First trimester dating guidelines

How accurate is sonographic dating in the first trimester?

Overall, the accuracy of sonographic dating in the first trimester is ~5 days (95% confidence range). History and etymology

What is the first trimester of pregnancy?

‘First trimester’ here refers to a stage of pregnancy starting from the time at which viability can be confirmed (i.e. presence of a gestational sac in the uterine cavity with an embryo demonstrating cardiac activity) up to 13 + 6 weeks of gestation. Ultrasound scans performed after this gestational age are not considered in these Guidelines.

What is the most reliable method to establish pregnancy dating?

Ultrasound is the most reliable method to establish pregnancy dating, particularly first-trimester ultrasound[1]. Transvaginal ultrasound utilizes 6 MHz to 10 MHz ultrasound probe.

How is Naegeles rule used to establish pregnancy dating?

When using the patients last menstrual period to establish pregnancy dating, Naegeles rule requires the use of a calendar[1].  Ultrasound is the most reliable method to establish pregnancy dating, particularly first-trimester ultrasound[1]. Transvaginal ultrasound utilizes 6 MHz to 10 MHz ultrasound probe.

How accurate is dating by first trimester ultrasound?

Basically Dating by first trimester ultrasound, via the crown-rump length, has a 95% confidence range of ±5 days, slightly better than the ±8 days for dating by second trimester ultrasound at 14–20 weeks. This small difference appears to be too small to justify a routine first trimester scan for the purpose of dating the pregnancy.

How accurate are ultrasounds in Predicting gender?

While sonographers who perform high volumes of obstetric ultrasounds are very accurate in providing gender predictions in the second and third trimesters of pregnancy, lower accuracy rates are obtained in the first trimester.

How successful is sonographic gender determination in the first trimester?

Conclusions: Sonographic gender determination provides high success rates in the first trimester. Results vary depending on sonographer experience, fetal age and fetal gender. Practice guidelines regarding gender disclosure should be developed. Predictions prior to 12 weeks should be discouraged.

How accurate are sonographers at predicting fetal fetal scans?

It is also important to note that sonographers in this study were completing high volumes of early fetal scans, and as a result, may be more confident in making predictions than those seeing few obstetric patients. Further study opportunities exist to examine the impact of experience levels and sonographer accuracy rates.

What is Naegele’s rule for due date?

Naegele’s rule, derived from a German obstetrician, subtracts 3 months and adds 7 days to calculate the estimated due date (EDD). It is prudent for the obstetrician to get a detailed menstrual history, including duration, flow, previous menstrual periods, and hormonal contraceptives.

Does Naegeles rule apply to the length of pregnancy?

Naegeles rule and the length of pregnancy - A review Naegeles rule should be considered as a guideline for the expected date of confinement, and not a definite date. Naegeles rule should be considered as a guideline for the expected date of confinement, and not a definite date. Naegeles rule and the length of pregnancy - A review

How does the Naegeles rule calculator work?

The Naegeles Rule Calculator calculates the due date of a womans pregnancy based on the first day of the last menstrual cycle that a woman had. Based on the first day of the last menstrual cycle a woman has had, the due date for the pregnancy is predicted by adding 9 months to the date plus 7 days.

Is the Naegele rule for estimating the date of delivery misinterpreted?

Recent literature suggests that Franz Carl Naegeles (1778-1851) rule for estimating the date of delivery has been misinterpreted, resulting in this being brought forward by five days. Baskett and Nageles work underpinning this argument has become widely accepted and quoted in obstetrical and midwifery textbooks.