Recurrent pregnancy loss is the miscarriage of two or three consecutive pregnancies in the first or early second trimester. Although approximately 20 percent of all recognized pregnancies result in miscarriage, less than 5 percent of women will experience two consecutive miscarriages, and only 1 percent experience three or more.
Miscarriages are caused by a variety of factors, including:
- Infection such as sexually transmitted infections, rubella, toxoplasmosis, ureaplasma, and mycoplasma.
- Genetic or chromosomal errors.
- Age: The miscarriage rate is about 13 percent for a woman in her 20s; rises to 20 to 25 percent for a woman in her late 30s; and is more than 50 percent after age 42.
- Exposure to environmental and workplace hazards such as high levels of radiation, solvents, insecticides, lead products, benzene, and mercury all seem to increase the chance of miscarriage.
- Hormonal problems such as not enough progesterone or polycystic ovarian syndrome (PCOS).
- Uterine abnormalities such as endometrial polyps, fibroids, adhesions, uterine septum, or incompetent cervix.
- Lifestyle factors such as smoking, drinking alcohol, or using illegal drugs.
- Blood incompatibility: Mother is Rh negative and baby is Rh positive.
- Immune system problems such as clotting disorders, lupus anticoagulant, lack of immune recognition of the fetus, and autoimmune diseases.
- Severe medical conditions such as kidney disease, heart disease, and thyroid problems
- Certain medications, such as the acne drug Accutane.
Many of the causes of miscarriage can be determined through testing and many can be corrected. However, in approximately 50 to 60 percent of women with pregnancy loss, no reason will be found. Recent research indicates that there is up to a 60 percent probability of having a successful pregnancy following one or two miscarriages. After three losses, the chance of having a successful pregnancy is approximately 40 percent.
Normally, the embryo implants in the uterine lining (endometrium). However, if the fallopian tube is blocked, damaged, or unable to transport the embryo to the uterus, the embryo may implant in the lining of the tube, resulting in an ectopic pregnancy. The fallopian tube cannot support the growing embryo. After several weeks the tube may rupture and bleed, resulting in a potentially serious situation. Ninety-five percent of ectopic pregnancies implant in the fallopian tube, but they can also occur in the cervix, ovary, or even within the abdomen.