Publication:

An observational study to determine accuracy of various methods used to assign gestational age and correlate with outcome

Background Appropriate estimation of gestational age is paramount in obstetric care. Uncertain gestational age may lead to adverse pregnancy outcome like low birth weight, spontaneous or iatrogenic preterm delivery and perinatal mortality independent of maternal characteristics. In India, seeking of early medical attention in pregnancy is still not the norm. Three methods to estimate the estimated date of delivery are available, namely, menstrual history, clinical examination and by ultrasound.  This study attempts to analyse the accuracy of the three methods used and their correlation with maternal and fetal outcome.

Methods 260 patients presenting to the outpatient department were enrolled irrespective of the gestational age but as soon as they got registered. Ultrasonography was advised if the patient did not have one. EDD was calculated by various methods and was recorded. If significant discrepancy existed, EDD was reassigned. Patients were followed up till the time of their delivery. After the delivery of the baby gestational age was assessed by the neonatologist and was compared with the gestational age at the time of delivery by the three methods. Maternal and fetal outcomes were compared in the form of avoided inductions and maturity of the baby at the time of delivery by all the three methods.

Results The kappa coefficient for the agreement between dating by ultrasound scan and neonatologist was 0.415 whereas for menstrual dates and clinical examination it was 0.197 and 0.369 respectively thus it can be interpreted that the accuracy of ultrasonography may be slightly better than menstrual dates and clinical examination. 75 patients required reassigning of EDD, Induction of labor for supposed post-term pregnancy was avoided in 13% of the patients.

Conclusions Ultrasonography was found to be accurate for determination of term /preterm/ post-term births followed by clinical examination and then the menstrual EDD. Induction of labor for supposed post-term pregnancy was avoided in 13% of the patients in whom EDD was ”assigned” thus stressing that EDD should be reassigned when there is discrepancy between menstrual EDD, Ultrasonography EDD and EDD by clinical examination.