Univariate analysis of characteristics of women, labour and delivery associated with UPPBL, clinical PPH, and controls.

<p>Univariate analysis of characteristics of women, labour and delivery associated with UPPBL, clinical PPH, and controls.</p

Undiagnosed abnormal postpartum blood loss: Incidence and risk factors

<div><p>Background</p><p>We aimed to evaluate the incidence of undiagnosed abnormal postpartum blood loss (UPPBL) after vaginal delivery, identify the risk factors and compare them to those of postpartum haemorrhage (PPH).</p><p>Method</p><p>The study population included women who participated in a randomized controlled trial of women with singleton low-risk pregnancy who delivered vaginally after 35 weeks’ gestation (n = 3917). Clinical PPH was defined as postpartum blood loss ≥ 500 mL measured by using a collector bag and UPPBL was defined by a peripartum change in haemoglobin ≥ 2 g/dL in the absence of clinical PPH. Risk factors were assessed by multivariate multinomial logistic regression.</p><p>Results</p><p>The incidence of UPPBL and PPH was 11.2% and 11.0% of vaginal deliveries, respectively. The median peripartum change in Hb level was comparable between UPPBL and PPH groups (2.5 g/dL interquartile range [2.2–3.0] and 2.4 g/dL IQR [1.5–3.3]). Risk factors specifically associated with UPPBL were Asian geographical origin (adjusted OR [aOR] 2.3, 95% confidence interval [CI] 1.2–4.2; p = 0.009), previous caesarean section (aOR 3.4, 2.1–5.5; p<0.001) and episiotomy (aOR 2.6, 1.8–3.6; p<0.001). Risk factors for both UPPBL and PPH were primiparity, long duration of labour, instrumental delivery and retained placenta.</p><p>Conclusion</p><p>Undiagnosed abnormal postpartum blood loss is frequent among women giving birth vaginally and has specific risk factors. The clinical importance of this entity needs further confirmation, and the benefit of systematic or targeted prevention strategies needs to be assessed.</p></div

Multivariate analysis^a of risk factors for UPPBL and PPH (n = 3917).

<p>Multivariate analysis<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0190845#t004fn001" target="_blank">^a</a> of risk factors for UPPBL and PPH (n = 3917).</p

Characteristics of the study population (n = 3917).

<p>Characteristics of the study population (n = 3917).</p

Prepartum, postpartum and median peripartum change in haemoglobin (Hb) level, number of women with postpartum anemia and blood loss in women with undiagnosed abnormal postpartum blood loss (UPPBL), postpartum haemorrhage (PPH) and controls.

<p>Prepartum, postpartum and median peripartum change in haemoglobin (Hb) level, number of women with postpartum anemia and blood loss in women with undiagnosed abnormal postpartum blood loss (UPPBL), postpartum haemorrhage (PPH) and controls.</p

Association between induction of labor and risk of PPH and severe PPH in low-risk women, multivariable analyses^* (N = 4477 PPH, 1125 severe PPH and 1744 controls).

*<p>6 multileveled logistic regression models with random intercept.</p>**<p>3 models adjusted for maternal age, parity, epidural analgesia, duration of active phase of labor, mode of delivery, episiotomy/perineal tears, prophylactic oxytocin after birth and birth weight.</p>***<p>3 models adjusted for maternal age, parity, epidural analgesia, duration of active phase of labor, mode of delivery, episiotomy/perineal tears, prophylactic oxytocin after birth, birth weight and % of PPH with no documented Hb delta (level 2 covariable)</p

Characteristics of women, labor and delivery in women with PPH, severe PPH and in control women.

*<p>% of non-missing values</p>‡<p>% of all women in the group</p>**<p>chi2 test comparing PPH cases and controls</p>***<p>chi2 test comparing severe PPH cases and controls</p

Association between induction of labor and risk of PPH and severe PPH among low-risk primiparas, multivariable analyses^*.

*<p>6 multileveled logistic regression models with random intercept.</p>**<p>3 models adjusted for maternal age, parity, epidural analgesia, duration of active phase of labor, mode of delivery, episiotomy/perineal tears, prophylactic oxytocin after birth and birth weight.</p>***<p>3 models adjusted for maternal age, parity, epidural analgesia, duration of active phase of labor, mode of delivery, episiotomy/perineal tears, prophylactic oxytocin after birth, birth weight and % of PPH with no documented Hb delta (level 2 covariable)</p

Selection of the study population.

<p>Selection of the study population.</p

Risk factors of PPH after vaginal delivery.

a<p>Simple logistic regression.</p>b<p>Multivariable logistic regression including all listed variables.</p