HOW PREGNANT AM I?
There are several ways of working this out. The most common is by dates. The first day of your last period is counted as day 1, and an average pregnancy is about forty weeks. The ‘expected due date’ is calculated in this way. Most babies arrive between thirty-eight and forty-two weeks, not necessarily on their ‘due date’.
If your first missed period was two weeks ago, you would be about six weeks pregnant, because it is counting from your last real period, (only thirty-four weeks to go!). This method assumes that most people have cycles of about four weeks and regular periods, as most people do.
However, if you have a usual cycle of five weeks, and your missed period was two weeks ago, you may not be seven weeks pregnant (which you would be by counting from your last real period). You are more likely to be six weeks, because most women ovulate about two weeks before their period, regardless of how long it is between periods. If you have irregular cycles it may be impossible to tell the gestation (stage of development of the pregnancy) from the dates alone.
It is generally not absolutely necessary to know the exact gestation. If it is, then an early (less than ten weeks) ultrasound can be used to assess gestation. This measurement will be accurate to within a few days.
Less accurate, but still useful, is a physical examination. The size of the uterus can give an idea of how far the pregnancy has progressed. The limiting factors in this method are the experience of the doctor performing the examination and the fact that the uterus may not be that easy to feel.
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