Estimated date of delivery

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The estimated date of delivery (EDD), also known as expected date of confinement, [1] and estimated due date or simply due date, is a term describing the estimated delivery date for a pregnant woman. [2] Normal pregnancies last between 38 and 42 weeks. [3] Children are delivered on their expected due date about 4% of the time. [4]

Contents

Origins of the term

Confinement is a traditional term referring to the period of pregnancy when an upper-class, noble, or royal woman would withdraw from society in medieval and Tudor times and be confined to their rooms with midwives, ladies-in-waiting and female family members only to attend them. [5] This was believed to calm the mother and reduce the risk of premature delivery. "Lying-in" or bedrest is no longer a standard part of antenatal care.

Estimation methods

Due date estimation basically follows two steps:

Estimation of gestational age

According to American College of Obstetricians and Gynecologists, the main methods to calculate gestational age are: [7]

Estimation of gestational age at childbirth

Childbirth on average occurs at a gestational age of 280 days (40 weeks), which is therefore often used as a standard estimation for individual pregnancies. However, alternative durations as well as more individualized methods have also been suggested. There is in any case considerable variation among individual pregnancies.

Variability

Distribution of gestational age at childbirth among singleton live births, given both when gestational age is estimated by first trimester ultrasound and directly by last menstrual period. About 80% of childbirths occur between 37 and 41 weeks of gestational age, with a somewhat more narrow span when based on first trimester ultrasound. Distribution of gestational age at childbirth.svg
Distribution of gestational age at childbirth among singleton live births, given both when gestational age is estimated by first trimester ultrasound and directly by last menstrual period. About 80% of childbirths occur between 37 and 41 weeks of gestational age, with a somewhat more narrow span when based on first trimester ultrasound.

Given that these gestation lengths are only estimates of an average, it is helpful to consider gestation time as a range of dates rather than as a single "due date". The median is merely a guideline for the day at which half of all births occur earlier, and half of all births occur later. Births rarely occur on a due date, but they are clustered around due dates. [12] A study of singleton live births in the US came to the result that childbirth has a standard deviation of 14 days when gestational age is estimated by first trimester ultrasound, and 16 days when estimated directly by last menstrual period. [11]

Naegele's rule

Naegele's rule is a standard way of calculating the due date for a pregnancy when assuming a gestational age of 280 days at childbirth. The rule estimates the expected date of delivery (EDD) by adding a year, subtracting three months, and adding seven days to the origin of gestational age. [13] [14] The result is approximately 280 days (40 weeks) from the start of the last menstrual period. Another method is by adding 9 months and 7 days to the first day of the last menstrual period.

Naegele's rule is named after Franz Karl Naegele, the German obstetrician who devised the rule. Naegele was born July 12, 1778, in Düsseldorf, Germany. In 1806, Naegele became ordinary professor and director of the lying-in hospital in Heidelberg. His Lehrbuch der Geburtshilfe, published in 1830 for midwives, enjoyed a successful 14 editions.

Here's the formula to calculate your Estimated Due Date using Naegele's rule :
Date of Last Menstrual Period + 7 Days + 9 Calendar Months = Date of Estimated Date of Delivery

Example:
LMP = 8 May 2020

+1 year = 8 May 2021
−3 months = 8 February 2021
+7 days = 15 February 2021

280 days past the start of the last menstrual period is found by checking the day of the week of the LMP and adjusting the calculated date to land on the same day of the week. Using the example above, 8 May 2020 is a Friday. The calculated date (15 February) is a Monday; adjusting to the closest Friday produces 12 February, which is exactly 280 days past 8 May. The calculation method does not always result in 280 days because not all calendar months are the same length; it does not account for leap years.

Mobile apps

Mobile apps essentially always give consistent estimations compared to each other and correct for leap year, while pregnancy wheels made of paper can differ from each other by 7 days and generally do not correct for leap year. [15]

Other suggested durations

  • 276 days for both ultrasound-estimated and LMP-estimated gestational age in a US study of 1867 singleton live births. [11]
  • 281 days after LMP with a standard deviation of 13 days, was the result of a population-based study of 427,581 singleton births in Sweden. [16]
  • 281 days after LMP for first-time mothers and 280 days for all others were the medians found by a 1995 American study of 1,970 spontaneous births. Standard deviation was 7–9 days. [17] [18]
  • 282 days after LMP was recommended for cases where LMP is the only known factor, in a study of 17,450 patients combining LMP and ultrasound measurement techniques. [19]
  • A median of 288 days (274 days from the date of ovulation) for first-time mothers and 283 days (269 days from the date of ovulation) for mothers with at least one previous pregnancy was found by a 1990 study of 114 white, private-care patients with uncomplicated pregnancies and spontaneous labor. The authors suggest that excluding pregnancies involving complications (that often lead to pre-term deliveries) accounts for the longer periods. [20]

Individualized

  • Multiple linear regression models have also been developed that account for maternal parity, age, and race, all which have been found to be important variables determining the length of human gestation. Multiparous women, women aged less than 19 or more than 34 years, and black women have been found to have shorter gestations than primiparous women, women aged 19 to 34 years, or white women. [21]

Related Research Articles

<span class="mw-page-title-main">Multiple birth</span> End of a multiple pregnancy where two or more offspring are born

A multiple birth is the culmination of one multiple pregnancy, where in the mother gives birth to two or more babies. A term most applicable to vertebrate species, multiple births occur in most kinds of mammals, with varying frequencies. Such births are often named according to the number of offspring, as in twins and triplets. In non-humans, the whole group may also be referred to as a litter, and multiple births may be more common than single births. Multiple births in humans are the exception and can be exceptionally rare in the largest mammals.

<span class="mw-page-title-main">Ovulation</span> Release of egg cells from the ovaries

Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertilized by sperm. In addition, the uterine lining (endometrium) is thickened to be able to receive a fertilized egg. If no conception occurs, the uterine lining as well as the egg will be shed during menstruation.

<span class="mw-page-title-main">Obstetric ultrasonography</span> Use of medical ultrasonography in pregnancy

Obstetric ultrasonography, or prenatal ultrasound, is the use of medical ultrasonography in pregnancy, in which sound waves are used to create real-time visual images of the developing embryo or fetus in the uterus (womb). The procedure is a standard part of prenatal care in many countries, as it can provide a variety of information about the health of the mother, the timing and progress of the pregnancy, and the health and development of the embryo or fetus.

HELLP syndrome is a complication of pregnancy; the acronym stands for hemolysis, elevated liver enzymes, and low platelet count. It usually begins during the last three months of pregnancy or shortly after childbirth. Symptoms may include feeling tired, retaining fluid, headache, nausea, upper right abdominal pain, blurry vision, nosebleeds, and seizures. Complications may include disseminated intravascular coagulation, placental abruption, and kidney failure.

In obstetrics, gestational age is a measure of the age of a pregnancy taken from the beginning of the woman's last menstrual period (LMP), or the corresponding age of the gestation as estimated by a more accurate method, if available. Such methods include adding 14 days to a known duration since fertilization, or by obstetric ultrasonography. The popularity of using this measure of pregnancy is largely due to convenience: menstruation is usually noticed, while there is generally no convenient way to discern when fertilization or implantation occurred.

<span class="mw-page-title-main">Pregnancy</span> Time of offspring development in mothers body

Pregnancy is the time during which one or more offspring develops (gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins.

<span class="mw-page-title-main">Human fertilization</span> Union of a human egg and sperm

Human fertilization is the union of an egg and sperm, occurring primarily in the ampulla of the fallopian tube. The result of this union leads to the production of a fertilized egg called a zygote, initiating embryonic development. Scientists discovered the dynamics of human fertilization in the 19th century.

<span class="mw-page-title-main">Human reproduction</span> Procreative biological processes of humanity

Human reproduction is sexual reproduction that results in human fertilization to produce a human offspring. It typically involves sexual intercourse between a sexually mature human male and female. During sexual intercourse, the interaction between the male and female reproductive systems results in fertilization of the ovum by the sperm to form a zygote. While normal cells contain 46 chromosomes, gamete cells only contain 23 single chromosomes, and it is when these two cells merge into one zygote cell that genetic recombination occurs and the new zygote contains 23 chromosomes from each parent, giving it 46 chromosomes. The zygote then undergoes a defined development process that is known as human embryogenesis, and this starts the typical 9-month gestation period that is followed by childbirth. The fertilization of the ovum may be achieved by artificial insemination methods, which do not involve sexual intercourse. Assisted reproductive technology also exists.

Postterm pregnancy is when a woman has not yet delivered her baby after 42 weeks of gestation, two weeks beyond the typical 40-week duration of pregnancy. Postmature births carry risks for both the mother and the baby, including fetal malnutrition, meconium aspiration syndrome, and stillbirths. After the 42nd week of gestation, the placenta, which supplies the baby with nutrients and oxygen from the mother, starts aging and will eventually fail. Postterm pregnancy is a reason to induce labor.

<span class="mw-page-title-main">Fundal height</span>

Fundal height, or McDonald's rule, is a measure of the size of the uterus used to assess fetal growth and development during pregnancy. It is measured from the top of the mother's uterus to the top of the mother's pubic symphysis. Fundal height, when expressed in centimeters, roughly corresponds to gestational age in weeks between 16 and 36 weeks for a vertex fetus. When a tape measure is unavailable, finger widths are used to estimate centimeter (week) distances from a corresponding anatomical landmark. However, landmark distances from the pubic symphysis are highly variable depending on body type. In clinical practice, recording the actual fundal height measurement from the palpable top of the uterus to the superior edge of the pubic symphysis is standard practice beginning around 20 weeks gestation.

Caesarean delivery on maternal request (CDMR) is a caesarean section birth requested by the pregnant woman without a medical reason.

<span class="mw-page-title-main">Vasa praevia</span> Condition in which fetal blood vessels cross or run near the internal opening of the uterus

Vasa praevia is a condition in which fetal blood vessels cross or run near the internal opening of the uterus. These vessels are at risk of rupture when the supporting membranes rupture, as they are unsupported by the umbilical cord or placental tissue.

<span class="mw-page-title-main">Crown-rump length</span> Ultrasound measurement of a foetus

Crown-rump length (CRL) is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump). It is typically determined from ultrasound imagery and can be used to estimate gestational age.

Pregnancy rate is the success rate for getting pregnant. It is the percentage of all attempts that leads to pregnancy, with attempts generally referring to menstrual cycles where insemination or any artificial equivalent is used, which may be simple artificial insemination (AI) or AI with additional in vitro fertilization (IVF).

<span class="mw-page-title-main">Cephalic presentation</span> Medical condition

A cephalic presentation or head presentation or head-first presentation is a situation at childbirth where the fetus is in a longitudinal lie and the head enters the pelvis first; the most common form of cephalic presentation is the vertex presentation, where the occiput is the leading part. All other presentations are abnormal (malpresentations) and are either more difficult to deliver or not deliverable by natural means.

<span class="mw-page-title-main">Monoamniotic twins</span> Identical twins sharing the same amniotic sac in the womb

Monoamniotic twins are identical or semi-identical twins that share the same amniotic sac within their mother's uterus. Monoamniotic twins are always monochorionic and are usually termed Monoamniotic-Monochorionic twins. They share the placenta, but have two separate umbilical cords. Monoamniotic twins develop when an embryo does not split until after formation of the amniotic sac, at about 9–13 days after fertilization. Monoamniotic triplets or other monoamniotic multiples are possible, but extremely rare. Other obscure possibilities include multiples sets where monoamniotic twins are part of a larger gestation such as triplets, quadruplets, or more.

Sex after pregnancy is often delayed for several weeks or months, and may be difficult and painful for women. Painful intercourse is the most common sexual activity-related complication after childbirth. Since there are no guidelines on resuming sexual intercourse after childbirth, the postpartum patients are generally advised to resume sex when they feel comfortable to do so. Injury to the perineum or surgical cuts (episiotomy) to the vagina during childbirth can cause sexual dysfunction. Sexual activity in the postpartum period other than sexual intercourse is possible sooner, but some women experience a prolonged loss of sexual desire after giving birth, which may be associated with postnatal depression. Common issues that may last more than a year after birth are greater desire by the man than the woman, and a worsening of the woman's body image.

The following outline is provided as an overview of and topical guide to obstetrics:

Post-maturity syndrome refers to the condition of a baby born after a post-term pregnancy, first described by Stewart H. Clifford in 1954. Post-maturity refers to any baby born after 42 weeks gestation, or 294 days past the first day of the mother's last menstrual period. Less than 6 percent of all babies are born after this time. The syndrome develops in about 20% of human pregnancies continuing past the expected delivery date.

<span class="mw-page-title-main">Cervical pregnancy</span> Medical condition

A cervical pregnancy is an ectopic pregnancy that has implanted in the uterine endocervix. Such a pregnancy typically aborts within the first trimester, however, if it is implanted closer to the uterine cavity – a so-called cervico-isthmic pregnancy – it may continue longer. Placental removal in a cervical pregnancy may result in major hemorrhage.

References

  1. ↑ A Concise Guide to the Employment Ordinance. Labour Department, Hong Kong Government
  2. ↑ "Definition of Estimated date of confinement (EDC)". MedicineNet, Inc. Archived from the original on 11 August 2020. Retrieved 13 January 2010.
  3. ↑ Durham, Janelle (2004). "How accurate is your Due Date?". www.transitiontoparenthood.com. Archived from the original on 24 December 2010. Retrieved 13 January 2010.
  4. ↑ "How accurate are 'due dates'?". BBC News. 2015-02-03. Retrieved 2021-07-30.
  5. ↑ "Childbirth in Medieval and Tudor Times". The Tudor Society. 27 August 2015. Retrieved 31 December 2017.
  6. ↑ "What is full-term?". www.marchofdimes.org. Retrieved 2023-08-03.
  7. 1 2 Obstetric Data Definitions Issues and Rationale for Change - Gestational Age & Term Archived 2013-11-06 at the Wayback Machine from Patient Safety and Quality Improvement at American Congress of Obstetricians and Gynecologists. Created November 2012.
  8. ↑ Tunon, K.; Eik-Nes, S. H.; Grøttum, P.; Von Düring, V.; Kahn, J. A. (2000). "Gestational age in pregnancies conceived after in vitro fertilization: A comparison between age assessed from oocyte retrieval, crown-rump length and biparietal diameter". Ultrasound in Obstetrics and Gynecology. 15 (1): 41–46. doi: 10.1046/j.1469-0705.2000.00004.x . PMID   10776011.
  9. ↑ "Methods for Estimating the Due Date". www.acog.org. Retrieved 2021-07-30.
  10. ↑ Morgan, John A.; Cooper, Danielle B. (2021), "Pregnancy Dating", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   28723047 , retrieved 2021-07-30
  11. 1 2 3 Hoffman, Caroline S.; Messer, Lynne C.; Mendola, Pauline; Savitz, David A.; Herring, Amy H.; Hartmann, Katherine E. (2008). "Comparison of gestational age at birth based on last menstrual period and ultrasound during the first trimester". Paediatric and Perinatal Epidemiology. 22 (6): 587–596. doi:10.1111/j.1365-3016.2008.00965.x. ISSN   0269-5022. PMID   19000297.
  12. ↑ Evaluation of Gestation at eMedicine
  13. ↑ Edwards, Kenia I.; Itzhak, Petr (2020), "Estimated Date of Delivery", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   30725671 , retrieved 2020-10-30
  14. ↑ "Calculating a Due Date" . Retrieved 2021-07-30.
  15. ↑ Chambliss LR, Clark SL (2014). "Paper gestational age wheels are generally inaccurate". Am. J. Obstet. Gynecol. 210 (2): 145.e1–4. doi:10.1016/j.ajog.2013.09.013. PMID   24036402.
  16. ↑ Bergsjø P, Denman DW 3rd, Hoffman HJ, Meirik O. (1990). "Duration of human singleton pregnancy. A population-based study". Acta Obstet Gynecol Scand. 69 (3): 197–207. doi:10.3109/00016349009028681. PMID   2220340. S2CID   21358120.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  17. ↑ Gray, H (1962). "Duration of pregnancy". Stanford Medical Bulletin. 20: 24–8. PMID   13901307.
  18. ↑ H. Kieler; O. Axelsson; S. Nilsson; U. Waldenströ (1995). "The length of human pregnancy as calculated by ultrasonographic measurement of the fetal biparietal diameter". Ultrasound in Obstetrics & Gynecology. 6 (5): 353–357. doi: 10.1046/j.1469-0705.1995.06050353.x . PMID   8590208. S2CID   39447672.
  19. ↑ Nguyen T, Larsen T, Engholm G, Møller H (1999). "Evaluation of ultrasound-estimated date of delivery in 17,450 spontaneous singleton births: do we need to modify Naegele's rule?". Ultrasound Obstet Gynecol. 14 (1): 23–8. doi: 10.1046/j.1469-0705.1999.14010023.x . PMID   10461334.
  20. ↑ Mittendorf R, Williams MA, Berkey CS, Cotter PF (1990). "The length of uncomplicated human gestation". Obstet Gynecol. 75 (5): 929–32. PMID   2342739.
  21. ↑ Mittendorf R, Williams MA, Berkey CS, Lieberman E, Monson RR (1993). "Predictors of human gestational length". American Journal of Obstetrics and Gynecology. 168 (2): 480–484. doi:10.1016/0002-9378(93)90476-Y. PMID   8438913.
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