Mode of birth in women with low-lying placenta: protocol for a prospective multicentre 1:3 matched case-control study in Italy (the MODEL-PLACENTA study).

INTRODUCTION: The term placenta praevia defines a placenta that lies over the internal os, whereas the term low-lying placenta identifies a placenta that is partially implanted in the lower uterine segment with the inferior placental edge located at 1-20 mm from the internal cervical os (internal-os-distance). The most appropriate mode of birth in women with low-lying placenta is still controversial, with the majority of them undergoing caesarean section. The current project aims to evaluate the rate of vaginal birth and caesarean section in labour due to bleeding by offering a trial of labour to all women with an internal-os-distance >5 mm as assessed by transvaginal sonography in the late third trimester. METHODS AND ANALYSIS: The MODEL-PLACENTA is a prospective, multicentre, 1:3 matched case-control study involving 17 Maternity Units across Lombardy and Emilia-Romagna regions, Italy. The study includes women with a placenta located in the lower uterine segment at the second trimester scan. Women with a normally located placenta will be enrolled as controls. A sample size of 30 women with an internal-os-distance >5 mm at the late third trimester scan is needed at each participating Unit. Since the incidence of low-lying placenta decreases from 2% in the second trimester to 0.4% at the end of pregnancy, 150 women should be recruited at each centre at the second trimester scan. A vaginal birth rate ≥60% in women with an internal-os-distance >5 mm will be considered appropriate to start routinely admitting to labour these women. ETHICS AND DISSEMINATION: Ethical approval for the study was given by the Brianza Ethics Committee (No 3157, 2019). Written informed consent will be obtained from study participants. Results will be disseminated by publication in peer-reviewed journals and presentation in international conferences. TRIAL REGISTRATION NUMBER: NCT04827433 (pre-results stage).

Antiphospholipid syndrome and pregnancy.

Since the 1960s, antiphospholipid antibodies have been known to be associated with repeated miscarriages and fetal losses. Other complications of pregnancy, such as preterm birth, with pre-eclampsia or severe placental insufficiency were also frequently reported and are included in the current classification criteria of the antiphospholipid syndrome. The titer, isotype or antigen specificity of the antibodies may be important in risk determination. The pathogenesis of pregnancy failures is not only linked to the thrombophilic effect of antiphospholipid antibodies but also to a direct effect of antibodies on trophoblast differentiation and invasion. The study of experimental animal models provided sound evidence of the pathogenic role of antiphospholipid antibodies both in lupus-prone and -naive mice. The classification of pregnant antiphospholipid syndrome patients as being at a 'high risk' has completely changed their prognosis due to obstetric monitoring and the application of effective therapy. In fact, despite the high rates of complications and preterm delivery, a successful outcome can now be achieved in a large majority of cases.