Table 2. Serum Creatinine Medians by Gestational Age Group and Day of Life (Days 1-28) 	
Day of Life	N Infants	Median SCr, mg/dL (IQR)	95% BCa CI	
22-24 weeks	
1	4	—	—	
2	323	0.79 (0.70-0.90)	[0.75-0.80]	
3	382	0.90 (0.80-1.03)	[0.86-0.90]	
4	380	0.93 (0.80-1.10)	[0.90-0.95]	
5	377	0.90 (0.79-1.10)	[0.89-0.93]	
6	389	0.90 (0.76-1.10)	[0.87-0.91]	
7	397	0.90 (0.74-1.08)	[0.86-0.90]	
8	419	0.86 (0.70-1.02)	[0.82-0.88]	
9	439	0.83 (0.68-1.01)	[0.80-0.84]	
10	462	0.80 (0.65-0.98)	[0.76-0.80]	
11	461	0.77 (0.62-1.00)	[0.73-0.80]	
12	487	0.78 (0.62-1.00)	[0.74-0.80]	
13	469	0.76 (0.60-0.96)	[0.72-0.80]	
14	463	0.72 (0.57-0.99)	[0.70-0.75]	
15	470	0.71 (0.58-0.97)	[0.69-0.76]	
16	487	0.72 (0.57-0.97)	[0.69-0.76]	
17	441	0.70 (0.56-0.92)	[0.64-0.70]	
18	474	0.70 (0.55-0.90)	[0.66-0.70]	
19	445	0.70 (0.54-0.90)	[0.66-0.71]	
20	422	0.68 (0.55-0.90)	[0.64-0.70]	
21	460	0.64 (0.50-0.85)	[0.60-0.68]	
22	451	0.62 (0.50-0.87)	[0.59-0.64]	
23	441	0.63 (0.50-0.84)	[0.60-0.65]	
24	443	0.61 (0.48-0.77)	[0.60-0.63]	
25	460	0.60 (0.48-0.80)	[0.56-0.60]	
26	436	0.58 (0.45-0.80)	[0.54-0.60]	
27	444	0.59 (0.43-0.78)	[0.55-0.60]	
28	427	0.55 (0.41-0.80)	[0.51-0.58]	
25-27 weeks	
1	3	—	—	
2	528	0.80 (0.72-0.93)	[0.80-0.82]	
3	663	0.89 (0.78-1.01)	[0.86-0.90]	
4	688	0.85 (0.72-1.00)	[0.81-0.86]	
5	685	0.83 (0.70-0.99)	[0.80-0.85]	
6	711	0.80 (0.67-0.97)	[0.78-0.80]	
7	717	0.78 (0.65-0.94)	[0.75-0.80]	
8	703	0.74 (0.60-0.90)	[0.71-0.75]	
9	692	0.70 (0.57-0.86)	[0.65-0.70]	
10	676	0.67 (0.54-0.82)	[0.64-0.69]	
11	652	0.65 (0.51-0.80)	[0.61-0.66]	
12	624	0.64 (0.50-0.80)	[0.61-0.65]	
13	610	0.60 (0.50-0.80)	[0.59-0.59]	
14	583	0.60 (0.48-0.74)	[0.57-0.60]	
15	577	0.60 (0.49-0.77)	[0.57-0.60]	
16	597	0.60 (0.48-0.76)	[0.56-0.60]	
17	581	0.57 (0.44-0.74)	[0.54-0.60]	
18	581	0.56 (0.44-0.71)	[0.52-0.58]	
19	588	0.57 (0.46-0.71)	[0.54-0.59]	
20	543	0.57 (0.45-0.71)	[0.54-0.59]	
21	551	0.51 (0.41-0.68)	[0.50-0.52]	
22	539	0.51 (0.41-0.67)	[0.50-0.51]	
23	543	0.51 (0.42-0.68)	[0.50-0.53]	
24	548	0.50 (0.40-0.64)	[0.47-0.50]	
25	533	0.50 (0.40-0.60)	[0.48-0.50]	
26	537	0.49 (0.40-0.60)	[0.46-0.50]	
27	506	0.47 (0.39-0.60)	[0.44-0.48]	
28	492	0.45 (0.35-0.56)	[0.42-0.47]	
28-30 weeks	
1	3	—	—	
2	600	0.83 (0.75-0.95)	[0.80-0.84]	
3	794	0.85 (0.73-0.99)	[0.83-0.86]	
4	808	0.78 (0.66-0.90)	[0.75-0.79]	
5	812	0.72 (0.60-0.88)	[0.70-0.73]	
6	761	0.70 (0.60-0.81)	[0.68-0.69]	
7	691	0.69 (0.57-0.80)	[0.66-0.70]	
8	663	0.64 (0.52-0.76)	[0.62-0.66]	
9	564	0.61 (0.50-0.76)	[0.60-0.63]	
10	551	0.60 (0.50-0.72)	[0.57-0.60]	
11	507	0.55 (0.44-0.68)	[0.52-0.57]	
12	494	0.52 (0.44-0.65)	[0.50-0.54]	
13	430	0.52 (0.43-0.66)	[0.50-0.52]	
14	452	0.51 (0.41-0.65)	[0.50-0.53]	
15	422	0.50 (0.40-0.61)	[0.48-0.50]	
16	389	0.50 (0.40-0.61)	[0.47-0.50]	
17	426	0.50 (0.40-0.60)	[0.47-0.50]	
18	372	0.46 (0.39-0.59)	[0.42-0.47]	
19	377	0.48 (0.40-0.59)	[0.45-0.49]	
20	339	0.45 (0.38-0.56)	[0.43-0.47]	
21	348	0.46 (0.37-0.55)	[0.43-0.47]	
22	344	0.43 (0.34-0.52)	[0.41-0.43]	
23	334	0.43 (0.37-0.50)	[0.40-0.43]	
24	335	0.42 (0.35-0.51)	[0.40-0.43]	
25	304	0.40 (0.32-0.50)	[0.37-0.38]	
26	318	0.40 (0.33-0.48)	[0.39-0.39]	
27	312	0.39 (0.31-0.48)	[0.36-0.40]	
28	312	0.39 (0.31-0.47)	[0.37-0.40]	
31-33 weeks	
1	12	—	—	
2	986	0.82 (0.72-0.95)	[0.80-0.83]	
3	1324	0.80 (0.69-0.93)	[0.79-0.80]	
4	1286	0.71 (0.60-0.85)	[0.70-0.73]	
5	1167	0.65 (0.54-0.77)	[0.63-0.67]	
6	1025	0.60 (0.50-0.73)	[0.60-0.62]	
7	925	0.59 (0.48-0.71)	[0.57-0.60]	
8	778	0.56 (0.45-0.70)	[0.54-0.58]	
9	665	0.54 (0.44-0.67)	[0.52-0.55]	
10	611	0.53 (0.41-0.68)	[0.50-0.54]	
11	575	0.50 (0.40-0.62)	[0.49-0.49]	
12	547	0.50 (0.40-0.62)	[0.48-0.50]	
13	512	0.49 (0.40-0.60)	[0.47-0.50]	
14	475	0.47 (0.38-0.59)	[0.45-0.48]	
15	489	0.46 (0.37-0.58)	[0.43-0.47]	
16	427	0.46 (0.36-0.58)	[0.43-0.46]	
17	419	0.43 (0.35-0.55)	[0.40-0.43]	
18	427	0.41 (0.33-0.52)	[0.40-0.42]	
19	348	0.40 (0.32-0.52)	[0.37-0.40]	
20	355	0.40 (0.32-0.50)	[0.37-0.40]	
21	377	0.40 (0.30-0.49)	[0.37-0.40]	
22	338	0.38 (0.30-0.50)	[0.36-0.40]	
23	310	0.39 (0.30-0.48)	[0.36-0.40]	
24	348	0.37 (0.30-0.47)	[0.34-0.38]	
25	332	0.35 (0.28-0.46)	[0.33-0.35]	
26	292	0.34 (0.29-0.44)	[0.32-0.34]	
27	316	0.35 (0.28-0.44)	[0.33-0.37]	
28	333	0.33 (0.27-0.42)	[0.31-0.34]	
34-36 weeks	
1	18	—	—	
2	2273	0.80 (0.70-0.91)	[0.79-0.80]	
3	3115	0.75 (0.63-0.90)	[0.73-0.76]	
4	2954	0.62 (0.51-0.77)	[0.62-0.64]	
5	2677	0.56 (0.46-0.70)	[0.55-0.57]	
6	2329	0.51 (0.42-0.64)	[0.50-0.52]	
7	2012	0.50 (0.40-0.60)	[0.49-0.50]	
8	1670	0.47 (0.38-0.60)	[0.45-0.48]	
9	1377	0.46 (0.37-0.60)	[0.45-0.48]	
10	1247	0.43 (0.35-0.57)	[0.42-0.45]	
11	1178	0.42 (0.34-0.56)	[0.40-0.43]	
12	1053	0.42 (0.34-0.57)	[0.40-0.43]	
13	946	0.40 (0.32-0.53)	[0.40-0.42]	
14	938	0.40 (0.30-0.52)	[0.38-0.40]	
15	906	0.39 (0.30-0.50)	[0.37-0.39]	
16	765	0.39 (0.30-0.51)	[0.36-0.40]	
17	720	0.38 (0.30-0.50)	[0.36-0.39]	
18	774	0.36 (0.29-0.49)	[0.34-0.36]	
19	676	0.37 (0.29-0.48)	[0.35-0.38]	
20	661	0.34 (0.28-0.45)	[0.32-0.35]	
21	627	0.33 (0.26-0.44)	[0.31-0.33]	
22	619	0.33 (0.26-0.45)	[0.31-0.34]	
23	534	0.33 (0.26-0.43)	[0.31-0.34]	
24	523	0.31 (0.25-0.42)	[0.30-0.31]	
25	546	0.30 (0.23-0.40)	[0.30-0.32]	
26	516	0.31 (0.25-0.40)	[0.30-0.31]	
27	481	0.30 (0.23-0.40)	[0.29-0.29]	
28	476	0.30 (0.22-0.40)	[0.29-0.30]	
>=37 weeks	
1	59	0.80 (0.67-0.90)	[0.69-0.82]	
2	5453	0.76 (0.65-0.90)	[0.76-0.77]	
3	7962	0.69 (0.56-0.83)	[0.68-0.70]	
4	7604	0.56 (0.46-0.70)	[0.56-0.57]	
5	6672	0.50 (0.40-0.61)	[NA-NA]	
6	5677	0.46 (0.38-0.58)	[0.45-0.47]	
7	4690	0.43 (0.35-0.53)	[0.42-0.43]	
8	3912	0.41 (0.33-0.51)	[0.40-0.41]	
9	3236	0.40 (0.32-0.50)	[0.40-0.40]	
10	2853	0.40 (0.30-0.50)	[NA-NA]	
11	2591	0.40 (0.30-0.50)	[0.39-0.40]	
12	2315	0.39 (0.30-0.50)	[0.38-0.40]	
13	2130	0.37 (0.30-0.50)	[0.37-0.39]	
14	2021	0.36 (0.29-0.47)	[0.35-0.37]	
15	1832	0.35 (0.28-0.45)	[0.34-0.36]	
16	1576	0.35 (0.28-0.47)	[0.34-0.36]	
17	1515	0.34 (0.27-0.45)	[0.33-0.35]	
18	1447	0.33 (0.27-0.44)	[0.32-0.34]	
19	1330	0.32 (0.26-0.43)	[0.32-0.34]	
20	1259	0.31 (0.25-0.42)	[0.30-0.32]	
21	1178	0.31 (0.25-0.42)	[0.30-0.32]	
22	1100	0.30 (0.24-0.40)	[0.30-0.30]	
23	962	0.30 (0.24-0.42)	[0.30-0.32]	
24	921	0.30 (0.24-0.40)	[0.30-0.30]	
25	908	0.30 (0.23-0.40)	[0.29-0.29]	
26	882	0.30 (0.23-0.40)	[0.29-0.29]	
27	821	0.30 (0.23-0.39)	[0.28-0.30]	
28	824	0.30 (0.22-0.40)	[0.28-0.30]	
Values are median (interquartile range). — indicates fewer than 20 infants contributed data for that cell; value suppressed as unreliable. 95% BCa CI = bias-corrected accelerated bootstrapped confidence interval for the median (1000 replications; percentile bootstrap used as fallback where BCa failed due to tied values).