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Ultrasound Obstet Gynecol. 2000 Jan;15(1):41-6.

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

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Department of Obstetrics and Gynecology, University Hospital of Trondheim, Norway.



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.


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.


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.


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.

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