Naegele's Rule Research Articles

Naegele's rule and the length of pregnancy - A review.

The proposition that a pregnancy is 40weeks or 280days in duration is attributed to the German obstetrician Franz Naegele (1778-1851). His rule adds nine months and seven days to the first day of the last menstrual period. The expected date of confinement from this formula is approximately right in the majority of cases. However, the idea that this rule can apply to every pregnant female - young or old, nulliparous or multigravida, Caucasian, Asian, African, or Indigenous - stretches credulity. In addition, many women regard the 40-week date as a deadline, which if crossed, may then place the baby under stress. Forty weeks is such a simple, round, convenient figure that it has proved difficult to challenge, despite criticism. Nonetheless, what might have been an appropriate formula in Germany in the 19th century deserves to be revisited in the 21st. To review the length of pregnancy, in the light of current technology, in particular ultrasound scanning, and assisted reproductive techniques. A Medline search was performed for variables on the length of pregnancy, the expected date of confinement, and prolonged pregnancy. A number of factors were found to significantly influence the length of a pregnancy, including ethnicity, height, variations in the menstrual cycle, the timing of ovulation, parity and maternal weight. Naegele's rule should be considered as a guideline for the expected date of confinement, and not a definite date.

The impact of birth anesthesia on the parameters of oxygenation and acid–base balance in umbilical cord blood

Background: There is a great number of studies dealing with the impact of birth anesthesia on the course of labor and condition of the newborn. The aim of this study was to investigate the impact of birth anesthesia on the parameters of oxygenation and acid-base balance in umbilical cord blood.Methods: Subjects were divided into four groups: vaginal delivery without anesthesia, vaginal delivery with epidural anesthesia, delivery by cesarean section under a subarachnoid block, and delivery by cesarean section under general anesthesia. The study included mothers aged 18–45 and their newborns born from a singleton normal pregnancy lasting 37–42 weeks, calculating the date of birth according to Naegele's Rule, which was confirmed by ultrasound assessment. The inclusion criteria were a birth weight between 2800 and 4100 gResults: Hematocrit, total hemoglobin, blood oxygen capacity and carboxyhemoglobin content (umbilical artery and vein mean values respectively in all study groups: 41.9 and 42.6%, 14.3 and 14.5 g/dl, 19.3 and 19.6 ml/dl) were similar in all groups and did not correlate with pH in either group. The mean pH value of umbilical cord arterial blood in the “vaginal delivery with epidural anesthesia” group was 7.27 and was significantly the lowest (p < .05) of all the examined groups, in the remaining groups, the mean values ranged between 7.29 and 7.30. Hemoglobin oxygen saturation, oxygenated hemoglobin content, and total oxygen content in umbilical cord blood were statistically significant (p < .001), almost twice as high in cesarean sections under general anesthesia than in cases of regional anesthesia regardless of the method of delivery. Vaginal deliveries had intermediate values of oxygenation parameters.Conclusion: Blood oxygenation of the fetus is a very good parameter to evaluate the clinical state of the baby. Due to most common hypotension of the mother by the regional anesthesia (subarachnoid or epidural), which is compensated by the application of the vasoconstrictors or only by the fluids, it comes to decrease in the oxygen supply of the fetus. We consider in this study that the general anesthesia can be, in some cases, more indicated than the regional anesthesia. The decision of which kind of anesthesia should be used needs to be made by the anesthetists and also by the obstetrician because it can affect the neonatal state after the delivery. It also needs to be mentioned that the time between the start of the anesthesia and the extraction of the fetus by the cesarean section should be as short as possible.

Naegele's rule revisited

Recent literature suggests that Franz Carl Naegele's (1778–1851) rule for estimating the date of delivery has been misinterpreted, resulting in this being brought forward by five days. Baskett and Nagele's work underpinning this argument has become widely accepted and quoted in obstetrical and midwifery textbooks. However, our re-examination of Naegele's original statements does not support the recent findings. On the contrary, the original textbooks of Naegele clearly advise taking the first day of menstruation for the calculation of the date of delivery.

The secular growth acceleration: does it appear during fetal life?

Objective: To test if secular growth acceleration occurs during fetal life.Methods: ANOVA Kruskal–Wallis and Mann–Whitney U-test have been used for the biometric characteristics comparison of nowadays fetal population with those three decades ago and to test the hypothesis about the existence of secular growth acceleration during fetal life. For this purpose, we first calculated mean values of particular biometric parameters for the whole pregnancy. During the period 2002–2009 biparietal diameter, fetal length and abdominal circumference measurements in singleton uncomplicated pregnancies between 22 and 41 gestational weeks were obtained. Gestational age was estimated according to Naegele's rule and confirmed with an early ultrasound examination. Pregnancies with fetal cromosomopathies and malformations were excluded as well as those resulting in perinatal death.Results: There were no statistically significant differences of the examined fetal biometric parameters measured by ultrasound between contemporary fetal population and those from 35 years ago.Conclusion: Our investigation did not undoubtedly prove that significant changes of fetal biometric parameters occurred in the last three decades. It is possible that secular growth acceleration does not exist in prenatal period but also the observed time period could have been short for this phenomenon to manifest.

Pregnancy dating – why, when and how

The calculation of gestational age and the expected date of delivery is not just a social issue but have considerable medical implications. For many centuries it has been accepted that the normal gestation period for humans is ten lunar, or nine calendar months. Franz Carl Naegele (1778-1851), Professor of Obstetrics at the University of Heidelberg, is credited with developing a simple calculation to determine the EDD by adding 7 days to the first day of the LMP and then subtracting 3 months1. This calculation commonly referred to as Naegele's rule and has been routinely used to date the pregnancy.

Erroneous calculation of the expected date of delivery by medical professionals

Background: Naegele's rule, which is used to estimate the expected date of delivery (EDD), presumes that the subject is menstruating regularly every 28 days. For subjects with lengthier or shorter cycles, correction is needed while calculating the EDD. A majority of medical professionals are unaware of this and succumb to errors. The author has published Parikh's formula as an alternative that does not require any additional correction. This study was aimed at evaluating awareness among medical professionals regarding the importance of menstrual history and utility of Parikh's formula in minimizing errors. Materials and Methods: One twenty-six medical students and interns from four medical colleges in India and 24 medical officers from a primary health center were enrolled for the study. A questionnaire with a history of a woman with a regular cycle of 35 days was distributed to each participant and they were asked to calculate the EDD. Participants were then educated on Parikh's formula and asked to calculate the EDD again by using that formula. Results: Only 10 (6.66%) of 150 participants calculated the EDD correctly by using their conventional methods. After explaining Parikh's formula, this proportion raised to 99%, i.e., 147 of 150 participants, the difference being statistically significant at P Conclusion: A majority of students, interns, and medical officers are unaware of the importance of previous menstrual history while calculating the EDD. If Parikh's formula is used, errors in calculating the EDD can be reduced significantly.

Historical notes on immaturity. Part 1: Measures of viability

The interest in the limit of viability originated from various sources, including legal requirements, the rejection of mechnical life support, competition for resources, concerns about handicaps, and proximity to the fetus with its limited rights. Gestational age was determined from menstrual history by Hippocratic writers, who established the tenacious idea that 7-, but not 8-month infants could survive. Naegele's rule, already published by Boerhaave in 1744, was correct when applied to the last day of menstruation. Birth weight and length were not measured until the end of the 18(th) century. This remarkable disinterest resulted from superstition, grossly inaccurate measurements by the authorities Mauriceau and Smellie, and the conversion chaos of the pre-metric era. A table is provided with historic mass and length units allowing to determine birth weight and body length in the older literature. The idea of viability is a remnant of vitalism, a medical doctrine popularized in 1780 by Brown. Many short-lived statements defined its limit, but until now what was meant by viability remained nebulous.

Naegele's rule: a reappraisal.

The origin of Naegele's rule to calculate the expected date of confinement is reviewed. It is possible that the rule has been misinterpreted, resulting in an earlier estimated date of delivery with implications for induction of labour for post dates pregnancy.

Re: do we need to modify Naegele's rule?

Re: do we need to modify Naegele's rule?

Evaluation of ultrasound-estimated date of delivery in 17,450 spontaneous singleton births: do we need to modify Naegele's rule?

To compare the size of error in the predicted date of delivery by biparietal diameter (BPD) and last menstrual period (LMP) in different clinical models. Predicted dates of delivery were calculated in 14,805 spontaneous deliveries with a reliable date of LMP using two assumptions: average length of pregnancy of 280 and of 282 days. Errors in these calculated dates were tested when used alone or combined, i.e. the LMP-predicted date of delivery was used as first choice unless the discrepancy between gestational age calculated by BPD and LMP exceeded 7, 10 or 14 days. The average discrepancy (error) between predicted date of delivery from BPD and LMP and date of spontaneous delivery was 7.96 and 8.63 days, respectively (p < 0.0001). Adding 282 instead of 280 days to the first day of the LMP reduced the error of the LMP method from 8.63 to 8.41 days, reduced the percentage of classified post-term deliveries from 7.9 to 5.2% and increased the preterm births from 3.96 to 4.48%. No models of combined use of LMP and BPD were superior to the use of BPD alone. If both BPD and LMP are available, BPD should be used to predict term. If only LMP is available, term should be calculated as the first date of the LMP plus 282.

Predictors of human gestational length

Our objective was to identify statistically significant variables that determine the length of human gestation. Multiple linear regression was used to analyze 9355 observations from the Delivery Interview Program, a cross-sectional study conducted from 1977 through 1980 at the Boston Hospital for Women (now called the Brigham and Women's Hospital). Maternal parity, age, and race were found to be the most important variables determining the length of human gestation. Multiparous women, women aged < 19 or > 34 years, and black women were found to have shorter gestations than primiparous women, women aged 19 to 34 years, or white women. By means of our linear model the length of pregnancy for women with different risk factors can be estimated more precisely than Naegele's rule allows.

Can we abandon Naegele's rule?

A pregnant woman may become anxious if she has not delivered by the date given to her by her physician. Much anxiety would be alleviated if a range of dates (38-42 weeks) was substituted for a specific date of delivery. 1

Dating pregnancy Gathering and using a reliable data base

This study sorts common variables used in dating pregnancy and ranks them according to their level of accuracy. The more accurate predictors, eg, LMP, should need no further corroboration during the course of pregnancy as long as the clinical course remains congruent with gestational length. Less accurate variables, eg, first fetal heart tones or fundal height need further confirmation in the absence of a useful menstrual history. New research is presented on uterine height correlation with gestational age, within the context of related research. Since discrepant uterine size is the most commonly cited reason for ordering ultrasound during pregnancy, this variable was examined in terms of its correlation to gestational age in an effort to define the discrepancy so often cited. Results lead to the conclusion that there is a lack of research data justifying the practice of equating weeks of gestation and centimeters of fundal height. In fact, the data indicate a healthy range of variation and a general tendency for the uterine height to be less than weeks of gestation. The length of the average term pregnancy is examined, with discussion of clinical implications. A management tool is offered to aid the clinician in deciding when further information is needed for a reliable data base. The usefulness of a singular EDD derived by any formula is discussed and the age old Naegele's rule is critically examined and compared to modern studies.

Further studies on the oxytocin-oxytocinase system

The dynamic oxytocin test and the chemical assay of serum oxytocinase were carried out in 426 pregnant women with the aim of predicting the date of labor. In cases in which the oxytocin dynamic test showed decreasing values or rising levels of oxytocinase, conservative procedure was followed. In the remaining cases labor was induced by means of Syntocinon. In the prenatal period oxytocinase levels show steady increase in 79.9 per cent of cases, while the values of the oxytocin test decrease in 87.2 per cent. Both situations were observed simultaneously in 76.6 per cent of cases. Prediction of the date of labor by this biochemical method is 9 times as accurate as the prediction based upon Naegele's rule.