Luteinising hormone (LH) controls the development and release of the egg from the ovary. Women who have high levels of this hormone in the first half of their menstrual cycle seem to have a greater risk of miscarriage. In addition, women with polycystic ovary syndrome (PCOS) have raised levels of LH.
Progesterone is the hormone which maintains the pregnancy during the first few weeks. After the egg has been released from the ovary, the ruptured follicle then develops into the corpus luteum, which produces progesterone. If the egg is not fertilised, after 14 days, the corpus luteum gets the message to continue producing progesterone. Without sufficient levels of progesterone, the pregnancy cannot continue, and that is why antiprogesterone drugs are now used to terminate an early pregnancy without the need for an operation.
Because of this obvious link between progesterone and the maintaining of a pregnancy, many doctors give progesterone as injections or pessaries to prevent a miscarriage. But Professor Lesley Regan, in her excellent book Miscarriage, states that "Injections of hormone, in the early weeks of a pregnancy at risk, may prolong the miscarriage but they cannot reverse it. Low progesterone levels in early pregnancy are the result rather than the cause of miscarriage."
Role of sperm in miscarriage
Because it is the woman who miscarries, greater emphasis has been placed on looking at problems in the female reproductive system. But, if you keep miscarrying when nothing wrong can be found, it is logical to wonder if the problem might lie with your partner's sperm. Early studies have shown an increased risk of miscarriage when sperm abnormalities are present in the partner (Int J Fertil, 1962; 7: 17-21).
A study published in the British Journal of Cancer showed that men who smoke, even if their partners don't, run the risk of fathering children who develop cancers such as leukaemia and brain tumours (Br J Cancer, 1997; 76: 1525-31). The theory is that chemicals in tobacco smoke can damage the DNA in sperm. Taking this one step further, it's easy to see that any changes in DNA in the sperm could lead to a possible increase in miscarriage rate. DNA damage cannot be picked up in a normal semen analysis, so this problem would not be seen during routine fertility investigations.
Apart from the possible increase of abnormalities in babies of women who smoke during pregnancy, there is also an increased risk of miscarriages (Am J Epidemiol, 1998; 108: 470-9). Another study, by Professor Jane Golding of the Royal Hospital for Children in Bristol, highlighted how our own bad habits can affect the next generation. Golding looked at daughters who didn't smoke, but whose mothers had. The daughters subsequently suffered a significantly increased risk of miscarriage (Golding J, presentation at a conference on smoking in pregnancy commissioned by the Health Education Authority, 1994).
Drinking can have an enormous impact on the risk of miscarriages. It is universally acknowledged that alcohol can alter a man's sperm count and cause an increase in abnormal sperm (Am J Clin Pathol, 1950; 20: 814-28). It follows that, if an abnormal sperm
fertilises an egg, Nature will try to get rid of that embryo because it is working through 'survival of the fittest'.
Alcohol is a substance known to cause mutations. Studies have shown that alcohol given to female mice immediately after mating caused severe damage to the chromosomes of one fifth to one sixth of the embryos (The Sunday Times, 31 January 1988). This resulted in a higher percentage of miscarriage or death shortly after birth. Chromosomal damage is a recognised cause of miscarriage.