The relationship between falling insulin requirements and serial ultrasound measurements in women with preexisting diabetes: a prospective cohort study.INTRODUCTION
 A large fall in insulin requirements (FIR) in women with diabetes is associated with adverse clinical outcomes but previous studies have not examined its relation with serial ultrasound parameters.


 OBJECTIVE
 To determine whether FIR is associated with alteration in umbilical artery Doppler parameters and fetal growth restriction (FGR) in women with preexisting diabetes.


 Serial obstetric Doppler ultrasounds were conducted 2 weekly from 28 weeks gestation in women with Type 1 and Type 2 diabetes who were being treated with insulin.  Estimated fetal weight (EFW), head circumference:abdominal circumference (HC:AC) ratio and umbilical artery doppler parameters (SD ratio) and pulsatility index (PI) were measured.  Information on insulin dose was collected prospectively throughout pregnancy and women with FIR ≥ 15% were considered cases.  Linear mixed effect models were used to assess the association between FIR and ultrasound parameters.


 One hundred and forty two women were included in the study (type 1 diabetes n = 41, type 2 diabetes n = 101).  There was no significant difference in the change of S/D ratio or PI over the third trimester in cases with FIR ≥ 15%, compared to the rest of the cohort, before or after adjusting for type of diabetes.  Likewise there was no difference in EFW and HC:AC ratio with advancing gestation before or after adjusting for variables known to influence fetal growth.  CONCLUSIONS
 FIR ≥ 15% was not associated with changes in placental flow or FGR however larger studies are needed to evaluate this further.
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