First-trimester fasting plasma glucose as a predictor of subsequent gestational diabetes mellitus and adverse fetomaternal outcomes: A systematic review and meta-analysis.

Background: The implication of intermediately elevated fasting plasma glucose (FPG) in the first trimester of pregnancy is uncertain.

Purpose: The primary outcome of the meta-analysis was to analyze if intermediately elevated first-trimester FPG could predict development of GDM at 24-28 weeks. The secondary outcomes were to determine if the commonly used FPG cut-offs 5.1 mmol/L (92 mg/dL), 5.6 mmol/L (100 mg/dL), and 6.1 mmol/L (110 mg/dL) correlated with adverse pregnancy events.

Data Sources: Databases were searched for articles published from 2010 onwards for studies examining the relationship between first-trimester FPG and adverse fetomaternal outcomes.

Study Selection: A total of sixteen studies involving 115,899 pregnancies satisfied the inclusion criteria.

Data Extraction And Data Synthesis: Women who developed GDM had a significantly higher first-trimester FPG than those who did not [MD 0.29 mmoL/l (5 mg/dL); 95 % CI: 0.21-0.38; P < 0.00001]. First-trimester FPG ≥5.1 mmol/L (92 mg/dL) predicted the development of GDM at 24-28 weeks [RR 3.93 (95 % CI: 2.67-5.77); P < 0.0000], pre-eclampsia [RR 1.55 (95%CI:1.14-2.12); P = 0.006], gestational hypertension [RR1.47 (95%CI:1.20-1.79); P = 0.0001], large-for-gestational-age (LGA) [RR 1.32 (95%CI:1.13-1.54); P = 0.0004], and macrosomia [RR1.29 (95%CI:1.15-1.44); P < 0.001]. However, at the above threshold, the rates of preterm delivery, lower-segment cesarean section (LSCS), small-for gestational age (SGA), and neonatal hypoglycemia were not significantly higher. First-trimester FPG ≥5.6 mmol/L (100 mg/dL) correlated with occurrence of macrosomia [RR1.47 (95 % CI:1.22-1.79); P < 0.0001], LGA [RR 1.43 (95%CI:1.24-1.65); P < 0.00001], and preterm delivery [RR1.51 (95%CI:1.15-1.98); P = 0.003], but not SGA and LSCS.

Limitations: Only one study reported outcomes at first-trimester FPG of 6.1 mmol/L (110 mg/dL), and hence was not analyzed.

Conclusion: The risk of development of GDM at 24-28 weeks increased linearly with higher first-trimester FPG. First trimester FPG cut-offs of 5.1 mmol/L (92 mg/dL) and 5.6 mmol/L (100 mg/dL) predicted several adverse pregnancy outcomes.