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Obstetrics
Placental weight and birthweight: does the association differ between pregnancies with and without preeclampsia?

https://doi.org/10.1016/j.ajog.2009.06.003Get rights and content

Objective

Placental weight and infant birthweight may be markers of different types of preeclampsia. We studied birthweight within placental weight percentiles in pregnancies with and without preeclampsia.

Study Design

This was a population study of 317,688 singleton births.

Results

Within the lowest 10% of placental weight, 36% of the offspring were small for gestational age (SGA) in preeclamptic pregnancies and 14% in normotensive pregnancies (relative risk, 2.6; 95% confidence interval, 2.4–2.8). Risk of SGA subsided with increasing placental weight and was negligible at >50th percentile. At low placental weights, large for gestational age (LGA) offspring were nearly nonexistent; however, at >70th percentile, LGA occurred more often in pregnancies with preeclampsia. Within the highest 10% of placental weight, 20.7% of the infants were LGA in the preeclampsia group, and 15.3% of the infants were LGA in pregnancies without preeclampsia (relative risk, 1.4; 95% confidence interval, 1.2–1.5).

Conclusion

In pregnancies with small placentas, the offspring were more often SGA in preeclamptic pregnancies and more often LGA at high placental weights. The results support the hypothesis that preeclampsia may represent different diseases, depending on placental size and infant birthweight.

Section snippets

Materials and Methods

The study population included all pregnancies in Norway during a 6-year period, 1999-2004 (n = 333,984 pregnancies). Data were derived from the Medical Birth Registry of Norway that is based on compulsory notification of each birth with delivery after 16 weeks of gestation in Norway.8 The notification form is completed by the attending midwife or doctor shortly after delivery. We restricted the study to singleton pregnancies, with recorded offspring birthweight between 250 and 6500 g, recorded

Results

A total of 12,813 women (4.0%) were diagnosed with preeclampsia. Among all deliveries, 7943 children were in the lowest 2.5 percentile of birthweight and therefore defined as SGA, and 7942 children were in the highest 2.5 percentile of birthweight and defined as LGA. In the preeclampsia group, 8.1% were SGA, compared with 2.3% of the offspring of pregnancies without preeclampsia. In the preeclampsia group, 3.4% were LGA, compared with 2.3% in pregnancies without preeclampsia.

Within each 10th

Comment

This population study of >300,000 singleton births shows that, at low placental weights, the risk of SGA offspring was generally high, but nearly 3 times higher in preeclamptic pregnancies, compared with pregnancies without preeclampsia. At high placental weights, the risk of LGA offspring was higher in the preeclampsia group, but this difference was attenuated partly after taking maternal diabetes mellitus into account. Mean offspring birthweight was substantially lower in the preeclampsia

Acknowledgments

We thank the women who provided the information and the Medical Birth Registry of Norway for the use of these data.

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  • Cited by (0)

    This study was supported by the University of Oslo and by the Norwegian University of Science and Technology.

    Cite this article as: Eskild A, Romundstad PR, Vatten LJ. Placental weight and birthweight: does the association differ between pregnancies with and without preeclampsia? Am J Obstet Gynecol 2009;201:595.e1-5.

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