Generality
The presumed date of birth ( DPP ) is information that is calculated starting from the first day of the last menstrual cycle to which 40 weeks are added. Knowing the most likely day when the baby will be born allows the future mother to not be unprepared for the event .
The presumed date of birth is also useful for the gynecologist and midwife who are following the woman, to schedule the planned checks (ie the examinations and recommended visits during pregnancy) and to monitor that the development of the fetus inside the uterus proceed according to normal physiological rhythms.
The estimated date of birth is indicative : considering that the calculation is based on the "standard" duration of a pregnancy (on average, 280 days from the beginning of the last menstruation), the menstrual cycle is 28-30 days and the pregnancy proceeds without inconveniences, the actual birth of the child may occur between the two weeks preceding and those following the day considered most likely.
If the cycle is not regular, instead, the gynecologist could " give back " the presumed date of birth based on the parameters measured during the first ultrasound .
What's this
What is meant by Presumed Childbirth Date?
The expected date of childbirth is an estimate of the day when the end of the pregnancy and the birth of the child is most likely .
To carry out this calculation, the doctors refer to the starting day of the last menstruation and take into account that, if it proceeds normally, the gestation has an average duration of 280 days, equal to 40 weeks starting from the date taken as a reference. However, a more physiological pregnancy ends with tranquility even between 37 and 42 weeks .
DPP anamnestic and DPP ultrasound
To date the pregnancy and estimate the day of delivery, the doctor uses the information gathered during the interview with the couple or the future mother ( DPP anamnestica ).
Conventionally, the duration of a pregnancy is calculated in 280 days, starting to count from the day of the beginning of the last menstrual flow, for a total of 40 weeks. At the first prenatal visit, the doctor, through the obstetric ruler, will establish the presumed date of birth, taking into consideration other anamnestic data, such as the average duration of the menstrual cycle or the most probable day of ovulation.
The ultrasound of the first trimester allows to establish the presumed date of the ultrasound delivery ( DPP ecografia ). In practice, based on the findings observed in the early stages of fetal development, the examination confirms the dating of the pregnancy (in women with regular cycles) or makes possible the eventual repatriation (in case of menstrual irregularities or uncertain initial estimate).
How long does the pregnancy last?
- The duration of pregnancy is expressed in 40 complete weeks, which is equivalent to: 280 days or 9 solar months plus a week .
- From the moment of conception to the time of delivery, approximately 266 days (38 weeks) should be spent, if we consider that the duration of the luteinic phase (post-ovulatory) is on average 14 days .
- 40 weeks or 280 days are an approximate period of time, so much so that the parts that occurred slightly in advance or postponement, between the thirty-seventh and the forty-first week of gestation, are still normal .
What is it for?
Presumed Date of Childbirth: how is it used?
The expected date of birth is an indicative value and corresponds to the 40th week of pregnancy . If the pregnancy is physiological (ie there will be no complications), the child could be born in an interval that will go from 15 days before to 15 days after the presumed date of birth.
Why is it useful to know the Presumed Date of Childbirth?
The expected date of childbirth is an important reference to calculate pregnancy times and monitor the stages of fetal development.
Considering that each gestation period corresponds to a specific stage of fetal growth, knowing the day foreseen for the birth of the baby is useful to prepare for the event, indicating to the future mother the deadlines not to be forgotten .
Depending on the presumed date of birth, the gynecologist will then schedule the calendar with the gestating controls (blood tests, checkups, ultrasounds, etc.) together with the pregnant woman.
The expected date of birth is also useful to indicate the ideal care plan for the future mother: a premature baby may need more care, as well as a gestation that lasts over 42 weeks makes it possible to induce labor or a birth cesarean .
To remember
The date of the scheduled delivery is difficult to coincide with the actual date. However, if the menstrual cycles are regular (that is, they occur on average every 28-30 days) and the pregnancy proceeds normally (without problems), the birth can take place at any time included in the 15 days before or after the assumed expiry. During the echography check, the gynecologist will be able to provide a more precise dating based on parameters related to the growth and development of the fetus, confirming or not the dating made with the obstetric rule and / or the calculation of weeks of pregnancy.
How to calculate
Presumed Date of Childbirth: how is it calculated?
The presumed date of birth (DPP) is obtained from the calculation of the weeks of pregnancy through the NAEGELE RULE .
By convention, the calculation of the presumed term of the term delivery refers to the first day of the last menstrual period. Taking into account that a "standard" gestation lasts 280 days, the rule of Naegele is applied, then seven days are added and three months are subtracted to this date. In the case, for example, the starting date of the last menstruation is June 4th, the presumed time of birth will be March 11th of the following year.
During the first gynecological examination after the last menstruation followed by a delay, the gynecologist confirms the beginning of gestation and, to simplify the calculation of the presumed date of birth, uses the OBSTETRIC REGULATION (or wheel of pregnancy) .
The calculation of the weeks of pregnancy can be done already by the couple or by the future mother, before going to the gynecological examination; midwives and doctors can validate or "adjust" the estimate with the obstetric rule, ultrasound check and the results of laboratory tests (including the beta-hCG dosage).
To learn more about How to Calculate Pregnancy Weeks »Rule of Naegele: how does it apply to obtain the Presumed Date of Childbirth?
Naegele's rule for calculating the expected date of childbirth is based on the starting day of the last menstruation and on the "standard" duration of pregnancy, conventionally established in 40 weeks.
In practice, taking as a reference the date corresponding to the appearance of the last menstrual flow, 7 days are added, 3 months are subtracted and a year is added. By simplifying this formula, we add 9 months plus 7 days to the first day of the last menstruation.
The result obtained gives a dating of the week of pregnancy in which the woman finds herself and, consequently, establishes the day in the vicinity of which the birth of the child could occur.
It should be noted that the Naegele rule is based on 28-day menstrual cycles, with an ovulation assumed on the 14th day.
Obstetric rule to estimate the Presumed Date of Childbirth
The obstetric ruler is used by obstetricians and gynecologists to estimate the expected date of birth in a simple way, during the medical history . This instrument is composed of two numbered and overlapping cardboard discs. The lower wheel (larger) and the upper one (smaller) are joined in the center by an eyelet, which allows them to be able to turn independently clockwise and anticlockwise. The lower wheel is divided into 12 sections, one for each month of the year, in turn graded with the days of the month; the lower one shows, instead, 40 weeks of pregnancy divided into the 3 trimesters.
When using the obstetric rule to establish the expected date of birth, the gynecologist takes as a reference the beginning of the last menstruation and takes into account an average gestational duration of 280 days (ie 40 weeks or nine months plus a week) . The doctor spins the lower wheel to position the arrow on the upper disk at the day and month reported by the woman as the start date of the last menstruation, then reads the duration of gestation in complete weeks by default (eg 40 weeks + 6 days = 40 weeks).
In addition to estimating the expected day of birth, the obstetric ruler will also indicate the probable date of conception and the deadlines to be remembered, such as the various check-ups.
Presumed birth date: first trimester ultrasound
The ultrasound of the first trimester is one of the three free echographic checks foreseen by the national health service during pregnancy. This exam, also called " dating ultrasound ", allows to validate the initial estimates of the gynecologist and to correctly date the pregnancy (or give it back, if the presumed birth is too early or late), measuring two parameters: the cranio-caudal length (CRL) and the biparietal diameter of the fetus .
The ultrasound dating should ideally take place within the tenth week of pregnancy. The earlier the examination is performed, the more accurate the calculation of the expected date of birth.
In women with irregular menstrual cycles, the redeployment is possible only in the first weeks of pregnancy, since, during these phases, the embryo has a regular development. Moreover, in these moments, the reference values for fetal development are quite precise and allow to calculate exactly the presumed date of birth. In subsequent ultrasound checks, the gynecologist will indicate the child's measurements in percentile with respect to average growth and the variability is more significant.
Interpretation of the result
Presumed Date of Childbirth: how reliable is it?
The estimated date of the calculated birth is all the more truthful, the more regular the menstrual cycles are: if the average length of menstrual cycles is less than 28 days, the birth could take place slightly earlier; if the interval between one menstrual period and the other is longer, on the other hand, we could give birth with a slight delay.
In women with a regular menstrual cycle, the estimated date of birth estimated with the obstetric rule and Naegele's rule can be considered reliable in providing an approximate calculation of the term of pregnancy and, consequently, an indication from which it could the child is born. It should always be remembered that this is an indication: as the term indicates, the date is "presumed", not "effective" . Gestation lasts 40 weeks on average, but you could give birth on any day starting from the 38th week up to the 42nd week .
In any case, the estimate of the presumed date of birth is a starting point: this information can be established with a better approximation by means of an ultrasound check and the other medical tests that are performed during gestation.
Presumed date of birth from conception: note
Conception takes place when the spermatozoa, going up the uterus, reach the mature egg cell, released from the ovary during ovulation and available for fertilization. Theoretically, for the calculation of the presumed date of childbirth it should be counted starting from this moment . However, it is practically impossible to know with certainty on which day the conception occurred: even if there was only one unprotected sexual relationship in the fertile period, fertilization does not always take place at the same time.
The mature egg cell can be fertilized from 4-5 days before until 1-2 days after ovulation. This is possible in consideration of the fact that the ovule, when it is expelled from the ovary, manages to survive for about 24 hours, while the spermatozoa can remain viable in the female genital apparatus up to 72-96 hours. Therefore, unprotected sexual intercourse even 3 or 4 days before ovulation can lead to fertilization.
For this reason, the calculation of the expected date of birth is estimated 40 weeks from the first day of the last menstrual period, which should have occurred about 2 weeks before conception.
