Relationship between glomerular filtration rate (GFR in pregnancy and birth weight, estimated in three studies.

aGFRratio is the ratio of subject i’s GFR to the mean GFR. We used this metric to compare results across studies to adjust for differences in gestational week when GFR was measured.bPartial r is partial correlation coefficient.cmeasured GFR using inulin clearance.dThe beta and partial r for Gibson and Dunlop studies were calculated conditional on gestational age at birth, using the raw data in the original publications.eGibson had three SGA infants; their inclusion probably accounts for why that study had sufficient power to detect a birth weight-GFR relationship.fThe subjects in the Dunlop study had a narrow range of birth weights, and that may explain why the standard error is relatively large in that analysis.gTaking the intraclass correlation coefficient (ICC) for creatinine into account gives a corrected β (SE) for the CG formula of 155 (75) (see text).