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Abstract

The prevalence of diabetes among women of reproductive age is increasing, in part due to the increase in type 2 diabetes. Despite available pharmacologic treatments such as oral medication and insulin, efficacy and safety data for use during pregnancy are limited, and changes in insulin requirements throughout pregnancy further complicate management. Insulin is the preferred pharmacologic treatment option for pregnant women with gestational and preexisting diabetes. Deciding which type of insulin to use during pregnancy depends on several factors. The pharmacodynamic profile of each insulin type, dosing, delivery systems, monitoring, and the quality of efficacy and safety data are all important considerations. Evidence from randomized controlled studies is preferred over data from other types of studies of pregnant individuals. Furthermore, exciting advances in delivery systems and monitoring technology may improve medication-taking behavior and/or lead to better pregnancy outcomes for women with diabetes. In this review, we examine the management of both gestational and preexisting diabetes, including trimester-specific glucose targets, data from randomized controlled trials for each insulin type, and advances in technology.

Keywords

pregnancy review type 1 diabetes type 2 diabetes gestational diabetes

Introduction

The worldwide prevalence of diabetes among pregnant women is more than 19%, and the prevalence of preexisting diabetes (type 1 [T1D], type 2 [T2D]) has doubled over the past 3 decades.^1,2 Notably, there has been an upward trend in the incidence of T2D among women of reproductive age, with the most marked changes observed in North America, where the incidence has increased by 3.5% annually from 1990 to 2021.³ This increase coincides with an increase in the prevalence of obesity and may also be due in part to a rise in the age at which women are conceiving.^4,5

Uncontrolled diabetes during pregnancy can lead to adverse outcomes for both mother and infant. For women with uncontrolled gestational diabetes mellitus (GDM), cesarean and preterm delivery are more likely, and infants born to women with GDM have an increased risk of respiratory distress and an increased requirement for admission to the neonatal intensive care unit (NICU).⁶ Additionally, the lifetime maternal risk of developing T2D is 8- to 10-fold greater among women with previous GDM compared with women with normoglycemic pregnancies.^7,8 Adverse pregnancy outcomes associated with preexisting diabetes include increased rates of congenital malformation, miscarriage, fetal demise, hypertensive pregnancy disorders, and cesarean delivery compared with women without diabetes.⁹ Preterm birth (<37 weeks), large for gestational age (LGA) infant, neonatal hypoglycemia, and NICU admission are also more likely to occur with preexisting diabetes than without diabetes.¹⁰ A recent study also found a 61% higher chance of intellectual disability among offspring born to women with preexisting diabetes compared with offspring born to women with no diabetes.¹¹ Among those with T1D, there is a 6-fold greater risk of pre-eclampsia than women without T1D¹² and preterm birth (<37 weeks), LGA infant, neonatal hypoglycemia, and NICU admission are more likely in T1D than T2D and GDM pregnancies.¹⁰

Retinopathy, a leading cause of blindness, has been shown to develop and progress more rapidly and to a greater severity during pregnancy among women with T1D and T2D who have preexisting retinopathy.¹³ Risk factors for progression to advanced stages of retinopathy include longer duration of diabetes and high glycated hemoglobin (HbA1c) values.¹⁴ Diabetic ketoacidosis (DKA), which is associated with fetal loss and maternofetal morbidity, can also occur in as many as 10% of pregnancies.^15,16 Risk of DKA in pregnancy is increased due to the natural rise in insulin-antagonizing hormones and accelerated starvation, characterized by lipolysis and ketogenesis.¹⁵

Despite available pharmacologic treatments for managing diabetes, such as oral medications, human insulin, and insulin analogs, treatment options during pregnancy are limited. Oral medications such as metformin and glyburide are often prescribed to women with T2D before pregnancy and are continued during pregnancy; however, these oral agents may not be effective at maintaining glycemic control. In a randomized controlled trial (RCT) of pregnant women with T2D comparing the efficacy of metformin with human insulin, more than 85% of patients taking metformin required the addition of insulin to maintain glycemic targets.¹⁷ Safety is also a concern because these medications cross the placenta to the fetus, and for glyburide, the risk of neonatal hypoglycemia is significantly increased in comparison to insulin.^18,19 Furthermore, the American Diabetes Association (ADA) recommends that oral agents not be used as first-line treatment for managing diabetes during pregnancy because of the risk of adverse outcomes.²⁰ Insulin remains the preferred pharmacologic agent in pregnancy because it does not cross the placenta²¹; however, insulin therapy has indirect effects via the regulation of maternal glucose.²² Despite advances in treatment and new delivery modes, insulin therapy is still nuanced by the need for continuous dosing modification to meet the demands of increasing insulin resistance as pregnancy progresses. In this review, we discuss each type of insulin used to manage diabetes during pregnancy, focusing on evidence from RCTs, noting where RCT data are lacking.

Methodology

Using PubMed, we conducted a comprehensive literature review of guidelines, expert consensus, and systematic reviews of insulin use during pregnancy published through November 2025. The search included all insulin types (rapid-acting/human, analogs, long-acting, and concentrated) across each diabetes type (GDM and preexisting diabetes [T1D and T2D]) with a focus on RCTs. The authors reviewed and selected the most relevant/key RCTs to include. Additionally, package labels/United States Prescribing Information for each Food and Drug Administration (FDA)-approved insulin were reviewed and cross-checked for RCT data in pregnant women.

Discussion

Glucose targets and recommendations

The consensus on glucose levels for T1D, T2D, and GDM treated with insulin is as follows: 70–95 mg/dL (3.9–5.3 mmol/L) for fasting glucose, 110–140 mg/dL (6.1–7.8 mmol/L) for 1-h postprandial glucose, and 100–120 mg/dL (5.6–6.7 mmol/L) for 2-h postprandial glucose.²⁰ Levels should not decrease below 60 mg/dL (3.33 mmol/L) during the night.¹⁶ A recent consensus statement provides recommendations for continuous glucose monitoring (CGM) targets during pregnancy, including a pregnancy-specific time-in-range (TIRp) target for T1D of >70% (glucose range of 63–140 mg/dL [3.5–7.8 mmol/L]).²³ The consensus statement suggests a target TIRp of >80% for T2D and >90% for GDM, acknowledging that the evidence for these targets is limited and clinical judgment should be used.²³

There is also evidence that glucose control early in the first trimester, when embryogenesis occurs, may reduce the risk of fetal anomalies.¹⁶ Insulin is recommended by the American College of Obstetricians and Gynecologists (ACOG) and the ADA for the management of preexisting diabetes during pregnancy, and because one in two women with T2D will require insulin for glycemic control, transitioning to insulin before or during pregnancy is recommended.^16,20 Insulin is also the preferred agent for managing GDM.²⁰ The need for insulin in women with GDM can depend on several factors, such as maternal age, obesity, previous history of GDM, family history of diabetes, altered fasting plasma glucose (FPG) at oral glucose tolerance test (OGTT), and hypothyroidism.²⁴ Achieving and maintaining glycemic control during pregnancy can be challenging due to changes in insulin sensitivity throughout pregnancy, delayed insulin absorption, and delayed gastric emptying.²⁵ Furthermore, women with GDM, T1D, and T2D have different insulin needs. Insulin sensitivity and dosing are discussed in the “Insulin Dosing” section of this review.

Insulin use during pregnancy: Data from RCTs

While there is a paucity of data available to help health care professionals select an insulin type, insulins investigated in RCTs are preferred over those investigated in cohort studies or case reports.²⁰ To this end, and to narrow the focus of our review, we review data from RCTs for each insulin type. Additional data (outside of RCTs) and perspectives are provided in the “Author Insights” boxes.

Human insulin

Human insulin has been a treatment option since the early 1980s. Short-acting human insulins, including Humulin R and Novolin R, generally take effect within 30 min, reach their peak in 2–3 h, and last up to 6 h (Table 1). Intermediate-acting human insulins, such as neutral protamine Hagedorn (NPH), take longer to begin working (up to 4 h) and can take up to 12 h to peak, but have a longer duration (up to 18 h) than short-acting human insulins. Compared with analogs, human insulins have demonstrated similar efficacy for treating diabetes during pregnancy.²⁶ However, some evidence suggests that human insulins are less effective than insulin analogs in reducing postprandial glycemia.^27,28 In an RCT comparing perinatal outcomes among women with T1D, offspring of those treated with NPH had significantly lower gestational age at delivery than those treated with detemir; however, safety outcomes were similar between groups.²⁹ A composite pregnancy outcome was attained in 63% of those treated with detemir compared with 66% of those treated with NPH (difference was not statistically significant).²⁹ An RCT comparing regular human insulin plus insulin analog detemir with regular human insulin plus NPH showed that after 1 week of treatment, FPG was significantly lower in the detemir group than the NPH group (P < 0.05), and the time to achieve the target blood glucose level was significantly shorter among women with GDM (Table 2; Supplementary Table S1).³¹ Maternal and fetal outcomes between groups were comparable, but there was a significantly higher incidence of hypoglycemia in the NPH group.

Table 1.

Overview of Pharmacologic Characteristics by Insulin Type^a

Insulin type	Onset	Peak	Duration
Human
Regular (short/intermediate)	30 min	2–3 h	3–6 h
NPH (intermediate-acting)	2–4 h	4–12 h	12–18 h
Analogs
Rapid-acting
Aspart	15 min	1–2 h	3–4 h
Lispro U-100	15 min	1–2 h	3–4 h
Glulisine	15 min	1–2 h	3–4 h
Long-acting
Glargine U-100	1 h	6–8 h	16–24 h
Detemir U-100	1–2 h	Minimal	14–24 h
Degludec U-100 (ultra-long)	1–2 h	None	30–>42 h
Concentrated
Lispro U-200 (rapid)	15 min	30–90 min	4–5 h
Degludec U-200	1–4 h	No significant peak	∼42 h
Glargine U-300 (ultra-long)	6 h	No significant peak	≥24 h
Insulin U-500	30 min to 1 h	2–4 h	∼21h

Information derived from current literature and each drug manufacturer’s prescribing information.

NPH, neutral protamine Hagedorn.

Table 2.

Key Randomized Controlled Trial Efficacy Data in Pregnancy by Insulin Type

Type	Study population	Comparator and primary outcome	Primary outcome results/Conclusion
Human
Regular	GDM	• Versus glyburide • Glycemic index control (FPG and postprandial)	No statistically significant differences between glyburide and regular human insulin³⁰
NPH	GDM and pre-GDM	• Plus regular human insulin versus detemir + regular human insulin • Preprandial and postprandial blood glucose concentrations after 1 week	Significantly lower FPG in the detemir group than in the NPH group³¹
Analogs
Rapid-acting
Aspart	GDM	• Versus human insulin • Degree of neonatal macrosomia	Frequency of neonatal macrosomia was numerically lower (not statistically significant) with aspart versus human insulin and was noninferior, with comparable fetal outcomes³²
	T1D	• Versus human insulin • Fetal and perinatal outcomes	Comparable fetal outcomes between aspart and human insulin, with a tendency toward fewer fetal losses and preterm deliveries with aspart³³
	T1D	• Versus human insulin • Hypoglycemia	Lower rates of hypoglycemia with aspart + NPH versus regular human insulin²⁷
	T1D	• Versus human insulin • Severe hypoglycemia	Aspart given at preconception may have a smaller risk of severe hypoglycemia versus aspart given at the beginning of pregnancy³⁴
Lispro	GDM	• Versus human insulin versus aspart • Glucose control/pregnancy outcomes	Lispro and aspart had lower 1-h postprandial maternal glucose control and newborn anthropometric measures versus human insulin³⁵
Lispro	T1D	• Versus regular insulin • Glucose control	No clear difference in glucose control (lispro had significantly lower blood glucose after breakfast versus regular insulin)³⁶
Glulisine		No RCT data in pregnant women	—
Long-acting
Glargine		No RCT data in pregnant women	—
Detemir	T1D	• Versus NPH • Glycemic control (HbA1c at 36 gestational weeks)	Detemir was noninferior to NPH for glycemic control³⁷
	T2D	• Versus NPH • Risk for adverse neonatal outcome	Detemir had lower rates of adverse neonatal outcomes versus NPH, driven by improvement in respiratory outcomes and NICU admission³⁸
	GDM/T2D	• Versus NPH • Overall blood glucose	Detemir was noninferior to NPH for glucose control³⁹
Degludec	T1D	• Versus detemir • Noninferiority assessed via last planned HbA1c before delivery	Degludec was noninferior to detemir⁴⁰
Concentrated insulins		No RCT data in pregnant women	—

FPG, fasting plasma glucose; GDM, gestational diabetes mellitus; HbA1c, glycated hemoglobin; NICU, neonatal intensive care unit; NPH, neutral protamine Hagedorn; RCT, randomized controlled trial; T1D, type 1 diabetes; T2D, type 2 diabetes.

Insulin analogs

Analog insulins were developed to better simulate normal human physiology and provide a more favorable pharmacokinetic and pharmacodynamic profile.

Rapid-acting analogs

Rapid-acting insulin analogs, which include insulin aspart, lispro, and glulisine, generally begin working within 15 min of injection, peak in 1–2 h, and last for 2–4 h (Table 1). Rapid-acting analogs are typically preferred over regular human insulin because they have a more rapid onset and offset of action, allowing administration to occur closer to mealtime (5–15 min before a meal or immediately after, rather than 30 min before).^41–43

For the rapid-acting analog glulisine, RCT data in pregnant women are lacking. The effectiveness of insulin aspart in managing diabetes during pregnancy has been investigated in two RCTs, each including more than 300 patients. Among pregnant women with GDM, aspart was shown to be noninferior (had comparable fetal outcomes) to human insulin.³² When aspart and human insulin were combined with NPH, aspart was associated with lower rates of maternal hypoglycemia compared with human insulin in an RCT among pregnant women with T1D.^27,33 Additionally, fetal and maternal outcomes were comparable between aspart and human insulin groups, and there was a trend toward fewer fetal losses and preterm deliveries in the aspart group.^27,33

A study of 96 women with GDM found that lispro was associated with better postprandial maternal glucose control and newborn anthropometric measures than human insulin.³⁵ Similarly, a study among 49 women with GDM showed 1-h postprandial values with lispro to be significantly lower than values among those receiving regular insulin.⁴⁴ Two-h postprandial values were normal and similar between groups, as were anthropometric measures, except for a significantly higher rate of infants with a cranial–thoracic circumference ratio in the 10th–25th percentile in the regular insulin group compared with the lispro group.⁴⁴ In a small RCT among 33 pregnant women with T1D, those treated with lispro had significantly lower blood glucose after breakfast than those treated with regular insulin; however, pregnancy complications and fetal outcomes were similar between groups.³⁶

Different formulations of rapid-acting analogs, which include excipients to increase absorption speed and stability, are also available and may provide additional benefit. For example, the ultrarapid-acting insulins lispro and aspart can be injected at the beginning of or within 20 min after starting a meal.^45,46 Additionally, in an open-label RCT among women with T1D and T2D (CopenFast trial), similar safety, HbA1c, and fetal growth outcomes were observed between those treated with fast-acting aspart compared with those treated with insulin aspart.⁴⁷

Long-acting analogs

Analogs such as glargine U-100, degludec U-100, and detemir U-100 reach the bloodstream a few h after administration and are categorized as long acting because they have a duration of action of approximately 24 h, except for degludec, which lasts ∼42 h (Table 1). Although no RCTs have been conducted in pregnant women treated with glargine, meta-analyses comparing glargine with NPH have shown that efficacy and safety outcomes (perinatal and neonatal) are similar.^48,49

For insulin detemir, a neutral, soluble human insulin analog, an assessment of maternal efficacy and safety outcomes among women with T1D showed lower FPG and noninferior HbA1c in late pregnancy (>36 weeks) with detemir versus NPH and comparable hypoglycemia rates.³⁷ Gestational age at delivery for offspring was significantly greater in the detemir group than in the NPH group.²⁹ Detemir is as well tolerated as NPH and has a similar incidence of adverse events, including fetal and perinatal mortality.²⁹ Among women with T2D, detemir has generally been associated with lower rates of adverse neonatal and maternal outcomes versus NPH; however, those treated with detemir had a higher probability of requiring increased intravenous glucose and having offspring with higher birthweight at delivery compared with NPH.³⁸ In an RCT among those with preexisting diabetes or GDM, detemir was found to be noninferior to NPH (no differences in perinatal and maternal outcomes); however, those in the NPH group experienced more hypoglycemia events.³⁹ Although detemir was discontinued in the United States in 2024,⁵⁰ degludec, an ultra-long-acting analog, was shown to be noninferior to detemir for use during pregnancy.⁴⁰

Degludec, considered an ultra-long-acting analog due to its duration of ∼42 h (Table 1), was evaluated in more than 200 pregnant women with T1D in the randomized controlled EXPECT study.^40,51 Results, which are included in the degludec package insert,⁵¹ showed degludec plus mealtime aspart to be noninferior to detemir plus mealtime aspart based on the primary outcome of last planned mean HbA1c before delivery (6.2% for degludec and 6.3% for detemir).⁴⁰ No additional safety issues were observed with degludec versus detemir.

Concentrated insulin

As pregnancy progresses and insulin resistance increases, a larger insulin dose may be needed to achieve glycemic control. This requires multiple injections and can lead to discomfort, pain, and scarring. One management approach to lowering the injection volume and reducing the number of insulin injections is to use concentrated insulin formulations as an alternative to traditional 100 units/mL (U-100) insulin. Currently available concentrated insulin formulations include regular insulin U-500, lispro U-200, degludec U-200, and glargine U-300, each with a distinct pharmacologic profile (Table 1). Despite some similarities with U-100 formulations, concentrated insulins may have different pharmacologic profiles and instructions for use (e.g., dosing), and they are only available in pens.

Although there are currently no RCT data assessing the use of concentrated insulin during pregnancy, a case study of a pregnant woman with T2D reported the use of U-500 regular insulin administered via continuous subcutaneous insulin infusion for basal insulin coverage, combined with U-100 prandial insulin pen injections.⁵² Results showed that the U-500 regimen achieved pregnancy glycemic targets and reduced basal insulin requirements by more than one-third.

Insulin dosing

Changes in insulin requirements are trimester-specific and vary depending on the type of diabetes. Insulin sensitivity in the first trimester is higher than insulin sensitivity prepregnancy and during the second and third trimesters, which can increase the risk of hypoglycemia, particularly when nausea and vomiting are present.^53–55 Around week 16 of pregnancy, insulin resistance begins to increase due to a progressive rise in the production of human placental lactogen, estrogen, and prolactin,¹⁶ and total daily insulin requirements increase by approximately 5% weekly through week 36.⁵³ After week 36, insulin requirements become flat (level off) or sometimes decrease. In contrast to T2D, women with T1D generally have higher insulin requirements during the first 2 trimesters and require greater increases in insulin per trimester.⁵⁶

Guidance for insulin dosing during pregnancy varies. The ADA provides general guidance to increase total daily insulin dosing by 5% each week from week 16 to week 36 to account for increased insulin resistance.²⁰ The ACOG notes increasing insulin requirements as pregnancy progresses from 0.7 to 0.8 units/kg/day, 0.8 to 1 units/kg/day, and 0.9 to 1.2 units/kg/day for the first, second, and third trimesters, respectively.^16,55 Although the Endocrine Society does not explicitly provide insulin dosing recommendations, it notes that adding metformin to insulin regimens reduces the insulin requirement (1.1 ± 1.0 versus 1.5 ± 1.1 units/kg; P < 0.0001).⁹

Although there may be some benefits in adding metformin to the standard insulin regimen, such as lowering the insulin dose required for pregnant women with T2D,⁵⁷ the Endocrine Society and the European Society of Endocrinology recommend against adding metformin for those with T2D already taking insulin.⁹ This recommendation is based on evidence showing that the benefits of reducing the rate of having an LGA infant did not outweigh the potential increased risk for adverse outcomes for offspring.⁹

Insulin dosing titration generally occurs at regular clinic follow-up appointments (in-person and telephone/virtual visits) every 1–3 weeks and sometimes as frequently as—one to two times per week during times of rapid shifts in insulin responsiveness. Although dosage adjustment depends on the degree and type of hyperglycemia (fasting and/or postprandial), generally an increase in each specific insulin dose is made at each visit. Patient-centered dosing strategies have recently been investigated, including the use of a model based on patient-specific disease progression characteristics and dose response. One such model was used to optimize dosing in women with GDM and resulted in less drug being used and better glycemic control compared with original dosing regimens; however, RCT data are needed to confirm these results.⁵⁸ As patients may need to switch to a different insulin, dose conversion is an important consideration. Broadly, conversion from regular insulin to short-acting insulin analogs occurs at a 1:1 conversion rate (i.e., no change in insulin dose is required). Conversion from glargine or detemir to degludec requires approximately a 20% reduction in dose,^59,60 likely due to degludec’s optimal pharmacodynamic profile, greater efficacy, and longer duration of action.

Additional considerations for those with T2D

Patients with T2D often take other diabetes medications that affect insulin use and dosing. Patients who are referred to specialists are frequently on oral medications, as there may be reluctance among some health care professionals to prescribe injectables. Despite guidelines recommending insulin as the first-line treatment in pregnancy, the rate of metformin use is rising.⁶¹ Guidelines do not recommend adding metformin for patients with T2D already on insulin due to the risk of maternal-to-fetal transfer (fetal levels are as high as maternal levels).⁹ Patients with T2D are often already taking several medications for comorbid conditions or weight management (e.g., glucagon-like peptide-1 receptor agonists [GLP-1 RAs], sodium–glucose cotransporter 2 inhibitors, and metformin), so guidance on managing these patients is needed. For T2D, guidelines recommend discontinuing GLP-1 RAs before conception rather than during the first trimester.⁹ It is becoming increasingly common for patients with T1D to be taking GLP-1 RAs even though they are not currently FDA-approved for glycemic management in T1D; the same guidance should be followed as for T2D.

Future directions

Insulin delivery

Automated insulin delivery (AID) systems are among the many recent technological advances in diabetes treatment. AID consists of CGM connected to an insulin pump, which automates insulin delivery via a programmed algorithm. AID systems are considered hybrid closed-loop (HCL), requiring the user to enter carbohydrates or announce meals for mealtime boluses and use rapid-acting insulins. The use of AIDs during pregnancy can be beneficial; however, many AID system algorithms cannot customize glucose targets to account for trimester-specific changes in insulin resistance. In fact, many AID systems do not allow levels to be lowered to or below 100 mg/dL (5.5 mmol/L) or offer the necessary flexibility for rapidly increasing insulin requirements in the second and third trimesters.⁶²

As of November 2025, CamAPS® FX was the only AID system approved in the United States for use during pregnancy; it is a mobile application for managing glucose levels in people with T1D and features an adaptive algorithm and glucose targets as low as 80 mg/dL (4.4 mmol/L), which is optimal for the second and third trimesters.^63,64 Results from two crossover RCTs showed less hypoglycemia and improvement in overnight TIR with CamAPS FX compared with standard therapy.^65,66 Building on the results from the two RCTs, CamAPS was assessed in the automated insulin delivery amongst pregnant women with T1D (AiDAPT) trial, which showed a significant increase in TIR (10.5%) with the HCL system compared with standard insulin delivery with CGM.⁶⁷ The CRISTAL study compared the MiniMed 780G advanced HCL (AHCL) system with standard insulin therapy among pregnant women with T1D.¹³ There was no statistical difference in TIR, although the baseline TIR was higher than the TIR in the AiDAPT trial.^13,67 However, the MiniMed 780G system did provide some benefit in secondary outcomes, such as overnight TIR and reduced time below range. Based on these results, the MiniMed 780G was approved in Europe for use during pregnancy.⁶⁸ Notably, the lowest algorithm target is 100 mg/dL (5.5 mmol/L), and most users needed to enter supplemental carbohydrates to increase boluses.⁶⁹ The CIRCUIT study, which evaluated the efficacy of the Tandem t:slim × 2 insulin pump with Control-IQ (Control-IQ) for use in pregnant women with T1D, found that TIR (pregnancy-specific glucose range) was significantly greater with the closed-loop system than with standard of care (65.4% versus 50.3%).⁷⁰ Additional support for AID use among pregnant individuals with T1D is from a systematic review of 13 RCTs and observational studies, which showed AID systems to be associated with improved glycemic control compared with standard therapy. Results showed that among those using AID systems, time spent in normoglycemia was greater than with standard care, and glycemic variability was significantly lower.⁷¹ Another AID system, twiist, integrated with the adaptive Tidepool Loop algorithm, allows for a target range as low as 87 mg/dL (4.8 mmol/L) with premeal targets as low as 67 mg/dL (3.7 mmol/L). It has recently become available; however, data among pregnant individuals are lacking.^72,73

Inhaled insulin (Technosphere), a human insulin formulation approved for use in nonpregnant women, has an onset of 10–15 min, a peak of 35–55 min (depending on the dose), and a duration of 2 h.⁷⁴ Although RCTs are needed, data from a limited case series among women with T1D and T2D suggested that inhaled human insulin may be a safe alternative to rapid-acting analogs for routine meal coverage and correcting postprandial hyperglycemia.⁷⁵ Optimal dosing and efficacy during pregnancy are not yet known, but there is an ongoing trial (INHALE-GDM, NCT06535789) assessing inhaled insulin versus rapid-acting injections for postmeal glucose control in women with GDM.⁷⁶

Monitoring

Use of CGM among nonpregnant individuals has become increasingly common; however, there are mixed efficacy results in this population. Two RCTs among women with diabetes, including those with T2D, assessed the impact of CGM use on fetal growth and showed no significant differences in outcomes versus standard self-monitoring of blood glucose (SMBG).^77,78 Another RCT among pregnant women with T2D showed that 2 weeks of intermittently scanned CGM use improved TIR and reduced time above range compared with SMBG.⁷⁹ Findings from CONCEPTT, an RCT assessing CGM in pregnant women with T1D, showed real-time use of CGM (rtCGM) to be associated with lower HbA1c at 34 weeks compared with no CGM use; it was also associated with a significantly lower incidence of LGA fetus, reduction in neonatal hypoglycemia, shorter length of hospital stay, and fewer neonatal intensive care admissions.⁸⁰ An increasing volume of literature supports the use of CGM among individuals with GDM. The GRACE trial found that the use of rtCGM in women with GDM reduced LGA births, but was also associated with a slightly higher rate of small for gestational age births, although not statistically significant.⁸¹ In the Steady Sugar trial, although time spent in TIR was similar for the CGM and SMBG groups, the women with GDM using CGM had better outcomes, including lower rates of unscheduled cesarean sections, preterm deliveries, LGA births, and infant admissions to the NICU.⁸² In two RCTs among pregnant women with GDM, TIR was higher using rtCGM than conventional (capillary) blood glucose monitoring; however, it is unclear whether rtCGM use will translate to improved perinatal and neonatal outcomes.^83,84

More research is needed on CGM targets specific to T2D and GDM.^23,83 Early pregnancy glycemic patterns derived from CGM data have been shown to identify patterns associated with GDM as early as gestational week 13 and may provide an opportunity for earlier intervention.⁸⁵ The Hyperglycemia and Adverse Pregnancy Outcomes study was the first to suggest that the risk of worse maternal and neonatal delivery outcomes increases across the spectrum of maternal glucose values, even those not achieving formal diagnostic thresholds for GDM.⁸⁶ The Glucose Levels Across Maternity study utilized CGM in early pregnancy to detect maternal dysglycemia.⁸⁷ Both studies underscore that glucose levels in pregnant individuals fall below traditional diagnostic thresholds for GDM, but also that traditional testing may underestimate the incidence and degree of maternal glucose disorders.

Intrapartum and postpartum insulin management

For those with GDM, there is a greater risk of developing T2D compared with women without GDM, with higher rates of progression among women with high body mass index at follow-up.^7,8 Therefore, the ADA recommends that women with a recent history of GDM be screened for ongoing diabetes (75 g OGTT using nonpregnancy criteria) at 4–12 weeks postpartum.²⁰ Screening for T2D or prediabetes should occur every 1–3 years. OGTT is recommended over HbA1c because it is more sensitive for identifying glucose intolerance.²⁰ For most women with GDM, insulin may not be needed in the immediate postpartum period, as some oral therapies and lifestyle modification can reduce or delay the progression from GDM to T2D. Additionally, breastfeeding is recommended, as it has been shown to reduce the risk of developing T2D among those with GDM.

Prepregnancy insulin requirements for those with preexisting diabetes are substantially reduced after placental delivery, and return closer to prepregnancy levels 1–2 weeks postdelivery.⁸⁸ As such, women are generally advised to decrease insulin doses to 50%–80% of their prepregnancy dose immediately after delivery.⁸⁹ An RCT comparing intrapartum continuous subcutaneous insulin with IV insulin infusion among women with T1D showed no statistically significant difference in the primary outcome of neonatal hypoglycemia.⁹⁰ Efficacy of HCL systems in the postpartum period has also been demonstrated. Results from an analysis of two RCTs showed that, among women with T1D using HCLs, more than 80% of the time was spent in the target glucose range with minimal hypoglycemic events.⁹¹ As evidenced in the CRISTAL study, AHCL system use was associated with better glycemic control in the intrapartum and early postpartum periods compared with standard insulin therapy.⁹²

Conclusions

With the prevalence of diabetes increasing among those of reproductive age, pharmacologic treatment with insulin becomes increasingly important. Selecting the type of insulin for use during pregnancy depends on several factors, including trimester-specific insulin needs, insulin dosing and delivery options, and the varying onset and duration of action for each insulin. While more research is being conducted on insulin in pregnant individuals, data from RCTs should be given greater weight than data from other types of studies. The evolution of insulins with more efficient pharmacodynamics and physiological delivery systems, along with advances in monitoring technologies, may lead to improved glycemic control during pregnancy and better outcomes.

Authors’ Contributions

All authors contributed to the writing and critically edited each article version. All authors read and approved the final article.

Footnotes

Acknowledgments

Under the direction of the authors, medical writing and editorial support, as well as article submission assistance, were provided by Emily Seidman, MSc, and Rebecca Hahn, MPH, CMPP, of KJT Group, Inc. (Rochester, NY), funded by Novo Nordisk Inc. The authors authorized the submission of their article via a third party and approved all statements and declarations. Novo Nordisk Inc. also performed a medical accuracy review.

Author Disclosure Statement

D.I.: Speakers bureau and consultant for Novo Nordisk, Lilly, Medtronic, Sequel, Dexcom, Abbott, and Sanofi. A.L.C.: A.L.C.’s institution receives consulting and/or research support from Abbott Diabetes Care, Dexcom, Medtronic, Insulet, Tandem, MannKind, Novo Nordisk, Eli Lilly, Zealand, and Luna Diabetes. V.S.: No competing interests to disclose.

Funding Information

Funding for medical writing support for this article was provided by Novo Nordisk Inc. The authors had complete editorial control over the article’s contents. The authors did not receive financial support from Novo Nordisk Inc. related to this work. Novo Nordisk Inc. conducted a medical accuracy review of this article at the outline and final draft stages.

Supplemental Material

Abbreviations Used

References

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0.36 MB

Insulin and Pregnancy: A Narrative Review of Evidence and Perspectives

Abstract

Keywords

Introduction

Methodology

Discussion

Glucose targets and recommendations

Insulin use during pregnancy: Data from RCTs

Human insulin

Insulin analogs

Rapid-acting analogs

Long-acting analogs

Concentrated insulin

Insulin dosing

Additional considerations for those with T2D

Future directions

Insulin delivery

Monitoring

Intrapartum and postpartum insulin management

Conclusions

Authors’ Contributions

Footnotes

Acknowledgments

Author Disclosure Statement

Funding Information

Supplemental Material

Abbreviations Used

References

Supplementary Material