Study of the birthweight of parents experiencing unexplained recurrent miscarriages

Miscarriage matters: the epidemiological, physical, psychological, and economic costs of early pregnancy loss

Miscarriage is generally defined as the loss of a pregnancy before viability. An estimated 23 million miscarriages occur every year worldwide, translating to 44 pregnancy losses each minute. The pooled risk of miscarriage is 15·3% (95% CI 12·5-18·7%) of all recognised pregnancies. The population prevalence of women who have had one miscarriage is 10·8% (10·3-11·4%), two miscarriages is 1·9% (1·8-2·1%), and three or more miscarriages is 0·7% (0·5-0·8%). Risk factors for miscarriage include very young or older female age (younger than 20 years and older than 35 years), older male age (older than 40 years), very low or very high body-mass index, Black ethnicity, previous miscarriages, smoking, alcohol, stress, working night shifts, air pollution, and exposure to pesticides. The consequences of miscarriage are both physical, such as bleeding or infection, and psychological. Psychological consequences include increases in the risk of anxiety, depression, post-traumatic stress disorder, and suicide. Miscarriage, and especially recurrent miscarriage, is also a sentinel risk marker for obstetric complications, including preterm birth, fetal growth restriction, placental abruption, and stillbirth in future pregnancies, and a predictor of longer-term health problems, such as cardiovascular disease and venous thromboembolism. The costs of miscarriage affect individuals, health-care systems, and society. The short-term national economic cost of miscarriage is estimated to be £471 million per year in the UK. As recurrent miscarriage is a sentinel marker for various obstetric risks in future pregnancies, women should receive care in preconception and obstetric clinics specialising in patients at high risk. As psychological morbidity is common after pregnancy loss, effective screening instruments and treatment options for mental health consequences of miscarriage need to be available. We recommend that miscarriage data are gathered and reported to facilitate comparison of rates among countries, to accelerate research, and to improve patient care and policy development.

Recurrent miscarriage is a useful and valid clinical concept

Although epidemiological, clinical and biochemical risk factors are known for recurrent miscarriage (RM), the etiology is mainly unknown. Two main hypotheses dominate: that RM is mainly caused by aneuploid conceptions and other conception errors and that the recurrence rate is explained by the combination of chance and increased risk, or that maternal endocrinological, thrombophilic or immunological abnormalities play a main role in causing loss of euploid conceptions. Believers of the former hypothesis advocate that management of RM should be conservative and that the spontaneous prognosis is very favorable. Believers of the latter hypothesis think that treatments aimed at the woman may improve pregnancy outcome, but that testing of such treatments in randomized controlled trials is needed. In this article in favor of RM being a specific and useful clinical concept, arguments are advanced that a significant subset of RM patients exhibit a poor spontaneous prognosis and should be offered relevant investigations, close surveillance during pregnancy, and treatment, preferably as part of randomized controlled trials.

Secondary recurrent miscarriage and H-Y immunity

BACKGROUND

Approximately half recurrent miscarriage (RM) cases remain unexplained after standard investigations. Secondary RM (SRM) is, in contrast to primary RM, preceded by a birth, which increases the transfer of fetal cells into the maternal circulation. Mothers of boys are often immunized against male-specific minor histocompatibility (H-Y) antigens, and H-Y immunity can cause graft-versus-host disease after stem-cell transplantation. We proposed the H-Y hypothesis that aberrant H-Y immunity is a causal factor for SRM.

METHODS

This is a critical review of the H-Y hypothesis based on own publications and papers identified by systematic PubMed and EMBASE searches.

RESULTS

SRM is more common after the birth of a boy and the subsequent live birth rate is reduced for SRM patients with a firstborn boy. The male:female ratio of children born prior and subsequent to SRM is 1.49 and 0.76 respectively. Maternal carriage of HLA-class II alleles presenting H-Y antigens to immune cells is associated with a reduced live birth rate and increased risk of obstetric complications in surviving pregnancies in SRM patients with a firstborn boy. In early pregnancy, both antibodies against HLA and H-Y antigens are increased in SRM patients compared with controls. Presence of these antibodies in early pregnancy is associated with a lower live birth rate and a low male:female ratio in subsequent live births, respectively. Births of boys are also associated with subsequent obstetric complications in the background population.

CONCLUSIONS

Epidemiological, immunogenetic and immunological studies support the hypothesis that aberrant maternal H-Y immune responses have a pathogenic role in SRM.

Families with a perinatal death: is there an association between the loss and the birthweight of surviving siblings?

Our objective was to study birthweight among surviving siblings in families with and without a perinatal loss, and to evaluate whether different causes of death were associated with the results. Data were for 1967-98 from the Norwegian Medical Birth Registry. Births were organised with the mother as the observation unit through the personal identification number, providing sibship files. We analysed 550 930 sibships with at least two singletons, 208 586 sibships with at least three singletons and 45 675 sibships with at least four singleton births. We compared mean birthweight and gestational age between infants in sibships with and without a perinatal loss, total losses and the different causes of death. Surviving siblings in families with a perinatal loss had significantly lower mean birthweights than their counterparts in unaffected families, after adjusting for gestational age, interpregnancy interval, time period and marital status. An exception was found when cause of death was a birth defect, when growth retardation among surviving siblings was not found on average. We conclude that families who have lost an infant because of a birth defect do not appear to have an increased risk of adverse birth outcome associated with growth restriction.

Obstetric and neonatal outcome in women with a history of recurrent miscarriage: a cohort study

Obstetric and neonatal outcomes of women who had a history of recurrent miscarriage were compared with a control population from 1 January 1992 to 30 June 1998. Amongst a total of 162 pregnancies which progressed beyond 24 weeks gestation in women with a history of recurrent miscarriage, there were four perinatal deaths and 16 babies were admitted to the special care baby unit. The rates of preterm delivery (13%), small-for-gestational-age (13%), perinatal loss (2.5%) and Caesarean section (36%) were significantly (P < 0.05) higher than those of the control group (3.9, 2.1, 1 and 16.7% respectively). The ratio of male to female babies was equal. There was no significant difference in the incidence of hypertension or diabetes between the two groups. Patients with recurrent miscarriage represent a population at high risk of obstetric problems and close surveillance in the antenatal period is therefore required.