Risk factors for blood transfusion in Cesarean section: A systematic review and meta-analysis

The current study has been conducted to identify the risk factors associated with blood transfusion in women undergoing cesarean section (C-section). A detailed account of the risk factors associated withblood transfusion will ultimately prevent unnecessary crossmatching in hospitals , leading to the conservation of declining blood supplies and resources without subjugating the quality of care.We performed a rigorous literature search using electronic databases, including PubMed, Cochrane CENTRAL, and Embase, for studies evaluating the risk factors for blood transfusion in C-section published until March 31, 2021. The Newcastle-Ottawa Quality Assessment Scale was deployed to assess the methodologic quality of the included studies. Mean differences (MD) and odds ratios (OR) with 95% confidence intervals were calculated using Review Manager version 5.3.The search yielded 1563 records, 22 of which were eligible for inclusion, representing 426,094 women (10,959 in the transfused group and 415,135 in the non-transfused group). Participants in the transfused group had lower mean preoperative hematocrit (MD=-3.71 [-4.46, -2.96]; p<0.00001; I2=88%). Placenta previa (OR=9.54 [7.23, 12.59]; p<0.00001; I2=88%), placental abruption (OR=6.77 [5.25, 8.73]; p<0.00001; I2=72%), emergency C-section (OR=1.92 [1.42, 2.60]; p<0.0001; I2=75%), general anesthesia (OR=8.43 [7.90, 9.00]; p<0.00001; I2=72%), multiple gestations (OR=1.60 [1.24, 2.06]; p=0.0003; I2=85%), preterm labor (OR=3.34 [2.75, 4.06]; p<0.00001; I2=85%), prolonged labor (OR=1.68 [1.44, 1.96]; p<0.00001; I2=78%), unbooked cases (OR=2.42 [1.22, 4.80]; p=0.01; I2=80%), hypertensive disorders of pregnancy (OR=1.81 [1.72, 1.90]; p<0.00001; I2=71%), and fibroids (OR=2.32 [1.55, 3.47]; p<0.0001; I2=72%) were significantly higher in the transfused group compared to the non-transfused group. Chronic hypertension (OR=0.67 [0.29, 1.55]; p=0.36; I2=90%), maternal age (MD=0.09 [-0.27, 0.45]; p=0.62; I2=50%), maternal body mass index (MD=-0.14 [-0.81, 0.53]; p=0.67, I2=86%), diabetes (OR=0.93 [0.75, 1.15]; p=0.51; I2=52%), and malpresentation (OR=0.65 [0.38, 1.11]; p=0.13; I2=64%) were not significantly associated with an increased risk of blood transfusion in C-section in the two groups.Placenta previa, placental abruption, emergency C-section, booking status, multiple gestations, and preoperative hematocrit were the risk factors most significantly associated with blood transfusion, while a prior C-section did not increase the risk of transfusion.