WOMEN’S BODIES: CONCEPTION. CONFIRMING PREGNANCY
Conception
A new life begins when an ovum is fertilised by a sperm. Of the 200-400 million sperm in an ejaculation, only around a hundred make the 10-12 cm journey (which is believed to take about an hour) through the cervix and uterus to the outer part of the tube, and only one of these penetrates the ovum.
There’s more to conception than fertilisation. The fertilised egg, a single cell, must then travel down the tube to the uterus, dividing into many cells on the way to form a fluid-filled ball called the blastocyst. About three to four days are spent on the journey from fertilization to implantation site. Here the blastocyst buries in the lining of the uterus (endometrium). Within hours the placenta begins to form and conception is complete.
It’s believed that not every fertilised ovum implants. During if through the tube, the cells formed by its division release a protein called Early Pregnancy Factor (EPF) that changes mother’s immune response so that embryo won’t be rejected. EPF can be detected after ovulation in the bi women who don’t conceive.
For convenience, how far pregnant you are is stated in weeks from the beginning of the last normal menstrual period (LMP), which for most women is a certain date. It also marks the date when the egg began to mature. However, the LMP date is two weeks before the time of fertilisation, and about three weeks before the time of implantation.
A simple way to work out your expected date of delivery (EDD) is to add 10 days and 9 calendar months to the first day of your LMP date. For example, if your LMP date is 15 July, your EDD will be 25 April. In fact, only 5 per cent of women deliver on the EDD, but 80 per cent deliver within 10 days either side of it.
Confirming pregnancy
Gone are the days when we had to rely ; on an examination three to four weeks after a missed period to diagnose pregnancy. Pregnancy tests have become increasingly sensitive over the past decade. The developing placenta begins to produce pregnancy hormone within 24 hours of implantation. The newer blood tests can detect this hormone from the ninth day after ovulation, four to five days before your period is due. New urine tests (including some home tests) can confirm pregnancy from the eleventh day after ovulation. However, because it’s generally hard to be certain about the exact day of ovulation, results of these tests are not reliable until the date your period would have been due. And if for some reason you ovulated late (say, three weeks after the LMP date), a false negative result could come up for several days after the next period is due.
Apart from your burning curiosity, or if you’ve previously had problems very early, there’s generally little point in testing for pregnancy before or for a week or so after you miss a period, except for making changes in your lifestyle to safeguard the pregnancy: if you intend to give up smoking (you should!) and be careful with alcohol and other drugs (including medicines) when you’re pregnant, it’s best to do so as early as you can.
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