The expectation of a good outcome for pregnancy begins very early. When a woman first feels her body changing as another life grows within, the attachment to her baby begins, her partner sharing the joy and anticipation of this new life. It is understandable, therefore, the devastation and grief experienced when a miscarriage happens. Unfortunately miscarriage is the most common complication of pregnancy and many people will not realise that most pregnancies do indeed end in miscarriage. As wonderful as Nature may be, she is not very efficient in the process of reproduction.
For a normal fertile couple, around 60% of natural cycles will result in conception but one half of these will fail to implant into the womb lining (endometrium). After implantation when a pregnancy is clinically recognised, at around 7 weeks from the last menstrual period (LMP), the risk of miscarriage is about 15%. After 8 weeks from LMP the risk is around 10% and after 13 weeks, 4% of pregnancies will end in miscarriage.
Miscarriage happens mainly because of a problem in the mixing of genetic material from the egg and sperm. In around 60% of cases there is an extra gene (trisomy), a missing gene (monosomy) or an extra whole set (triploidy). Even if we looked very carefully for a cause, in many cases none can be discovered. Of course this doesn’t mean that there isn’t a reason, it just means that our understanding of conception and implantation is inadequate to explain it. Other things found to be associated with an increased risk of miscarriage include major disease (e.g. diabetes, epilepsy), twin pregnancies, excess alcohol intake, heavy physical stress and exposure to organic solvents. Smoking less than 13 cigarettes per day is associated with an increase in risk of about 30% above average, and more than 14 per day, a 60% greater risk. Previous use of the contraceptive pill seems to be protective against miscarriage. Compared to women under the age of 35y, those over this age are approximately twice as likely to miscarry and over the age of 40y this risk is increased four-fold.
A woman’s previous pregnancy history has an effect on the risk of miscarriage. For a woman in her first pregnancy, once clinically recognised, the risk of miscarriage is about 5%. If a woman has had a previous miscarriage, this is increased to 20%, after two it is 28% and following three previous miscarriages it is 43%. Put another way, even after two miscarriages, there is over 70% chance of pregnancy success. This information comes from the Recurrent Miscarriage Clinic at St Mary’s Hospital in London, who have published much in this field.
Recurrent miscarriage is a medical term describing when a woman has miscarried three successive pregnancies in a row. It is usual to perform some investigations if this happens to see if there is an underlying cause. After two miscarriages it is very unlikely that any reason will be discovered – from the statistics above one can see that around 1 in 35 women will have two miscarriages in a row and it is due to nothing more than very bad luck. Of course this knowledge does little to soften the blow when it happens.
It is increasingly more common for GP’s to refer women with bleeding in early pregnancy to hospital for an ultrasound scan to try and determine what is happening. The most useful type of scan in the early stage is a transvaginal one. A slender scan probe is covered with a condom and some lubricant gel and placed just inside the vagina. This means that a full bladder and its associated discomfort is avoided and results in much better quality images. Most women do not find this type of scan too uncomfortable. Typically a high-resolution scan should be able to see the pregnancy sac at around 4-5 weeks from LMP, the fetus will be visible from 5.5-6 weeks and a heartbeat may be seen around 6-7 weeks. Although the date of the last menstrual period will usually be known, even women with a regular cycle may not consistently ovulate mid-cycle and this will alter the true gestation length. Because of this, very early scans must be interpreted with caution and many doctors will suggest another scan in 7-10 days to clarify the situation if the first scan was not reassuring.
Sometimes scan findings can tell unequivocally that miscarriage has happened, even though little bleeding has been seen. For example, if a woman had her first positive pregnancy test four weeks ago and scans only shows an enlarged but empty sac, this is not compatible with an ongoing pregnancy. Miscarriage doesn’t always reveal itself with bleeding or pain and many women experience what is called a ‘missed miscarriage’. The causes are the same as usual and it has no particular relevance to prognosis for next time.
Once miscarriage is confirmed, there are several options for management. Previously all women were advised to have a dilatation & curettage (D&C – also called an evacuation) to avoid heavy bleeding or infection. Recent studies have demonstrated the safety of other options. Conservative management or letting nature take its course, for selected cases will avoid surgery in 80%, with no increased risk of infection, prolonged bleeding or pain. If things have not resolved within a few days, some form of active treatment is advised. Another option is medical treatment, using a drug called misoprostol, which helps the body to complete the miscarriage. This is sometimes used with a tablet called Mifepristone if it was a missed miscarriage. For miscarriages under 10 weeks gestation, 92% of women will not need surgical treatment when given appropriate medical treatment, without any increase in infection risk.
When offered a choice in how to manage miscarriage, one third of women choose the surgical option and only 20% are immediately interested in medical treatment. This may be because many women have not heard of medical treatment or prefer an immediate resolution of the situation. Hopefully, with adequate counselling, more women will chose this option, avoiding the small but definite risks of surgical treatment.
Although miscarriage is extremely common, its effects on a couple can be devastating. It is often difficult to accept, but reassurance is very appropriate as most miscarriages happen by chance alone and do not have long-reaching consequences for health, fertility or eventual success. It is Nature’s way of ensuring that when you are successful, your baby has its best chances for the remainder of pregnancy and its lifetime after birth.
Article by Dr Danny Tucker.
Further information on miscarriage can be found at the Pregnancy & Women’s Health Information site at http://www.womens-health.co.uk