Miscarriage can be caused by a number of factors including chromosome abnormalities, infections, immune disorder, anatomical abnormalities of the uterus, systemic illnesses, hormonal imbalance and substance abuse.
Effects of hormones on Miscarriage
Oestrogen and progesterone are two of the primary female sex hormones. During a normal menstrual cycle, they take turns driving the process of maturing and releasing an egg and preparing the uterus for possible pregnancy. Oestrogen rises in the first half of the cycle, peaks at ovulation and then falls in the second half as progesterone rises. Progesterone is released by the rupturing of the egg follicle during ovulation. Testosterone too is secreted in surges around the time of ovulation.
When oestrogen, progesterone and testosterone are doing their jobs, they work well together. How much or how little of each hormone is made at any one time relies on a complicated feedback system between the brain specifically the hypothalamus and the pituitary gland which releases LH (luteinizing hormone) and FSH (follicle stimulating hormone), the ovaries and the adrenal glands. Stress and diet affect these feedback mechanisms and so directly impact the hormonal balance.
At the time of ovulation, progesterone is responsible for an increase in body temperature, which lasts during most of the luteal phase. Low progesterone is a common cause of infertility in women. Progesterone is responsible for creating a proper environment for a fetus and its levels are supposed to increase upon fertilization of the egg. The hormone then supports the pregnancy by increasing tissue development in the uterus where the embryo will attach. If progesterone levels are low in the first several weeks of pregnancy, a miscarriage is likely to occur.
By about 8-9 weeks of pregnancy, the placenta usually takes over the production of progesterone.