Accuracy of ultrasound dating scan

The primary outcome measure was willingness to accept induction of labor at an LMP-derived gestational age of 40 weeks plus 10 days when late pregnancy ultrasound scan-derived gestational age was less than 40 weeks plus 10 days.

How is an ultrasound performed?

The first trimester was defined as a gestational age of 1—13 weeks, the second trimester as 14—27 weeks, and the third trimester as 28—42 weeks. Further, the early second trimester was defined as a gestational age of 15—22 weeks and the late second trimester as 23—27 weeks. Frequency tables were generated for relevant variables.

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A P -value of less than 0. A total of questionnaires were administered, but only were completed correctly, giving a response rate of The mean age of the respondents was Most of the women Four hundred and thirty-one respondents The majority of respondents were multiparous Further details of the sociodemographic characteristics of the respondents are shown in Table 1.

The mean gestational age at recruitment and antenatal booking for respondents was One hundred and sixty-seven One hundred and ninety-one The remaining eight women 1. On the other hand, All the women who responded positively Likewise, all the women who responded negatively Characteristics of respondents versus acceptance of labor induction for postdatism using menstrual dating. OR, odds ratio; CI, confidence interval. This study demonstrates that pregnant women in Enugu, Nigeria, have poor knowledge of the limits of accuracy of late pregnancy ultrasound scan in estimating the delivery date.

This poor knowledge invariably translated into the observed perception of respondents toward induction of labor for postdatism, as more than half of the women This attitude poses a great challenge to perinatal care in our environment because an ultrasound scan is usually carried out in the third trimester when the margin of error is up to 3 weeks. Late booking for antenatal care might have strongly contributed to the poor uptake 7. The recent proliferation of ultrasound scan services in our environment came with a wave of optimism that ultrasound scanning could accurately determine all aspects of fetal well-being, hence only the well-educated or informed could question or resist its results.

This misconception is further worsened by uncontrolled purchasing and use of ultrasound scanning machines by poorly trained personnel who advertise themselves as sonologists or sonographers.

What is even more worrisome is the increasing number of self-referrals for ultrasound by our pregnant women merely to know the EDD which they usually hold on to. Legislation to regulate the acquisition and use of ultrasound by health professionals in the country may help to keep this problem in check. Such legislation should also discourage self-referral by pregnant women for ultrasound. This will further help to prevent our women from visiting poorly trained sonologists and guard against the possible effects of unreliable ultrasound scan results on maternal and neonatal health.

Tertiary education was identified in this report as a strong determinant of acceptance of induction of labor for postdatism using the last menstrual date. This may be explained by the expected impact of education on uptake of maternal and neonatal health services, as observed by previous authors. Also, the lesser educated are more likely to rely more on the impression created outside about a procedure like ultrasound, whether right or wrong.

As pointed out by Olusanya et al, 12 the higher the educational status of the woman, the higher the social class, and this no doubt may explain the higher acceptance rate among women of higher social class than among women of lower social class. This will help to reduce the incidence of prolonged pregnancy and its complications in our environment.

The limitation of this study is that the willingness to accept labor induction was assumed to mean acceptance of induction of labor. It is likely that some of the respondents might have responded differently if their pregnancies were actually prolonged. However, the effect of this limitation on the study estimates is likely to be minimal. MFM mums share their stories plus expert sonographers explain why it happens and what to do if you're told your due dates are wrong.

Women's Health Care Physicians

Original date given was 18 December but at the scan it was moved to 31 Dec. It just doesn't quite add up by my reckoning of when I think I ovulated and when I know we did the deed! Unless you have an early pregnancy scan most of you will be given your estimated due date at the week scan. Of course you have probably already used an online due date calculator. This is where you discover that your due date isn't based on the date you conceived, it's actually calculated from when your last menstrual period started your LMP.

It's because it gives a definite date for health professionals to work with. There would be so many variables if it was calculated from when you think you conceived, especially as everyone's cycles are different and the fact that you don't necessarily conceive on the day you have sex!

But this will only give you a rough idea. This is especially true if you have an irregular cycle or have been on the Pill for example. Experts say that the scan date can sometimes come out as less pregnant than suggested by your LMP. But then again with my first baby I was spot on with dates, he always measured big and he was a week overdue Babies are ready when they're ready - try not to worry easier said than done. But Nigel also says that the estimated and that is all it is date is normally accurate plus or minus about a week.

The healthcare professionals will stick to this date as far as possible because it is then used as the baseline for growth throughout pregnancy. Your baby's growth can slow down and then have spurts. I've not even had my 20 week scan yet. I have scans every few weeks so it will probably keep on changing. American College of Obstetricians and Gynecologists. Women's Health Care Physicians.

Recommendations The American College of Obstetricians and Gynecologists, the American Institute of Ultrasound in Medicine, and the Society for Maternal—Fetal Medicine make the following recommendations regarding the method for estimating gestational age and due date: As soon as data from the last menstrual period LMP , the first accurate ultrasound examination, or both are obtained, the gestational age and the EDD should be determined, discussed with the patient, and documented clearly in the medical record.

Introduction An accurately assigned EDD early in prenatal care is among the most important results of evaluation and history taking.

Predicting delivery date by ultrasound and last menstrual period in early gestation.

Clinical Considerations in the Second Trimester Using a single ultrasound examination in the second trimester to assist in determining the gestational age enables simultaneous fetal anatomic evaluation. Ultrasonography dating in the second trimester typically is based on regression formulas that incorporate variables such as the biparietal diameter and head circumference measured in transverse section of the head at the level of the thalami and cavum septi pellucidi; the cerebellar hemispheres should not be visible in this scanning plane the femur length measured with full length of the bone perpendicular to the ultrasound beam, excluding the distal femoral epiphysis the abdominal circumference measured in symmetrical, transverse round section at the skin line, with visualization of the vertebrae and in a plane with visualization of the stomach, umbilical vein, and portal sinus 8 Other biometric variables, such as additional long bones and the transverse cerebellar diameter, also can play a role.

Conclusion Accurate dating of pregnancy is important to improve outcomes and is a research and public health imperative. Fetal Imaging Workshop Invited Participants.


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A comparison of recalled date of last menstrual period with prospectively recorded dates. J Womens Health Larchmt ; Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination. Am J Obstet Gynecol ; Last menstrual period versus ultrasound for pregnancy dating.

Int J Gynaecol Obstet ; First trimester ultrasound screening is effective in reducing postterm labor induction rates: Ultrasound for fetal assessment in early pregnancy. Cochrane Database of Systematic Reviews , Issue 7. Predicting delivery date by ultrasound and last menstrual period in early gestation. New charts for ultrasound dating of pregnancy and assessment of fetal growth: Ultrasound Obstet Gynecol ; First- and second-trimester ultrasound assessment of gestational age.

First- vs second-trimester ultrasound: Br J Obstet Gynaecol ; Gestational age in pregnancies conceived after in vitro fertilization: Ultrasound dating at 12—14 weeks of gestation. A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies.