When a woman knows she is pregnant, she starts calculating when she will be born. It is nine months from the last rule, or to be more exact, 280 days. This calculation can easily be done at any time and then, on the first ultrasound, the gynecologist adjusts the estimated due date When taking the baby's measurements.
Now, that date, the day the woman "goes out of accounts", ends up being the unlikely date of childbirth, because only 4% of women give birth on that date. Then you start talking about the baby getting ahead, or that the baby is getting late, when it turns out that The normal duration of a pregnancy can vary up to 37 days.
We are not talking about anything new, a baby is born at term when it arrives after 38 weeks of gestation and before reaching 42 weeks. Before it would be pre-term and then post-term. This already gives a variability of four weeks, 28 days, in which a baby can be born without being considered to be out of the normal term.
Now, a recent study published in the magazine Human Reproduction He wanted to specify a little more the figures and it concludes that the duration of labor, comparing normal deliveries, not counting premature births, may vary up to those 37 days we have commented.
Study Data
The study was conducted by researchers from the National Institute of Environmental Health Sciences of the USA (NIEHS) and aimed to know how much pregnancy can vary in humans and how they could affect hormonal variations in that duration.
To do this, they took the data of the participants of the Early Pregnancy Study, a study that was done with 130 women who, between 1982 and 1985, stopped taking contraceptives to become pregnant. They took data from those who became pregnant with only one baby and who also offered hormonal data from the first moment, with daily urine samples.
The total number of women who came to study is 125 women, which is a very small sample to consider the reliable conclusions, new studies being necessary, with larger samples, to confirm the data.
Conclusions of the study
The first conclusion is that we all know, that believing that the probable date of delivery is the day when the baby should be born is a mistake, because then future mothers are distressed if the baby does not arrive, the family keeps asking if The baby is not yet born, they begin to recommend you to walk, to dance, to make love, acupuncture, take herbs and, if you hurry me, make the bridge pine if with this the baby will be born before. That it is not bad, that except the bridge pine nothing will harm her, but that it can distress and worry the pregnant woman unnecessarily when it turns out that the pregnancy is simply a little longer than average, probably being normal.
Other research findings were that older women in the sample tended to give birth laterThat is, their pregnancies were longer. To put it in figures, they calculated that each year of the mother's age added a day of gestation. They also saw that the women who had weighed the most at birth also had longer deliveries, the calculation being one more day per 100 grams. The duration of previous births also helped to predict the duration of labor, since when the previous births had been long, the following were also long.
At the hormonal level, they saw that when women took longer to experience a rise in progesterone, pregnancies were an average of 12 days shorter than those of the rest. In addition, they noticed that when the egg took longer to implant, the pregnancy also lengthened.
In the words of Anne Marie Jukic, lead author of the study:
Emphasizing a due date can make the duration of a pregnancy more predictable than it really is. Our results suggest that this duration is very variable even in healthy pregnancies ... We were slightly surprised by the 37 days of difference in childbirth that may exist between pregnancies of which the ovulation date is perfectly known. Until now, this variation had been attributed to errors in the determination of gestational age, but our study discards it. It is fascinating.
Now, from this study and with subsequent investigations that can confirm the data, it may be necessary rethink how to calculate the probable date of delivery adding the commented factors (age of the mother, weight at birth, etc.) and changing the date, perhaps, by an interval: your baby will be born, probably, between these two days, to avoid anxieties and environmental pressures.
