General anaesthesia and oxytocin significantly associated with PPH in twin pregnancies

A retrospective cohort study of twin pregnancies in Hong Kong has identified general anaesthesia (GA) and use of oxytocin as significant risk factors for all postpartum haemorrhage (PPH; ≥500 mL). The study also shows that GA, in vitro fertilization (IVF), antepartum haemorrhage, placental abruption, and placenta praevia (PP) are significantly associated with major PPH (>1,000 mL), while IVF, PP, and obesity are significant risk factors for severe PPH (>1,500 mL).

The incidence of twin pregnancies is on the rise in developed countries due to increasing maternal age and use of assisted reproductive procedures. [Twin Res Hum Genet 2007;10:626-632; Semin Perinatol 2012;36:156-161] While PPH is more common in twin than in singleton pregnancies, few studies have investigated specific risk factors for PPH in twin pregnancies, because twin pregnancy itself is considered a risk factor for PPH due to substantial distension of the uterus, which leads to uterine atony after delivery. [Am J Obstet Gynecol 2013;209:449.e1-e7; Obstet Gynecol 2000;95:899-904]

Present study included all women with twin pregnancies who delivered at >24 weeks of gestation in a single tertiary obstetric training unit in Hong Kong between 2009 and 2018. Of 47,076 deliveries during the study period, 680 were twin pregnancies, which were included in the final analysis. [Hong Kong Med J 2023;29:295-300]

The overall incidence of all PPH in this cohort of twin pregnancies was 27.8 percent, with minor PPH accounting for 20.1 percent of cases, major but not severe PPH occurring in 4.4 percent of cases, and severe PPH recorded in 3.2 percent of cases. “In our [centre’s] database, the overall incidence of all PPH [27.8 percent vs 5.7 percent], as well as incidence of major [including severe] PPH [7.6 percent vs 0.86 percent] and severe PPH [3.2 percent vs 0.44 percent], were all significantly [p<0.001] higher in twin pregnancies than in singleton pregnancies during the study period,” noted the researchers.

Most instances (77.8 percent) of PPH in twin pregnancies were caused by uterine atony. Other causes were PP or placenta accreta (18.0 percent) and genital tract trauma (4.2 percent). “Although most instances of PPH in twin pregnancies were caused by uterine atony, 86.4 percent of women with uterine atony had only minor PPH. In contrast, 82.4 percent of women with PP had major PPH,” highlighted the researchers.

Nulliparity and use of oxytocin were significantly associated with all PPH, but not major or severe PPH. Although significant in univariate analysis, nulliparity did not remain significant in logistic regression analysis.

Univariate analysis showed that IVF, maternal obesity, antepartum haemorrhage, PP, placental abruption, Caesarean delivery, GA, and intrapartum pyrexia were significantly associated with various types of PPH. Logistic regression analysis revealed that GA and use of oxytocin were significant risk factors for all PPH, while GA, IVF, antepartum haemorrhage, placental abruption, and PP were significant risk factors for major PPH. Same analysis found IVF, PP, and obesity to be significant risk factors for severe PPH.

“Women with twin pregnancies who are obese, conceived by IVF, or have PP should deliver in obstetric units with readily available blood product transfusions, which have a multidisciplinary team of experienced obstetricians, anaesthesiologists, interventional radiologists, and haematologists who can promptly manage severe PPH,” advised the researchers.