Recurrent miscarriage is the spontaneous loss of three or more consecutive pregnancies in the first trimester, with the same biological father. It affects 1 to 2 percent of women, in one half of whom there is no identifiable cause.

• Overall, 75 percent of affected women will have a successful subsequent pregnancy, but this rate falls for older mothers and with increasing number of miscarriages.

• Antiphospholipid syndrome, with anti-cardiolipin or lupus anticoagulant antibodies, is present in 15 percent of women with recurrent first- and second-trimester miscarriage.

We do not know whether bed rest, early scanning, lifestyle adaptation (to stop smoking, reduce alcohol consumption, and lose weight), low-dose aspirin, human chorionic gonadotropin therapy, trophoblastic membrane infusion, or vitamin supplementation increases the likelihood of a successful pregnancy in women with unexplained, recurrent miscarriage.

We also do not know whether estrogen supplementation increases the live birthrate in women with unexplained recurrent miscarriage, but it may increase the miscarriage rate and cause fetal abnormalities.

• We do not know whether progesterone supplementation or corticosteroids reduce miscarriage rates compared with placebo in women with unexplained recurrent miscarriage.

Paternal white cell immunization and intravenous immune globulin treatment do not seem likely to improve live birth-rates compared with placebo in women with unexplained, recurrent miscarriage.

We do not know whether low-dose aspirin, alone or combined with heparin, can increase the live birthrate compared with placebo in women with antiphospholipid syndrome.

• Prednisolone plus aspirin may not increase live birthrates in women with antiphospholipid syndrome, and increases the risk of adverse effects compared with placebo.

Definition

Recurrent miscarriage is usually defined as three or more consecutive, spontaneous miscarriages occurring in the first trimester, with the same biological father. A successful birth may or may not follow. About one half of recurrent miscarriages are unexplained. Antiphospholipid syndrome is one of the known causes of first- and second-trimester recurrent miscarriage. Antiphospholipid syndrome is defined as the presence of anticardiolipin antibodies or lupus anticoagulant antibodies, in association with three or more consecutive fetal losses before 10 weeks of gestation, one or more unexplained intrauterine deaths after 10 weeks of gestation, or one or more premature births before 34 weeks of gestation due to severe preeclampsia or impaired fetal growth. This review covers unexplained recurrent miscarriages and first- and second-trimester recurrent miscarriages in women with antiphospholipid syndrome.

Incidence

In Western populations, recurrent miscarriage affects 1 to 2 percent of women of childbearing age, and about one half of these are unexplained. Antiphospholipid antibodies are present in 15 percent of women with recurrent miscarriage.

Etiology

Increasing maternal age and number of previous miscarriages increase the risk of further miscarriages. No separate risk factors for antiphospholipid syndrome are known.

Prognosis

On average, the live birthrate for women with unexplained recurrent miscarriage is 75 percent in a subsequent pregnancy, with a miscarriage rate of 20 percent up to nine weeks, and a 5 percent miscarriage rate after this period. However, prognosis varies depending on maternal age and number of previous miscarriages. The chance of a successful subsequent pregnancy after three previous unexplained miscarriages varies from about 54 percent in a 45-year-old woman to about 90 percent in a 20-year-old woman. A 30-year-old woman with two previous unexplained miscarriages has about an 84 percent chance of a successful subsequent pregnancy, whereas for a woman of the same age with five previous unexplained miscarriages, the success rate drops to about 71 percent.