The first question every woman asks when the doctor confirms that she is pregnant is ‘when is my baby due?’ Most doctors have a colorful wheel, or a calculator, which counts 266 days from the moment of conception, or 280 days from your last period. Other doctors will honestly tell you that this calculation is only an estimate, and that only baby knows for sure. Two weeks plus or minus the calculated due date is considered normal. And there are many other things that can change this calculation.
Why is Dr Naegele Wrong?
The calculation for the baby due date came to us from Dr. Naegele, a German obstetrician from Heidelberg. In 1850 he determined that the length of normal human gestation is 266 days from the moment of conception. His assumption was that an average woman has a 28 days long menstrual cycle and that all women ovulate on the 14th day of their cycle. So, his calculation for the baby due date was to take the date of last period, add seven days and deduct three months. The result is your due date.
We learned since that many Dr. Naegele”s assumptions were wrong. One of them is that not every woman ovulates on the 14th day of their cycle. The cycle length varies greatly from woman to woman. Different ethnic groups have different gestation length. Scientists found that white women, women aged 19 to 34 and women going through first pregnancy have longer gestation time from black women, women younger than 19 and older than 34 and women that already went through birth. Another study also shows that African and Asian women have shorter gestation time than Caucasian women.
Many other things changed since Dr. Naegele”s time to affect the length of our gestation: our prenatal care and nutrition are much better now, making pregnancy last longer.
Why should we care?
The new knowledge about what affects our gestation length helps doctors to calculate our due date more precisely. Actually, more precisely than two weeks plus or minus. At the beginning of the pregnancy, a few days difference does not look like much. But, as the pregnancy progresses, you can”t wait to get it over with and have your baby in your hands. On the more serious side, there are times when the exact date is very important ” “ when the birth has to be induced because of baby”s or mother”s health.
The use of ultrasound
While we still use Dr. Naegele”s Rule to determine the approximate due date, there are other, more precise methods at our disposal. One, very common and well known, is ultrasound. High frequency sound waves are used to ” ˜see” ™ directly in the womb. If conducted early, ultrasound test can give us very precise measurement of the baby and almost exact due date. But, some research shows that ultrasound tests are not without risks and should not be conducted without serious reason, such as potential abnormalities or problems with baby. Women who do not know the date of their last period, because they continued to have period during pregnancy, or had ovulation spotting they took for period, have to undertake ultrasound in order to determine the exact due date. Others, if all things are well and there are no signs of any problems do not need to undergo ultrasound just so that they would have their baby early photo. The technology is determined safe, but is not researched enough to be completely sure of it.
Whatever the method your doctor used to calculate your due date, do not forget that two weeks plus or minus from that date is a normal variation. Try to stay calm, your stress will help neither you nor the baby. First time mothers are notorious for pushing it to the limit. Your doctor will monitor your baby”s vital signs to make sure that everything is OK, and will be able to tell you if there is a reason to induce labor if the baby is just not willing to do it on his or her own.