Predicting the date of delivery is a matter of simple calculations, and nothing to be in awe of, writes Nutan Pandit

The young pregnant woman faced her doctor uncertainly, “When was your last period?” he asked, March 25, was the reply. “Hum”, said the doctor, as he paused, and then, ceremoniously announced, “Your baby is due on New Year day”.

The young lady was totally awed. How did he know? What the doctor did was to count seven days from the date of her last period, and arrival at April the first. From this, he counted back three months, March first, February first and January first. And viola!

Many women approach their due dates with great anxiety. Friends who phone and say, “you still around?” only serve to increase the tension while the woman awaits D-day with apprehension..

A lot of fear and apprehension is alleviated by reading about pregnancy, or by attending ante-natal classes.

As for the due one very important fact about it tends to be totally overlooked these days. That is, it is not a date of appointment, it is simply a date arrived at by a rough calculation, to estimate the average duration of pregnancy. A pregnancy might go over it, or terminate before it.

For instance, a woman with a menstrual cycle of 32 days will have a pregnancy longer than, a woman with a menstrual cycle of 28 days. A woman with a regular cycle will deliver more predictably than one with an irregular cycle.

On an average, a pregnancy lasts 280 days, 40 weeks or nine months and seven days, after the first day of menstrual period. That is, for a woman carrying one baby. Twins could arrive three weeks earlier. Generally a pregnancy that goes over two weeks of the due is considered post-mature. However, 40 weeks is merely an average. Maturity may be at any stage from the 36th to 44th week. In spite of the fact that labour which begins before the 38th week is termed pre-mature, and labour beginning after the 42nd week post-mature, these are perfectly normal.

In a study of over 20,000 total births at the University of Chicago, and in a study of 15,000 first births of single infants in Scotland 12 per cent to eight per cent of the deliveries carried more than two weeks beyond the calculated date.

Post-mature babies may lose weight after the term, and be born “thin, caraway and old looking, with loose, baggey skin, long nails, abundance of scalp hair and a singularly alert look.” After birth they soon regain their weight and appear normally chubby. The surface of the placenta in such cases often exhibits thick deposits of calcium.

According to Dr. A.F. Guttmacher, associate professor of obstetrics at John Hopkins, “there are apparently medically authentic cases in which pregnancy extended to 336 days (48 weeks)”.

“When pregnancy is excessively protected there are three possibilities an error of menstrual dates: ovulation several weeks later than the usual fourteenth day at the cycle, impregnation therefore not taking place until 40 to 50 days after the onset of the last menses, or actually several weeks extra at pregnancy beyond the usual 40 weeks.”

The correct answer may never be known.

There is no clear-cut evidence to show whether carrying the baby three or four weeks extra endangers its safety. There are a number of studies which show an increased risk for the foetus, and an equal number which refute the charge.

The best thing to do in such a case would be to let Nature take its course, rather than panic and make your doctor take an unjustified course.

If on an examination, the mouth of the womb is found too “ripe” or ready for labour, the doctor might induce labour.

Dr. Guttmacher feels, “It is difficult to justify ceasarean section for post maturity unless there are complicating factors such as the rare occurence of a baby or extraordinary size which appears too big for safe vaginal delivery or the foetus has been observed to be growing very slowly near or after term is reached.

The chances that a woman will deliver exactly on the 280th after the first day of her last period are a mere five per cent. The chances of delivering either two weeks before or two weeks after the date are approximately 85 per cent.

It is interesting that although the exact reason why labour starts is not known, there is a great amount of evidence that shows that the foetus or placenta produce the hormone which leads to the onset and control of labour. Opinions regarding post maturity are greatly divided. Most obstetricians would not let odema and high blood pressure patients go over term. However, providing everything is normal, there is no harm in allowing a pregnant woman to proceed past its due date by weeks.