Experiencing a miscarriage can be a devastating, but not an uncommon, outcome to a much-wanted pregnancy. Unfortunately, around 15% of pregnancies in women under 35 years old will result in a miscarriage.
Recurrent miscarriage is defined as three miscarriages in a row, and can affect up to 1% of women. Even after a woman has had three miscarriages, there is still as greater chance of the next pregnancy continuing, than having another miscarriage.
The most common cause of miscarriage is that the pregnancy is not normal. Mostly, this is due to an abnormal chromosome pattern (too much or not enough DNA required for a healthy baby).
As women age, their eggs undergo chromosomal damage, so there is a higher chance of miscarriage. By the age of 40, the miscarriage rate is 30%, and by 41, the miscarriage rate is over 40%. Increasing male age is also associated with increasing DNA damage to sperm and miscarriage.
Rarely, an individual may have a pre-existing chromosome abnormality (translocation), which predisposes them to recurrent miscarriage. This can be assessed via a blood test for both partners.
The chance of miscarriage may be increased if there is a gynaecological condition affecting the shape or structure of the uterus.
Most commonly, this could include fibroids and polyps. Less commonly, a woman may be born with an anatomical abnormality of the uterus, such as a bi- or uni-cornuate uterus, or a uterine septum. These conditions are usually diagnosed via a specialist gynaecological ultrasound. Some of these problems may be able to be corrected via surgery.
It is also possible to develop scar tissue (adhesions) within the uterus that could lead to miscarriage. This may occur as a result of a previous gynaecological or obstetric procedure. Fluid may need to be injected into the uterus (either awake or asleep) to diagnose this problem.
Any untreated medical condition can lead to miscarriage.
While most women with serious medical conditions will already be seeing a physician, there are some medical conditions which may not be suspected or diagnosed until after a woman has had a few miscarriages. These could include diabetes, thyroid disease (both under- and over-active thyroid), as well as other auto-immune diseases.
Some women are concerned that low progesterone levels may contribute to a miscarriage. This can be difficult to establish as progesterone levels are often low when a miscarriage occurs, and may simply reflect that the pregnancy is not continuing, rather than being the actual cause of the miscarriage. In some cases, women may be advised to take extra progesterone (vaginally) during the first trimester of pregnancy.
Lifestyle factors may also contribute to miscarriage.
Being either over or underweight both have a negative impact. Excessive exercise, smoking, alcohol and caffeine consumption have all been linked to miscarriage and infertility.
Even after three miscarriages, most women will have normal investigations.
These include hormone blood tests and a specialist ultrasound for the woman. Further blood tests for blood clotting and immune disorders in the female can be considered, as well as chromosome (karyotype) testing for both partners.
A hysteroscopy and laparoscopy (for the woman) is also useful and may diagnose polyps, adhesions, anatomical abnormalities and tubal problems that may have been missed, even if previous ultrasounds have been normal.
If a woman is having a curette to manage a miscarriage, she can speak to her doctor about sending the tissue for chromosomal analysis.
Sometimes there is a definable problem which can be addressed with medications or surgery.
There are some studies which suggest that intensive monitoring in the first trimester may lower the chance of recurrent miscarriage. Initially, this may involve weekly blood tests to assess the pregnancy hormone and progesterone levels, and then regular ultrasounds from 7 weeks onwards. Sometimes, additional progesterone or blood thinning medications may be prescribed.
Patients with a known chromosomal abnormality or who have had miscarriages with proven chromosomal abnormalities, may choose to do IVF with pre-implantation genetic screening (PGS). This involves creating embryos via IVF, and growing them to the blastocyst stage, at which time one or two cells are removed from the embryo. The embryos are frozen, and the cells are sent for further testing to identify those with a normal chromosome pattern. If a woman transfers an embryo that has been identified as normal after PGS, then her chance of miscarriage is significantly decreased, even if she is older. PGS is fast becoming a popular choice for many patients.
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