BACKGROUND AND PURPOSE:

• Prepregnancy diabetes is associated with morbidity and adverse pregnancy outcomes, especially if glycemic control is suboptimal
• However, it is unclear if improving glycemic control from preconception to mid early pregnancy and midpregnancy can reduce adverse outcomes
• Davidson et al. (JAMA Network Open, 2020) assessed whether improved glycemic control from preconception to the first half of pregnancy is associated with a lower risk of adverse outcomes

METHODS:

• Population-based cohort study
• Population
  • Births among women with prepregnancy diabetes
• Exposures
  • Net decrease in HbA1c from preconception to early pregnancy and midpregnancy
• Study design
  • HbA1C was measured (1) within 90 days preconception and (2) from conception through 21 weeks
  • Adjustments were made for maternal age at conception, preconception HbA1C and hemoglobin concentration, and gestational age at HbA1C measurement
• Primary outcome
  • Congenital anomaly from birth to age 1 year
• Secondary outcomes
  • Neonatal: Preterm birth <37 weeks, stillbirth or neonatal death  
  • Severe maternal morbidity (SMM) that is a composite of approximately 40 perinatal indicators or maternal death

RESULTS:

• 3459 births
  • Mean maternal age 32.6 years
• Overall, the mean HbA1c decreased from prepregnancy to early-to-midpregnancy
  • Preconception: 7.2%
  • Early to midpregnancy: 6.4%

Congenital Anomalies

• Overall
  • Incidence: 14.4%
  • Adjusted relative risk (aRR) 0.94 (95% CI, 0.89 to 0.98) per 0.5% net decrease in HbA1c
• Cardiac anomalies
  • aRR 1.09 (95% CI, 1.06-1.13) per 0.5% increase in preconception HbA1
• Benefit of net decrease in HbA1C
  • 2.0% absolute net decrease in HbA1C: 12.0% absolute risk for congenital anomaly (95% CI, 14.0% to 17.4%)
  • 0% net decrease in HbA1C: 15.6% absolute risk for congenital anomaly (95% CI, 10.4% to 13.8%)
  • Benefit most apparent in women with preconception HbA1C ≥6.4%

Preterm Birth

• Improved glycemic control was associated with a reduced risk for preterm birth
  • aRR 0.89 (95% CI, 0.86 to 0.91)
• Preterm birth (<37 weeks)
  • aRR 1.08 (95% CI, 1.06-1.09) for each 0.5% higher preconception HbA1C  
• Extreme preterm birth (<32 weeks)
  • aRR (1.09; 95% CI, 1.04-1.14) for each 0.5% higher preconception HbA1C
• Perinatal mortality
  • aRR (1.16; 95% CI, 1.11-1.22) for each 0.5% higher preconception HbA1C

Maternal Outcomes

• SMM or death from 21 weeks up to 42 days postpartum
  • Incidence: 5.5%
  • aRR 0.90 (95% CI, 0.84 to 0.96) for each 0.5% net decrease in HbA1C

CONCLUSION:

• Women with prepregnancy diabetes who obtain better glycemic control between preconception and early-to-midpregnancy (prior to 21 weeks) may reduce their risk of adverse neonatal and maternal outcomes including preterm birth
• The rate of SMM was higher than expected as was the probability of a congenital anomaly, suggesting the patients in this current study may have been especially predisposed to adverse events
• The authors point out that with half of all pregnancies unplanned in Canada and the United States, improved periconception glucose control may be beneficial especially in women with preconception HbA1C above 6.4%   

Learn More – Primary Sources:

Association of Improved Periconception Hemoglobin A1c With Pregnancy Outcomes in Women With Diabetes

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