Gestational age in pregnancies conceived after in vitro fertilization: a comparison between age assessed from oocyte retrieval, crown-rump length and biparietal diameter.

OBJECTIVE: To compare gestational age (GA) and day of delivery estimated from the time of in vitro fertilization (IVF) (oocyte retrieval + 14 days), the ultrasonic measurement of the crown-rump length (CRL) and the biparietal diameter (BPD) in pregnancies conceived in an IVF setting. DESIGN: Included were 208 singletons and 72 twin pregnancies conceived after IVF. GA estimated from the time of IVF was compared with the GA estimated from the ultrasonic measurement of the CRL in the first trimester and the BPD in the second trimester. RESULTS: In singletons the mean difference in gestational age was 0.9 days between IVF and CRL estimates and 2.1 days between IVF and BPD estimates. The gestational age as estimated from CRL or BPD was shorter than the GA estimated from IVF. There was no systematic variation in the mean differences in GA between the methods. In three pregnancies there was a difference of more than 7 days between the gestational age estimated from IVF and CRL and in 22 pregnancies between gestational age estimated from IVF and BPD. A difference of > 14 days for any of the estimates was not found in any case. In singletons there was a high correlation in the gestational age at birth assessed from the time of IVF and from CRL, from the time of IVF and from BPD. CONCLUSION: Assessment of gestational age from the time of IVF, CRL and BPD in pregnancies conceived after IVF shows equally high agreement between the three methods. This supports the use of ultrasound as a reliable method for estimation of gestational age.

Fetal outcome in pregnancies defined as post-term according to the last menstrual period estimate, but not according to the ultrasound estimate.

OBJECTIVE: To study the risk of adverse fetal outcome in fetuses that were post-term according to the last menstrual period estimate but not according to the ultrasound estimate. DESIGN: A total of 11,510 women with singleton pregnancies, reliable last menstrual period and delivery after 37 weeks were divided into four groups: women who delivered at term, i.e. within 259-295 days according to both the ultrasound and the last menstrual period estimate; women who delivered post-term according to the last menstrual period estimate but not according to the ultrasound estimate; women who delivered post-term according to the ultrasound estimate but not according to the last menstrual period estimate; and women who delivered post-term according to both the ultrasound and the last menstrual period estimates. Stepwise logistic regression was used to test whether the risk of Apgar score of < 7 after 5 min and transfer to the neonatal intensive care unit increased in any of the post-term groups. RESULTS: There was no significant difference in mortality between the term group and the three study groups. There was no significant increase in the risk for Apgar score of < 7 after 5 min or transfer to the neonatal intensive care unit for pregnancies that were defined as post-term according to the last menstrual period estimate but not according to the ultrasound estimate. There was, however, an increased risk for Apgar score of < 7 after 5 min in the group that was post-term according to the ultrasound estimate but not according to the last menstrual period estimate. There was also an increased risk for transfer to the neonatal intensive care unit in the group that was post-term according to both estimates. CONCLUSION: The effect of ultrasound in changing the estimated day of delivery to a later date leading to pregnancies becoming post-term according to the last menstrual period estimate but not according to the ultrasound estimate does not have any adverse consequences for the fetal outcome. However, there seems to be an increased risk for adverse consequences for pregnancies that are post-term according to the ultrasound estimate.

Fetal outcome when the ultrasound estimate of the day of delivery is more than 14 days later than the last menstrual period estimate.

OBJECTIVE: To evaluate the effect on fetal outcome of changing the estimated day of delivery as calculated according to ultrasound measurements more than 14 days later than the day estimated according to the last menstrual period. DESIGN: A non-selected population comprising 15,241 women was evaluated. A study group (the day of delivery based on the ultrasound estimate being changed to more than 14 days later than the estimate based on the last menstrual period) and a control group (the two estimates being within 7 days of each other) were compared regarding various parameters concerning fetal outcome. RESULTS: Changing the estimated day of delivery, based on the ultrasound evaluation, to a date 14 days later than the day of delivery as estimated according to the last menstrual period did not influence the risk of abortion, perinatal death or transferral to the neonatal intensive care unit. There was a difference of 3 days in the accuracy of the prediction of day of delivery between the two groups. There was a greater number of infants with a birth weight below 2500 g in the study group, but no difference was found between the groups in the number of infants with a birth weight < 2 SD from the mean according to the ultrasound estimate. CONCLUSION: There was no indication of any adverse consequence of the routine scan and change of estimated day of delivery among 15,000 pregnancies in a non-selected population.

The impact of fetal, maternal and external factors on prediction of the day of delivery by the use of ultrasound.

In a non-selected population comprising 15,241 women, an evaluation was performed of the impact of fetal, maternal and external factors on the ultrasonic measurement of the biparietal diameter (BPD) and the day of delivery. The 7824 women who constituted the study population had singleton pregnancies and reliable menstrual histories, and they delivered spontaneously after 37 weeks. Multiple linear regression analysis was used. There was a difference in the size of the BPD at the ultrasound scan related to the gender, parity, maternal age, gestational age according to the last menstrual period and the experience of the operators. There was a total difference of +/- 1 day in the day of delivery as determined by ultrasound and the factors above. The effect on the day of delivery is explained by the differences in the BPD. An effect of gender on gestational length was present as well, which partly compensated for the difference in the BPD. In conclusion the accuracy of prediction of the day of delivery by ultrasound is influenced by the gender, parity, maternal age and the experience of the operator, but these differences are small and of no clinical importance.

A comparison between ultrasound and a reliable last menstrual period as predictors of the day of delivery in 15,000 examinations.

In a non-selected population comprising 15,241 women, an evaluation was performed of the ultrasonic measurement of the biparietal diameter compared with a reliable last menstrual period as the basis for estimation of the day of delivery. In women with a reliable menstrual history and spontaneous onset of labor, the ultrasound estimate was the significantly better predictor of the day of delivery in 52% of cases, and the last menstrual period estimate was the better predictor in 46% of cases. The percentages of women who delivered within 7 days of the predicted day were 61 and 56% for the ultrasound and the last menstrual period estimations, respectively. There was a significantly narrower distribution of births according to the ultrasound estimate (p < 0.001). The proportion of estimated postterm births was 4% using the ultrasound method and 10% using the last menstrual period method (p < 0.001). Even when the difference between the methods in predicting the day of delivery was less than 7 days, the ultrasound method was better than the last menstrual period method. It is concluded that ultrasonic measurement of the biparietal diameter between 15 and 22 weeks of pregnancy is the best method for the estimation of the day of delivery and should be used as a routine procedure.