to have children should try to ensure their blood sugar levels are optimally managed before getting pregnancy. It is advisable to discuss preparatory measures with the treating physician. In some cases, it may be necessary to adjust the diabetes therapy. Examinations should also be carried to determine potential complications of diabetes.

Women with diabetes should attend all important examinations during pregnancy and pay special attention to their blood sugar levels. Hormone level fluctuations can hinder good management.

Women with type 1 or type 2 diabetes should plan to give birth at a perinatal center. These clinics are specialized in providing comprehensive medical care for mother and child.

A special case is pregnancy diabetes (gestational diabetes): In contrast to women who already had diabetes before getting pregnant, this disease develops during pregnancy. It usually disappears after giving birth. The associated blood sugar levels can often be brought under control using changes in diet.

Find out more about gestational diabetes here!

Normally, type 1 or type 2 diabetes has no negative effect on female fertility. If a woman with diabetes does experience difficulty getting pregnant, this often stems from other diseases, such as polycystic ovary syndrome (PCOS). This hormonal disorder disrupts the menstrual cycle and can lead to infertility.

If a woman with type 1 diabetes has a disrupted menstrual cycle, this usually returns to normal with the administration of intensified insulin therapy, comprised of short-acting and long-acting insulins.

When PCOS is accompanied by type 2 diabetes and obesity, weight loss can have a positive effect. The metabolism and menstrual cycle often normalize when the patient achieves a normal weight.

Infertility in men may be caused by undetected type 2 diabetes (prediabetes). Although still undetected, the blood sugar levels are already elevated. Nerves and blood vessels can be damaged in this phase, which  can affect potency. This can be combated with a healthy lifestyle, i.e., a balanced diet and sufficient physical activity.

Find out more about sexual dysfunction disorders here!

When planning to get pregnant, women with type 1 or type 2 diabetes should contact their diabetes specialist. The risk of fetal malformation rises if blood sugar levels are not optimally managed. For this reason, patients with diabetes should undergo specific testing of the following factors before getting pregnant:

  • Long-term sugar value (HbA1c)
  • Blood pressure
  • Blood lipid levels
  • Thyroid values, to rule out hypothyroidism or hyperthyroidism

The long-term blood sugar value should be below 7 percent (53 mmol/mol), or ideally below 6.5 percent (47.5 mmol/mol), 3 months before conception.

Women with diabetes should also be examined for signs of complications of diabetes before getting pregnant. These complications can affect organs such as the kidneys or the eyes. Existing cases of diabetic retinopathy become more pronounced during pregnancy, usually in the final trimester, and require treatment. Renal function should also be examined. It is also crucial that the blood sugar levels are optimally managed.

As with all women who wish to get pregnant, specialist associations recommend beginning with iodine and folic acid tablets before the pregnancy. Beginning at least 4 weeks before pregnancy and continuing until the end of the  12th week of pregnancy, women should take between 0.4 and 0.8 milligrams of folic acid (folate) per day.

At least 200 milligrams of an iodine prophylaxis supplement should be taken. Information on iodine-rich food and the use of iodized salt is recommended. The aim is to ensure the fetus receives enough iodine and to prevent thyroid-related complications.

Stopping smoking is essential for a good pregnancy and fetal health.

In cases of unwanted pregnancy, women with diabetes should seek medical advice as soon as possible.

Good to know:

It may be necessary to adjust diabetes therapy before pregnancy. For women with type 1 diabetes, this may mean that their doctor recommends switching to another type of insulin preparation. For women with type 2 diabetes, medical specialists recommend switching to insulin therapy.

As with all types of medication, care should be taken during pregnancy. For many types of blood sugar-reducing medications, there is little data available on their safety for the unborn child. For this reason, doctors recommend switching to insulin therapy (human insulin) before a planned pregnancy. Intensified insulin therapy or an insulin pump are used. In some cases, it is possible to get blood sugar levels under control through lifestyle changes, sufficient exercise and a healthy diet.

Finding the correct insulin dosage is not always easy. On top of this, any change in treatment can cause often uncertainty. For this reason, women with type 2 diabetes should take part in a course to learn how to inject and measure blood sugar levels correctly. There they will learn to use an insulin pen or insulin pump. The costs for the course are usually covered by the health insurance provider.

Find out more about insulin therapy here!

Women with type 1 or type 2 diabetes should aim for the following blood values during pregnancy:

  • Before meals: 65-95 mg/dl (3.6-5.3 mmol/l)
  • 1 hour after a meal: less than 140 mg/dl (less than 7.8 mmol/l)
  • 2 hours after a meal: less than 120 mg/dl (less than 6.7 mmol/l)
  • Before sleeping (approx. 10-11 pm) 90-120 mg/dl (5.0-6.7 mmol/l)
  • At night (approx. 2-4 am): Above 65 mg/dl (above 3.6 mmol/l)

It is recommended that pregnant women measure their blood sugar levels 6 times per day (1 hour before each meal, and 1 hour after). The average value should remain between 90 and 100 mg/dl (5.0 mmol/l and 6.1 mmol/l). A safe and reliable blood sugar measurement device should be used for blood sugar self-testing.

Blood sugar levels and insulin requirements change during pregnancy up until delivery due to the pregnancy hormones. During the 1st trimester, the amount of insulin required falls. During this period, the expectant mother must inject less insulin to prevent low blood sugar levels. The insulin requirements increase rapidly during the 2nd trimester and then dramatically fall again after giving birth.

During the 1st trimester, there is an increased risk of low blood sugar (hypoglycemia), especially during the night. To help estimate the risk of nocturnal low blood sugar, blood sugar levels can be tested at around 11 pm. If the reading is less than 110 mg/dl (less than 6.1 mmol/l), the risk increases. The diabetes specialist responsible for treatment must carefully adjust the insulin dosage. Pregnant women should definitely inform those close to them and their partner about what to do in the event of severely low blood sugar levels.

Ketoacidosis (acid buildup in the blood caused by lack of insulin) associated with pregnancy diabetes is an emergency situation. Expectant mothers discuss with their diabetes specialist at what blood sugar level they should begin testing acetone levels in the urine. In this case, rules regarding what the expectant mother can and can’t do are also put in place.

What examinations should the patient attend?

To ensure good management of type 1 or type 2 diabetes during pregnancy, the patient should attend the following check-ups, among others:

  • The German Maternity Guideline suggest 3 ultrasound examinations, which can be supplemented by additional examinations: Between the 8th to 12th, 11th to 14th and 28th to 32nd week of pregnancy From the 24th week of pregnancy, ultrasound examinations take place every 2 to 4 weeks. They should take place more often in the event of anomalies.
  • Between the 19th and 22nd  week of pregnancy, an anomaly scan of the fetal organs can be carried out.
  • The long-term blood sugar value (HbA1c) should be determined at intervals of between 4 and 6 weeks.
  • Ophthalmologic examinations to test for retinal damage (diabetic retinopathy) are recommended before falling pregnancy, in the early stages of pregnancy, and then every 3 months until giving birth. In the event of preexisting retinopathy or a newly developed condition, the ophthalmologist will schedule appointments based on the individual case.
  • After the 20th week of pregnancy, regular blood pressure testing should be carried out, or earlier depending on risk factors or signs of disease. The risk of high blood pressure is increased in patients with long-term diabetes. The protein excretion levels in the urine should also be monitored.
  • Thyroid panel testing should take place every 4 to 6 weeks.
  • Before giving birth, an estimation of the birth weight is recommended.

If the blood sugar levels are too high throughout pregnancy, the child can become too large and too heavy (birth weight exceeding 4500 grams). This can lead to complications during birth or cesarean section.

Diabetes-related complications, e.g., affecting the eyes, kidneys, or nerves, can become more pronounced during pregnancy and must be treated as early as possible.

During the later stages of pregnancy, expectant mothers can develop high blood pressure. In this case, self-testing of blood pressure can be carried out on a daily basis.

Pregnant women with diabetes are more likely to develop infections of the genital and urinary organs, which can lead to premature birth. For this reason, regular testing is recommended.

Preeclampsia, also known as gestosis or pregnancy poisoning, is especially serious. It is characterized by high blood pressure and increased excretion of protein via the urine (proteinuria). Preeclampsia, the most severe form of gestosis, is a very serious emergency situation that requires immediate hospital treatment.

Good to know:

Women with type 1 diabetes in particular can develop  low blood sugar levels during the 1st trimester, especially at night. Therefore, it may be necessary to temporarily change or adjust their course of treatment. Later in pregnancy, the blood sugar levels become more stable and the risk drops.

What are the dangers to the fetus?

The internal organs of the fetus develop during the 1st trimester of pregnancy. If the blood sugar levels are not optimally regulated before and during pregnancy, this can result in malformation of the heart, nervous system, and lungs in particular. Miscarriage and premature birth are also possible. The risk of premature birth (birth before the end of the 37th week of pregnancy) is on average 5 times higher for expectant mothers with diabetes. These risks can be significantly reduced thanks to targeted consultation, good metabolic management, and blood sugar self-testing.

Other typical complications include low blood sugar, jaundice (hyperbilirubinemia), or respiratory disorders.

Good to know:

Around 5 percent of children from mothers (or fathers) with type 1 diabetes will also develop diabetes mellitus, because the disease is partially genetically determined. When both parents or one parent and a sibling have type 1 diabetes, the risk increases further.

Expectant mothers are advised to give birth at a perinatal center (at least level 2). These clinics are specialized in high-risk pregnancies and premature births and have a pediatric clinic and neonatal intensive care unit. This enables newborns to quickly receive emergency care on site. For example, glucose can be administered intravenously in cases of newborns with low blood sugar levels.

The blood sugar levels of the mother at the start of childbirth should be between 80 and 130 mg/dl (4.4 to 7.2 mmol/l). Low blood sugar can lead to reduced contraction activity. The blood sugar levels should be monitored every 1 to 2 hours during childbirth and corrected if needed. Only short-acting insulins are administered during childbirth.

If labor begins so early that a substance to inhibit contractions is required, special attention must be paid to the blood sugar levels during this period. Certain types of medication can have a negative influence on metabolism.

Good to know:

All pregnant women with either type 1 or type 2 diabetes (using insulin therapy) should give birth at a perinatal center.

What happens after giving birth?

Mother and child require close monitoring after birth. The mother's insulin requirements fall rapidly after giving birth, increasing the risk of low blood sugar levels. It may be necessary to individually adjust the required amount of insulin. The dosage used before pregnancy can be used as a reference value. The blood sugar level should be tested every 4 to 6 hours.

When breastfeeding begins, the required amount of insulin can fall even further and adjustment is needed. Attention should be paid to ensuring sufficient carbohydrate intake during the day to prevent low blood sugar levels at night or after breastfeeding.

The children of mothers with diabetes should be breastfed and vaccinated like other children. The risk of children later developing obesity or type 2 diabetes is reduced by breastfeeding. However, in reality, mothers with diabetes tend to breastfeed more rarely and for a shorter period compared to non-diabetic mothers. Studies have shown that mothers with diabetes have more success breastfeeding when they participate in breastfeeding classes before giving birth.

Good to know:

Breastfeeding women with type 2 diabetes should not use blood sugar-reducing medication. If the blood sugar levels cannot be sufficiently brought under control with dietary adjustments, then insulin is used.

If possible, the newborn should be breastfed for the first time 30 minutes after birth and then every 2 to 3 hours. This has been proved to stabilize the blood sugar level of the newborn and prevent low blood sugar levels.

To prevent this most frequent complication affecting the children of diabetic mothers, the blood sugar level of the newborn is  regularly monitoring. The 1st blood sugar test takes place between 1 and 2 hours after birth. It is important to be aware of the possible signs of low blood sugar.

Find out more about low blood sugar levels here!


Boeri, L. et al.: Undiagnosed prediabetes is highly prevalent in primary infertile men - results from a cross-sectional study. In: BJU Int, 2019, 123: 1070-1077
Deutsche Diabetes Gesellschaft: Diabetes und Schwangerschaft. Evidenzbasierte Leitlinie der Deutschen Diabetes Gesellschaft. Langfassung. 2. Auflage. 2014
Gesellschaft für Neonatologie und Pädiatrische Intensivmedizin et al.: Betreuung von Neugeborenen diabetischer Mütter. Langfassung. 2. Auflage. 2017
Kleinwechter, H. et al.: Diabetes und Schwangerschaft. In: Diabetologie, 2017, 12: S233-S241
Kleinwechter, H. et al.: Diabetes und Schwangerschaft: Patientenversion der Leitlinie der Deutschen Diabetes Gesellschaft. 2008
As of: 03.11.2019