Are You Pregnant?

Following are some the most frequent questions women ask who want to know if they are pregnant. For example: what are the symptoms that suggest a pregnancy? How do I calculate the day of conception? What is my likely due date? What are laboratory methods based on and how reliable are they?

Before anything else, it is necessary to understand how the normal female reproductive cycle functions. The menstrual cycle of a woman lasts approximately28 to 30 days. An egg is released from one of the woman's ovaries at the approximate midpoint of the menstrual cycle, that is to say, about 14 days after the onset of menstruation. The first day of menstruation is considered the first day of the cycle, and from that day one counts 14 days. This is the women's most fertile period.

The egg travels down the fallopian tube (these are canals connecting each of the ovaries to the uterus or womb) and reaches the uterus. If the egg is not fertilized by a sperm, the uterus loses its wall or lining, and what we know as bleeding, menstruation or a "period" occurs. 

In reality, pregnancy begins when a male cell or sperm reaches the egg and fertilizes it after it has left the ovary, transforming into an embryo. This then attaches to the interior wall of the uterus and begins to grow, later transforming into a fetus.

You should suspect pregnancy when:

  1. There is no menstruation, two weeks after missing a menstrual cycle (that is, a delay of two weeks from the date on which menstruation is expected).
  2. Nausea, vomiting and dizziness occur: these symptoms generally appear several weeks after the beginning of the pregnancy. The symptoms are caused by an increase in the amount of hormones circulating.
  3. Your abdomen grows: an increase in the size of the lower part of the abdomen (womb) generally occurs during the 3rd or 4th month of pregnancy.

What is the probable delivery date?

As previously mentioned, pregnancy begins at about the middle of the menstrual cycle, that is 14 days after the onset of the last period. In reality, this date is not exact and pregnancy may occur at any time during the menstrual cycle, especially in women with irregular cycles. The 14th day of the cycle is considered "the most fertile," due to the fact that the chances of becoming pregnant increase on the days closest to the middle of the menstrual cycle.

The probable due date, especially in women with regular menstrual cycles, may be calculated using the following rule:

PROBABLE DUE DATE = (Date of the Last Menstruation 7 days) - 3 months

For example, for a woman whose last menstrual cycle began on the 14th of July, the probable delivery date will be the 21st of April of the following year.

Laboratory Methods

Most doctors recommend carrying out pregnancy tests in a lab as proof of the pregnancy. These tests are based on the detection of certain hormones produced during pregnancy. As the pregnancy progresses, the amount of hormones produced in the blood is much greater, therefore the test will be much more reliable.

The majority of labs has reactive agents that detect very low concentrations of this hormone and, for this reason, can diagnose pregnancy in the very early stages (approximately 4 weeks after missing the last period). Other methods are even more sensitive, and are capable of detecting pregnancies after the second or third week of pregnancy.

The same hormone detected in the blood is also found in the urine (although in lower concentrations) and the "home" pregnancy tests are generally based on the detection of this hormone. Some of these kits can detect pregnancy after the first day of a late menstruation.

If you have any doubts about your menstruation or the possibility of pregnancy, consult your doctor.

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