Low-lying placenta a risk factor for postpartum bleeding

Women with an antepartum diagnosis of low-lying placenta are twice as likely as those with normal placentation to have postpartum haemorrhage (PPH), according to a systematic review and meta-analysis.

Researchers searched multiple online databases for studies involving women with singleton pregnancies and compared PPH and placenta accreta spectrum outcomes in relation to a diagnosis of low-lying placenta.

A total of 21 studies met the eligibility criteria and were included in the meta-analysis. The total population comprised 3,704 patients with low-lying placenta and 2,555 controls with normal placentation. Quality assessment was performed using the Newcastle–Ottawa Scale.

At any gestational age, low-lying placenta was associated with a twofold increased risk of PPH (risk ratio [RR], 2.10, 95 percent confidence interval [CI], 1.02–4.35; p=0.05; I2=0.0 percent) compared with non–low-lying placenta.

The incidence of PPH was 16 percent (95 percent CI, 10.3–24.1; I2=93.3 percent) among patients with low-lying placenta, when the distance of the placenta from the cervical os was 1–20 mm, compared with 5.8 percent (95 percent CI, 3.8–8.8; I2=79.9 percent) among those with non–low-lying placenta.

A high incidence of PPH persisted despite the resolution status of the low-lying placenta (resolved: 8 percent, 95 percent CI, 4.1–16.3; I2=85.0 percent; unresolved: 29.2 percent, 95 percent CI, 19.0–42.0; I2=70.5 percent).

Furthermore, PPH risk also remained elevated regardless of the distance of the placenta from the cervical os (low-lying placenta 1–10 mm: 16.6 percent, 95 percent CI, 9.2–28.3; I2=78.4 percent; low-lying placenta 11–20 mm: 17.5 percent, 95 percent CI, 8.8–31.7; I2=92.2 percent; RR, 0.97, 95 percent CI, 0.67–1.41; p=0.84, I2=0.0 percent).

Placenta accreta spectrum disorders affected 9 percent (95 percent CI, 4.7–16.8; I2=89.9 percent) of all low-lying placenta cases.