We did a comprehensive literature search on MEDLINE (from database inception to May, 2020). The date of our last search was May 14, 2020. We searched for existing systematic reviews and primary studies on risk factors for miscarriage (demographic, lifestyle, clinical, and environmental factors). A separate search was conducted for observational studies of obstetric, perinatal, and long-term health risks associated with miscarriage. Free text search terms and Medical Subject Headings terms for
SeriesMiscarriage matters: the epidemiological, physical, psychological, and economic costs of early pregnancy loss
Introduction
Miscarriage is often misunderstood by many women, men,1 and health-care providers, and misconceptions about miscarriage are widespread.1, 2, 3 For example, women might believe miscarriage is rare, that it could be caused by lifting heavy objects or previous contraceptive use, or that there are no effective treatments to prevent a miscarriage.3 Such misconceptions can be damaging, leaving women and their partners feeling at fault and not seeking treatment and support.1 Miscarriage can also lead to isolation, since many women might not tell their family, close friends, or even their partner about the loss of their pregnancy. Couples have voiced concerns over unsympathetic routine clinical care by health-care providers.4, 5, 6
Women and their partners who have had a miscarriage generally want to understand why the miscarriage occurred, what they can do to prevent miscarriage from happening again, what the chance is of a subsequent pregnancy resulting in a healthy baby, and how to deal with their grief surrounding their loss.3 Couples might be given diverse opinions by different health-care professionals, which can exacerbate their distress. There are also debates over definitions, causes, consequences, and costs of miscarriage. This paper is the first of three in this Series on miscarriage in which we present the current knowledge, recommendations, need for further research, and a call to action on priorities. We discuss the epidemiology of sporadic and recurrent miscarriage, and present a literature review of the risk factors and consequences of miscarriage on future obstetric and maternal psychological and long-term health. We also evaluate the economic cost of miscarriage through a review of the literature.
Section snippets
Definitions and terminology
The definition of miscarriage varies among countries and international organisations, affecting estimations of the risk and prevalence of miscarriage. Miscarriage is generally defined as the loss of an intrauterine pregnancy before viability; however, challenges exist over the diagnosis of pregnancy, and the definitions of what is unequivocally an intrauterine pregnancy and what is viability. The limits of viability can be defined by gestational age or by fetal weight. The gestational threshold
Risk of miscarriage
The risk of miscarriage depends on the defined upper gestational age or fetal weight limit, and whether the denominator is all pregnancies identified by serum or urinary β-hCG concentrations or only pregnancies diagnosed by ultrasonography. Inclusion of preclinical losses, defined as the loss of a pregnancy before diagnosis by ultrasonography, will increase the miscarriage rate. The development of highly sensitive β-hCG assays has allowed detection of very early pregnancies (from 22 days since
Recurrent miscarriage
Whether miscarriage should be defined as recurrent after two or more or three or more pregnancy losses is an ongoing controversy. There is also no consensus on whether recurrent miscarriage should be restricted to clinical losses only, or include both clinical and preclinical losses (appendix p 5). The definitions are further complicated by whether the previous pregnancy losses need to be consecutive or be interspersed with livebirths. The UK Royal College of Obstetricians and Gynaecologists
Embryonic chromosomal errors
Chromosomal abnormalities are found in 60% of miscarried tissue,36 but less than 1% of livebirths when prenatal diagnosis is not used.37 Among miscarriages, autosomal trisomy is the most frequent abnormality followed by monosomy X and triploidy.36 In addition, developmental abnormalities of embryos not seen in livebirths are found in miscarriages with normal chromosomes.38, 39
Endometrial defects
Endometrium transforms into decidua during implantation to accommodate the invading placenta.40 A defect in
Vaginal bleeding in early pregnancy and obstetric complications
Threatened miscarriage, defined as vaginal bleeding in early pregnancy (in the first 12 weeks of pregnancy), is among the most common reasons for women to seek medical care in early pregnancy.84 Clearly, events in early pregnancy have a substantial effect on pregnancy outcomes.85, 86, 87, 88 A systematic review of 14 studies (n=64 365) found that women who have had a threatened miscarriage have a higher risk of antepartum haemorrhage due to placenta previa (OR 1·62; 95% CI 1·19–2·22) or
Economic costs
We did a literature review with the goal of identifying and summarising evidence on the economic costs associated with miscarriage, the cost-effectiveness of prevention or management strategies, and preference-based outcomes associated with miscarriage, or its prevention or management derived with economic methods. A total of 30 articles were included: 15 articles reported costing studies, 12 articles reported economic evaluations, and three articles reported preference elicitation studies. Due
Discussion
Miscarriage is common, but its scale and effect are not fully understood by some women, family, care providers, policy makers, and health-care funders. There are multiple risk factors for miscarriage, most prominently female age and the number of previous losses. Some risk factors—eg, BMI, smoking, and alcohol—are modifiable. Environmental risk factors are an emerging concern. However, an association does not imply causation, and there is a need to better understand the nature, mechanisms, and
Search strategy and selection criteria
Declaration of interests
We declare no competing interests.
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