Abstract
Recurrent pregnancy loss (RPL), defined as three or more consecutive miscarriages, is hypothesized to share some of the same pathogenic factors as placenta-associated disorders. It has been hypothesized that a defect implantation causes pregnancy loss, while a partially impaired implantation may lead to late pregnancy complications. The aim of this retrospective register-based cohort study was to study the association between RPL and such disorders including pre-eclampsia, stillbirth, small for gestational age (SGA) birth, preterm birth and placental abruption. Women registered with childbirth(s) in the Swedish Medical Birth Register (MFR) were included in the cohort. Pregnancies of women diagnosed with RPL (exposed) in the National Patient Register (NPR), were compared with pregnancies of women without RPL (unexposed/reference). Obstetrical outcomes, in the first pregnancy subsequent to the diagnosis of RPL (n = 4971), were compared with outcomes in reference-pregnancies (n = 57,410). Associations between RPL and placental dysfunctional disorders were estimated by odds ratios (AORs) adjusting for confounders, with logistic regression. RPL women had an increased risk for pre-eclampsia (AOR 1.45; 95% CI; 1.24–1.69), stillbirth <37 gestational weeks (GWs) (AOR 1.92; 95% CI; 1.22–3.02), SGA birth (AOR 1.97; 95% CI; 1.42–2.74), preterm birth (AOR 1.46; 95% CI; 1.20–1.77), and placental abruption <37 GWs (AOR 2.47; 95% CI; 1.62–3.76) compared with pregnancies by women without RPL. Women with RPL had an increased risk of pregnancy complications associated with placental dysfunction. This risk population is, therefore, in need of improved antenatal surveillance.
Highlights
Recurrent pregnancy loss (RPL) is defined as two [1,2] or, traditionally more strictly, three or more consecutive miscarriages occurring before the fetus reaches viability [3]
It has been hypothesized that a defect implantation causes pregnancy loss, while a partially impaired implantation may lead to late pregnancy complications [20] such as pre-eclampsia, stillbirth, intrauterine growth restriction (IUGR), preterm birth and placental abruption [19,21,22,23]
The National Board of Health and Welfare (NBHW) enabled to deliver a random selection of about 5% of all childbirths in Sweden in the study period, which resulted in the conducted unexposed group (n = 57,410 pregnancies) by women without RPL
Summary
Recurrent pregnancy loss (RPL) is defined as two [1,2] or, traditionally more strictly, three or more consecutive miscarriages occurring before the fetus reaches viability [3]. The later definition of three or more miscarriages is used in this study since this definition is used in Sweden where the study is conducted. Other societies, such as the German, Austrian and Swiss Society for Obstetrics and Gynecology as well as the British Royal College for obstetrics and gynecology, support this definition [3,4]. RPL is distressing for the affected couples. About 0.5–2.3% [5,6,7,8,9,10] of women trying to conceive suffer RPL. Insufficient placentation on an immunological basis has been suggested as an additional explanation in this heterogeneous group [11,15]
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