Assisted reproductive technology and prolonged third stage of labour: a multicentre study in Japan

What are the risk factors for a prolonged third stage of labour, closely related to postpartum haemorrhage, and what is the effect of assisted reproductive technology (ART) on the third stage of labour?

Clinical data of women who delivered vaginally at term at 12 primary maternity hospitals in Japan (2010-2018) (n = 25,336) were obtained; 1148 (4.5%) conceived through ART and 2246 (8.9%) through non-ART treatments. The risk of a prolonged third stage of labour (defined as ≥20 min) was evaluated by univariable and multivariable regression analyses. Adjusted odds ratios (aOR) of a prolonged third stage of labour were evaluated, stratified by the type of ART, with natural conception as a reference.

Multivariable analysis showed that pregnancy achieved through ART (aOR 4.38, 95% CI 3.12 to 6.15), history of spontaneous miscarriage (OR 1.40, 95% CI 1.06 to 1.84) and prolonged labour (OR 1.52, 95% CI 1.09 to 2.12) were identified as independent risk factors. Frozen embryo transfer (FET), FET in a hormone replacement cycle (HRC-FET) and blastocyst-stage embryo transfer were significantly associated with a prolonged third stage of labour (aOR 4.07, 95% CI 2.75 to 6.04, aOR 4.11, 95% CI 2.58 to 6.57 and aOR 2.13, 95% CI 1.15 to 3.95, respectively). No significant difference was observed in the duration of third stage of labour between natural conception and non-ART treatment (P = 0.61).

Pregnancy achieved through ART, particularly FET, HRC-FET and blastocyst-stage embryo transfer, was a significant risk factor for a prolonged third stage of labour.