Factors Related to Blood Transfusions in Pregnant Women Undergoing Caesarean Sections: A 20-year Retrospective Study.

Background: The rising rates of caesarean section (CS) globally have been associated with an increase in maternal complications, including the need for blood transfusions. Maternal anaemia, uterine atony, and placenta-related disorders contribute significantly to haemorrhagic complications during CS. This study aimed to evaluate the factors associated with blood transfusions in pregnant women undergoing CS at Siriraj Hospital over a 20-year period. Methods: This large, retrospective study enrolled 1277 pregnant women who underwent CS and received blood transfusions at Siriraj Hospital between January 1999 and December 2019. Demographic data, baseline haematocrit, underlying diseases, indications for CS, and relevant neonatal details were retrieved from medical records. Statistical analyses were performed to identify factors associated with increased transfusion rates, with a focus on maternal anaemia, uterine atony, placenta previa, and placenta accreta spectrum. Results: Over the 20-year period, the rate of CS increased from 1.9% in 2002 to 48.5% in 2017. Concurrently, the need for blood transfusions also rose, with the highest transfusion rate recorded at 3.2% in 2019. The most common indications for transfusion were uterine atony (22.6%), placenta previa, and anaemia. Women with placenta accreta spectrum had a 6-fold higher likelihood of transfusion (aOR 6.530, 95% CI 4.056-10.510; P < 0.001), and those with uterine atony were 3.5 times (aOR 3.612, 95% CI 2.599-5.019; P < 0.001) more likely to require transfusions. Anaemic mothers also demonstrated a significantly higher risk for transfusion. Conclusion: Blood transfusion risk in CS is strongly linked to placenta accreta spectrum, uterine atony, and maternal anaemia. Early identification of high-risk pregnancies and optimization of antenatal care are essential for reducing transfusion needs and improving maternal outcomes. Clinical Trial Registration: Clinical trial number: TCTR20200505001 (Registered on 5 May 2020).