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How Type 1 Diabetes Affects Twin Pregnancies

Increasing need for insulin in mothers carrying multiple babies as compared to mothers carrying single.

According to the American College of Obstetricians and Gynecologists, carrying multiple babies has a higher risk of pregnancy complications, such as gestational diabetes, preeclampsia, effects on fetal growth and even effects on risk of postpartum depression. The purpose of this study is to determine whether pregnant women carrying multiples have a higher risk of developing diabetes, therefore requiring a higher insulin level than pregnant women carrying single babies.

This was a retrospective study to gather details from 15 women carrying twins compared to a 108 prospective study of women carrying singles and with both groups having type 1 diabetes. Tests like blood pressure, HbA1c, and insulin dose were recorded at weeks 8, 14, 21, 27 and 33. Patients self-monitored their Plasma Glucose (SMPG) and values assessed at their clinic visits. Preprandial, postprandial and prebedtime SMPG of 72-108mg/dL (4-6mmol/L), 72-144mg/ dL (4-8mmol/L) and 108-144mg/ dL (6-8mmol/L) respectively were maintained. For their second trimester, an HbA1c of <5.6% is suggested. Statistical analysis done included the X2 test or the Fisher’s exact test. The average rise in total insulin needed was based on up to 33 weeks since most multiples do not make it to full term.

Insulin requirements for a twin pregnancy had an increase until 8 weeks, then a small decline to week 14; it then changed again by having a drastic increase until week 27. The value sustained until the 33rd week. This insulin requirement was comparable to a  single pregnancy until week 14. However, between weeks 14 and 27 there is a much higher insulin requirement in twin pregnancies than in single pregnancies with values of 3.0 IU (0.9-4.9) as against 1.5 IU (-1.5 to 5.9) and a P value of 0.008, which is considered statistically significant. The average rise in insulin requirement was therefore greater than in a single pregnancy with values of 103% (36-257%) as against 71% (-20 to 276%) with 45% higher than that of single births and a P value of 0.07.

In summary, this study demonstrates that women with type 1 diabetes and carrying twins require more insulin between 14 and 27 weeks as compared to women having single babies. The insulin value, however, remained constant from 27 to 33 weeks, and this could be due to restricted growth in fetal development, which normally occurs in multiple pregnancies. In pregnant women carrying twins with no type 1 diabetes, there was no fetal growth restriction. For single pregnancies, their insulin requirement still increased from 27 weeks. Type 1 patients carrying single birth had their insulin requirement increased from week 27 to 33. The total insulin dose was 45% greater with twin pregnancies as compared to single birth women with type 1 diabetes. Pregnant women with type 1 diabetes therefore required less insulin in their third trimester of their pregnancy. The weakness of this study is that only 15 cases of twin pregnancy data was collected even though the time period was long.

A different study was coordinated by the Rosie Hospital in Cambridge, U.K, to determine whether fetal overgrowth precedes the diagnosis of gestational diabetes mellitus (GDM) and to weigh the connection between fetal overgrowth, GDM, and maternal obesity. A prospective cohort study of nulliparous singleton pregnant women were recruited and blood samples were drawn. Continuous blood samples were drawn at 20, 28, and 36 weeks, as well as their ultrasound scans taken. Using the ellipse function on a machine, the fetal head circumference (HC) and abdominal circumference (AC) were measured between 20-28 weeks. The BMI of the mother is calculated with a maternal obesity being ≥30kg/m2. The women were screened for GDM by either doing the 50-g glucose challenge test (GCT), which may be followed by the 75-g OGTT if GCT was > 139mg/dL (7.7mmol/L). Women diagnosed as having GDM were provided a postpartum 2-h, 75-g fasting OGTT to prevent any ongoing glycemic imbalance. Statistical analysis like Wilcoxon rank sum test and Pearson X2 test were used.

Of the 4,069 women, 171 had GDM at ≥ 28 weeks. For the fetal biometry connected to GDM, there was no significant difference at week 20 until 28 weeks. GDM and maternal obesity had a 2.0-fold risk of AC > 90th and a 1.5-2.0–fold risk of HC to AC ratio < 10th percentile.

In conclusion, it was found that excessive fetal growth preceded clinical diagnosis of GDM. Also at 28 weeks the risks of AC>90th and HC-AC ratio< 10th percentile were doubled.

Practice Pearls:

  • Women with type 1 diabetes and carrying twins require more insulin between the 14 and 27 weeks compared to women having single babies.
  • Pregnant women with type 1 diabetes therefore required less insulin in their third trimester of pregnancy.
  • The excessive fetal growth preceded clinical diagnosis of GDM and at 28 weeks the risks of AC>90th and HC to ac ratio< 10th percentile were doubled.
  • This study proposed that screening prior to 28 weeks may be one way of improving both short- and long-term outcomes of pregnancies complicated by GDM.


Callesen, Nicoline F. et al. “Insulin Requirements in Type 1 Diabetic Pregnancy: Do Twin Pregnant Women Require Twice as Much Insulin as Singleton Pregnant Women?” Diabetes Care 35.6 (2012): 1246–1248. PMC. Web. 7 June 2016.

Hartling L, Dryden DM, Guthrie A, et al “Screening and diagnosing gestational diabetes mellitus.” Evid Rep Technol Assess (Full Rep) 2012:1-327

Moyer VA; U.S. Preventive Services Task Force. “Screening for gestational diabetes mellitus;: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med 2014; 160: 414-420

Sovio, Ulla et al. “Accelerated Fetal Growth Prior to Diagnosis of Gestational Diabetes Mellitus: A prospective Cohort Study of Nulliparous Women”. Diabetes Care 39 (2016); Web. 7 June