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Serum protein-bound iodine of mothers and infants at delivery in premature and term pregnancies
Serum protein-bound iodine of mothers and infants at delivery in premature
and term pregnancies HARVEY ROSE, M.D. KEITH P. RUSSELL, M.D. PAUL STARR, M.D. Los Angeles, California
blood was performed in the following manner: Paired clamps were placed proximally and distally on the umbilical cord at cessation of umbilical arterial pulsations. By cutting in between each pair of clamps, the cord was obtained intact with its contents of arterial and venous blood. By clamping the umbilical arteries alone on one end, and holding that end dependent, the vein was allowed to drain into a test tube; it was then gently stripped permitting maximal evacuation. The vein was likewise clamped on end and the arterial contents were similarly collected. Umbilical arterial samples contained only 1 to 4 c.c. of blood, while the vein gave more than 5 c.c. for each sample. The ordinary so-called "cord blood" samples were obtained by allowing the cut end of the umbilical cord to drain into a test tube before delivery of the placenta. The cord blood as usually collected is primarily umbilical venous blood since the arteries are constricted after they cease pulsating and give up little of their contents. Maternal blood was obtained by antecubital venepuncture within 1 hour after the delivery. The criteria of premature deliveries indude: ( 1) gestation of less than 36 weeks; (2) birth weight of less than 2,500 grams; and (3) if the preceding were equivocal, a crown-heel length of less than 47 em. ( 18.6 inches) or head circumference of less than
T H I s report presents some determinations of the levels of the protein-bound iodine ( PBI) in maternal vein and umbilical cord blood of normal mothers and their term and premature infants taken at time of delivery. Materials and methods
The patients in this study were delivered on the Obstetrical Service of the Los Angeles County Hospital. The majority of them were Negro or Mexican. The PBI was determined in the venous blood of 38 mothers at term and 27 mothers who were delivered of premature infants. It was also determined in the umbilical cord blood of 84 premature infants and 67 term infants. In 18 of the term deliveries, paired maternal and cord bloods were obtained from the mother and the infant at or shortly following delivery. In these 18 patients the blood from the umbilical artery was obtained separately from that of the umbilical vein. Separation of umbilical arterial and venous
From the Obstetrical Service, Los Angeles County Hospital, and the Department of Obstetrics and Gynecology, University of Southern California School of Medicine. Supported by United States Public Health Service Grant No. A-2430 of the NIH Division of Arthritis and Metabolic Diseases.
767
768
.Jttly l!l, l!Hi I
Rose, Russell, and Starr
\nt. ,I ( ~h:-.L &
33 em. ( 13 inches). Twins were excluded from the infant group of the study, but not from the maternal group for their weights may occasionally classify them falsely as premature. Four uncontaminated samples of amniotic fluid were obtained at the time of the artificial rupture of the membranes and were measured for PBI. This was performed by
U~n~··.
direct needle aspiration thn>u~h the partially dilated cervix. The PBI determinations were carried out according to the Ware modification of the Barker dry ash method. 1 Not all determinations were made in duplicate; however, adequate samples and spot checks were performed in duplicate and at no time did cliff erences exceed 0. 7 meg. per 100 c.c. The
Table I. Serum PBI of term maternal vein, umbilical vein, and artery specimens obtained simultaneously ------,----------------
Code No.
Umbilical arterv
8.6 13.0 7.1 9.8 7.5 7.8 6.5 7.4 8.4 8.0 8.3 10.0 9.9 8.4 9.2 9.0 6.2 7.7
9.0 R1 5.5 6.8 4.4 3.9 5.6 9.3 6.8 6.1 8.4 9.3 7.5 7.5 7.1 6.0 7.1 7.6
7.1 5.0 .1.2 5.5 +.0 4.4 4.8 8.7
1.9 :> 0 0.3 1.3 0.4 --0.5 0.8 0.6 -0.5
6.0 8.5 8.7 7.8 7.7 7.:l 6.7 7.2 7.8
0.1
8.5 ± 1.56
7.0 ± 1.56
6. 7 ± 1.51
45 46 ,17
values:
Umbilical vein versus artery
Umbilical vein
H
p
---·-·-~----~-·-~---·-
Maternal vein
9 10 15 16 17 21 26 33 35 37 39 41 42 43
Mean and standard deviation
-
2 versus 3
n
Maternal
-0.1 0.6
artery
-0 ..4
1.5
4.9
7.9
1.6 3.0 3.1 3.9 0.9 -1.9 1.6 1.9 -0.1 0.7
-o.:~
2.4
-0.~
0.9 2.1 :UJ -0.9 0.1
-0.2 -0.7 -0.1 -0.2
Maternal l'ein versu.r umbilical
0.3:~
1.9 4.3 3.5 3.4 1.7 -1.3 1.1
2.0 -0.2 1.3 2.1 0.7 1.9 2.3 -1.0 -0.1
1.51
2.0
= 0.02; 2 versus 4 = 0.01; 3 versus 4 = 0.60.
Table II ·--~-·----
Mean PBI (meg.%)
- ·-----------··--I I I
Full term Premature
Difference p of means value
Maternal (38)
No.
Infant (67)
8.2 + 1.5 (range 5.0 to 13.0)
38
6.7 ± 1.2 (range 4.1 to 9.3)
67
1.5
0.01
7.5 + 2.0 (range 3.8 to 11.8)
27
5.8 + 1.3 (range 3.9 to 9.0)
64*
1.7
0.01
Difference Term versus premature mothers of means 0.7 p value
I No.
----
0.4
*Surviving premature infants only.
Term venus surviving premature infants with cord blood 0.9 0.005
Protein-bound iodine of mothers and infants
Volum" 86 Number 6
769
Tablt: III. Surviving and dying premature infants cord PBI's according to weights* Liue
907.2 to 1,445.8 1,814.4 to 2,466.5
Average PBI
5.7 6.0
----~---------
--
No. in
Dead Weight (£!rams)
Average PBit met(. % (range)
No. in
f!,fOU/J
255 878
5.3 (4.2 to 8.5)
6
907.2
5.1 (3.9 to 6.5)
9
1,64+3 1,814 2,211
5.2 ( 4.1 to 7.2)
4
1
17 47
5.8 (3.9 to 9.0)
---------------~-----~-------------------
group
5.2 (4.7)+
*p value PBPs of ~urviving infants versus PBI's of dying infants == 0.05. tlndividual values in Table IV. !Omitting 2 high values.
differences in duplicate samples tested were usually less than 0.5 meg. per cent. Results
1. The PBI values for the 4 clean arumotic fluid specimens were 0.3, 0.6, 0.6, and 0.8 meg. per cent. 2. In the special group of 18 patients (Table I) the maternal PBI was greater than that of either umbilical vessel in all but 4. The maternal vein-umbilical vein difference of the means was 1.5 meg. per cent with a range of from -1.9 to +4.9; the p value of this difference is 0.02. The maternal vein-umbilical artery difference of the means was 1.8 meg. per cent with a range from -1.3 to +7.9, the p value being 0.01. The difference between the means of the PBI's of the umbilical vein and umbilical artery blood was 0.3 meg-. per cent with a range from -0.7 meg. per cent to +3.0 meg. per cent, there being no significant difference, with the p value of 0.60. 3. The r1-1ean venous PBI of the 27 patients with premature deliveries was 7.5 ± 2.0 meg. per cent (range 3.8 to 11.8) while the 38 full-term maternal group had a mean venous PBI of 8.2 ± 1.5 meg. per cent (range 5.0 to 13.0) (Table II). The difference between the means of 0. 7 meg. per cent was not statistically significant for these somewhat smaller groups, the p value being 0.4. The difference between the means of
full-term maternal and infant group was 1.5 meg. per cent, while that of the premature group was 1.7 meg. per cent (Table II); both of the differences were statistically significant. 4. The mean cord blood PBI for the 64 surviving premature infants was 5.8 meg. per cent ± 1.3 (range 3.9 to 9.0) and for the 67 full-term babies was 6. 7 ± 1.2 meg. per cent (range 4.1 to 9.3) (Table II). The difference between the means of 0.9 meg. per cent was statistically significant with a p value of 0.005. 5. There were 19 deaths attributable to prematurity in the group of 64 premature infants. These deaths do not include stillbirths. The life-span was from several hours to several days. The average weight of these 19 was 1,247 grams with an average gestation length of 28 weeks, leaving no doubt as to the extreme prematurity of the group. This group's mean PBI was 5.2 meg. per cent, whereas the mean PBI for the 64 living prernature infants was 5.8 meg. per cent (Table III). The difference between the means of 0.6 meg. per cent gives a p value of 0.05. It appears, therefore, that the surviving premature babies had a statistically significant higher average PBI. If two unusually high PBI values in the premature infants who died are omitted, the difference is even more striking. It should be noted that there were no survivors in the 6 pre-
770 Rose, Russell, and Storr
July 15, 1963 c\lll.
Table IV. Premature deaths according to weight Birth weight (grams)
Length of gestation (weeks)
PBi
(mcf!. %)
0 to 1-15
Case No. 652.0 538.6 623.7 680.4 255.2 878.8
1 2 3 4 5 6
Average
595.3
22 24 24 29 20 24 24
(omitting 8.2 2-0 to 3-15
.,I
8 9
"'
lU
11
12 13 14 15
Average 4-0 to 5-7 16 17 18 19
1
1\..,t"..,
1,644.3 1,048.9
34 35 24
f'l
'lC
1,219.0 992.2 1,615.9 1,332.4 907.2
1,247.4
28 26 30 30 26 29
1,814.4 2,211.4 1,871.1 1,927.8
30 35 30 36
l,L./3./
1
1.-:JA
I,l.J'"t.U
---
1,956.1
4U
33
(omitting 7.2 Total average
1,24 7.4
28
4.2 4.2 5.6 4.0 5.8 8.2 5.3 4.7)
= C
A
u.u
4.5 4.0 c" U.4 4.6 5.6 6.5 4.3 3.9 5.1
i.2 4.1 4.2 5.1 5.2 4.4)
=
5.2
(omitting 7.2 and 8.2 = 4.7)
mature infants whose birth weight was less than 900 grams, but their mean PBI was no difrerent from those higher birth weight babies who also died. Comment
The mean PBI values obtained in this study during pregnancy and at term in both mothers and infants are very similar to those reported by others. 2 • 3 Friis found an average difference of. 1.59 meg. per cent betv:een full . . term maternal and cord blood PBI's, the values being 8.18 and 6.59, re;pectively. The latter figure closely agrees
J
Oh,t. & Gym•e.
with our mean PBI of 6. 7 meg. per cent in the full-term infant. The data presented here appear to demonstrate a PBI value of the baby that, on the average, is about 20 per cent less than that of the mother. No equilibration across the placenta can be demonstrated. The mechanism of the relation of maternal and infant PBI's has been discussed by others. 4 - 6 Man and co-workers'' have reported a mean term cord butanolextractable iodine (BEl) of 6.7 (range 4.4 to 9.5) and mean term maternal BEl of 7.0 (range 5.3 to 9.2). Since the BEl tends to range about 0.5 meg. lower than the PBI, these figures are comparable to ours. Danowski/ however, found the mean PBI of 20 infants, age 0 to 11.9 hours, to be 8.3 ± 2.4. It is not stated how n-tany of these had cord blood. The mean maternal PBI of 7.8 ± 1.3 was given, but it was not indicated when the bloods were drawn. Since Danowski noted a rise in PBI in the first few days of life, his higher mean for PBI may be caused by the bloods being drawn several hours after mrtn. vVe have previously pointed out the value of matched pairing of maternal and cord bloods in studies of this type.' It is interesting to note that the mothers whose pregnancies terminated prematurely had serum PBI levels which were not significantly different from those of the mothers whose pregnancies continued to term. But their offspring had definitely altered PBI's, the prematures being significantly less than the term babies. Does this indicate less normal hormone metabolism by the placenta, the liver, the pituitary, or the thyroid of the premature infants, or does it merely indicate that the infants who arc younger normally have lower circulating thyroxine? The premature infants who survived had higher PBI's than those of approximately the same weight who died, but several individuals among the babies who died had PBrs that were in the range of the term baby PBI's (Table IV). Finally, it should be noted that both maternal and infant levels in this series of indigent individuals are significantly lower
Volume 86 Number 6
than those found in a previously reported study of ours which included private patient~. of a generally higher socioeconomic level. 7 In both series the same methods and facilities were utilized in the technical determinations of the protein-bound iodine. Summary
The protein-bound iodine levels of premature infants appeared to be significantly less than those of term infants. The cord blood PBI on the average was noted to be about 20 per cent less than the maternal
RHERENCES
1. ·ware, Arnold G., Grillhoesl, Kay, and Grant, Mary: In Starr, P., editor: Hypothyroidism, Springfield, Ill., 1954, Charles C Thomas, Publisher, p. 22. A modification from Barker, S. B., Humphrey, M. V., and Soley, N. H.: j. Clin. Invest. 30: 55, 1951. 2. Friis, T., and Sacher, E.: Acta endocrinol. 18: 428, 1955. 3. Russell, K. P.: Obst. & Gynec. Surv. 9: 15 7, 1954.
Protein-bound iodine of mothers and infants 771
PBI in both premature and term deliveries. The mean full-term cord PBI in our series of 67 term infants (6. 7 meg. per cent) agreed within 0.1 meg. per cent with other small published groups of 9 and 19 cases each. There was no significant difference in the mean PEl's of the maternal term group and the premature group. However, the number of cases was less than those in the infant study. The amniotic fluid contains no appreciable amount of protein-bound iodine.
A
T'io---- __ 1_!
..,., C'l Pediatrics 7: 240, .;:,., et al.: 1951. 5. Heinemann, M., Johnson, C. E., and Man, E. B.: J. Clin. Invest. 27: 91, 1948. 6. Man, E. B., Pickering, D. E., Walker, J., and Cooke, R. E.: Pediatrics 9: 32, 1952. 7. Russell, K. P., Tanaka, S., and Starr, P.: A~L J. 0BST. & GYNEC. 79: 718, 1960.
"1'.
.LJaUUW:SKl,
~.
511 S. Bonnie Brae St. Los Angeles 57, California (Dr. Russell)
and term pregnancies HARVEY ROSE, M.D. KEITH P. RUSSELL, M.D. PAUL STARR, M.D. Los Angeles, California
blood was performed in the following manner: Paired clamps were placed proximally and distally on the umbilical cord at cessation of umbilical arterial pulsations. By cutting in between each pair of clamps, the cord was obtained intact with its contents of arterial and venous blood. By clamping the umbilical arteries alone on one end, and holding that end dependent, the vein was allowed to drain into a test tube; it was then gently stripped permitting maximal evacuation. The vein was likewise clamped on end and the arterial contents were similarly collected. Umbilical arterial samples contained only 1 to 4 c.c. of blood, while the vein gave more than 5 c.c. for each sample. The ordinary so-called "cord blood" samples were obtained by allowing the cut end of the umbilical cord to drain into a test tube before delivery of the placenta. The cord blood as usually collected is primarily umbilical venous blood since the arteries are constricted after they cease pulsating and give up little of their contents. Maternal blood was obtained by antecubital venepuncture within 1 hour after the delivery. The criteria of premature deliveries indude: ( 1) gestation of less than 36 weeks; (2) birth weight of less than 2,500 grams; and (3) if the preceding were equivocal, a crown-heel length of less than 47 em. ( 18.6 inches) or head circumference of less than
T H I s report presents some determinations of the levels of the protein-bound iodine ( PBI) in maternal vein and umbilical cord blood of normal mothers and their term and premature infants taken at time of delivery. Materials and methods
The patients in this study were delivered on the Obstetrical Service of the Los Angeles County Hospital. The majority of them were Negro or Mexican. The PBI was determined in the venous blood of 38 mothers at term and 27 mothers who were delivered of premature infants. It was also determined in the umbilical cord blood of 84 premature infants and 67 term infants. In 18 of the term deliveries, paired maternal and cord bloods were obtained from the mother and the infant at or shortly following delivery. In these 18 patients the blood from the umbilical artery was obtained separately from that of the umbilical vein. Separation of umbilical arterial and venous
From the Obstetrical Service, Los Angeles County Hospital, and the Department of Obstetrics and Gynecology, University of Southern California School of Medicine. Supported by United States Public Health Service Grant No. A-2430 of the NIH Division of Arthritis and Metabolic Diseases.
767
768
.Jttly l!l, l!Hi I
Rose, Russell, and Starr
\nt. ,I ( ~h:-.L &
33 em. ( 13 inches). Twins were excluded from the infant group of the study, but not from the maternal group for their weights may occasionally classify them falsely as premature. Four uncontaminated samples of amniotic fluid were obtained at the time of the artificial rupture of the membranes and were measured for PBI. This was performed by
U~n~··.
direct needle aspiration thn>u~h the partially dilated cervix. The PBI determinations were carried out according to the Ware modification of the Barker dry ash method. 1 Not all determinations were made in duplicate; however, adequate samples and spot checks were performed in duplicate and at no time did cliff erences exceed 0. 7 meg. per 100 c.c. The
Table I. Serum PBI of term maternal vein, umbilical vein, and artery specimens obtained simultaneously ------,----------------
Code No.
Umbilical arterv
8.6 13.0 7.1 9.8 7.5 7.8 6.5 7.4 8.4 8.0 8.3 10.0 9.9 8.4 9.2 9.0 6.2 7.7
9.0 R1 5.5 6.8 4.4 3.9 5.6 9.3 6.8 6.1 8.4 9.3 7.5 7.5 7.1 6.0 7.1 7.6
7.1 5.0 .1.2 5.5 +.0 4.4 4.8 8.7
1.9 :> 0 0.3 1.3 0.4 --0.5 0.8 0.6 -0.5
6.0 8.5 8.7 7.8 7.7 7.:l 6.7 7.2 7.8
0.1
8.5 ± 1.56
7.0 ± 1.56
6. 7 ± 1.51
45 46 ,17
values:
Umbilical vein versus artery
Umbilical vein
H
p
---·-·-~----~-·-~---·-
Maternal vein
9 10 15 16 17 21 26 33 35 37 39 41 42 43
Mean and standard deviation
-
2 versus 3
n
Maternal
-0.1 0.6
artery
-0 ..4
1.5
4.9
7.9
1.6 3.0 3.1 3.9 0.9 -1.9 1.6 1.9 -0.1 0.7
-o.:~
2.4
-0.~
0.9 2.1 :UJ -0.9 0.1
-0.2 -0.7 -0.1 -0.2
Maternal l'ein versu.r umbilical
0.3:~
1.9 4.3 3.5 3.4 1.7 -1.3 1.1
2.0 -0.2 1.3 2.1 0.7 1.9 2.3 -1.0 -0.1
1.51
2.0
= 0.02; 2 versus 4 = 0.01; 3 versus 4 = 0.60.
Table II ·--~-·----
Mean PBI (meg.%)
- ·-----------··--I I I
Full term Premature
Difference p of means value
Maternal (38)
No.
Infant (67)
8.2 + 1.5 (range 5.0 to 13.0)
38
6.7 ± 1.2 (range 4.1 to 9.3)
67
1.5
0.01
7.5 + 2.0 (range 3.8 to 11.8)
27
5.8 + 1.3 (range 3.9 to 9.0)
64*
1.7
0.01
Difference Term versus premature mothers of means 0.7 p value
I No.
----
0.4
*Surviving premature infants only.
Term venus surviving premature infants with cord blood 0.9 0.005
Protein-bound iodine of mothers and infants
Volum" 86 Number 6
769
Tablt: III. Surviving and dying premature infants cord PBI's according to weights* Liue
907.2 to 1,445.8 1,814.4 to 2,466.5
Average PBI
5.7 6.0
----~---------
--
No. in
Dead Weight (£!rams)
Average PBit met(. % (range)
No. in
f!,fOU/J
255 878
5.3 (4.2 to 8.5)
6
907.2
5.1 (3.9 to 6.5)
9
1,64+3 1,814 2,211
5.2 ( 4.1 to 7.2)
4
1
17 47
5.8 (3.9 to 9.0)
---------------~-----~-------------------
group
5.2 (4.7)+
*p value PBPs of ~urviving infants versus PBI's of dying infants == 0.05. tlndividual values in Table IV. !Omitting 2 high values.
differences in duplicate samples tested were usually less than 0.5 meg. per cent. Results
1. The PBI values for the 4 clean arumotic fluid specimens were 0.3, 0.6, 0.6, and 0.8 meg. per cent. 2. In the special group of 18 patients (Table I) the maternal PBI was greater than that of either umbilical vessel in all but 4. The maternal vein-umbilical vein difference of the means was 1.5 meg. per cent with a range of from -1.9 to +4.9; the p value of this difference is 0.02. The maternal vein-umbilical artery difference of the means was 1.8 meg. per cent with a range from -1.3 to +7.9, the p value being 0.01. The difference between the means of the PBI's of the umbilical vein and umbilical artery blood was 0.3 meg-. per cent with a range from -0.7 meg. per cent to +3.0 meg. per cent, there being no significant difference, with the p value of 0.60. 3. The r1-1ean venous PBI of the 27 patients with premature deliveries was 7.5 ± 2.0 meg. per cent (range 3.8 to 11.8) while the 38 full-term maternal group had a mean venous PBI of 8.2 ± 1.5 meg. per cent (range 5.0 to 13.0) (Table II). The difference between the means of 0. 7 meg. per cent was not statistically significant for these somewhat smaller groups, the p value being 0.4. The difference between the means of
full-term maternal and infant group was 1.5 meg. per cent, while that of the premature group was 1.7 meg. per cent (Table II); both of the differences were statistically significant. 4. The mean cord blood PBI for the 64 surviving premature infants was 5.8 meg. per cent ± 1.3 (range 3.9 to 9.0) and for the 67 full-term babies was 6. 7 ± 1.2 meg. per cent (range 4.1 to 9.3) (Table II). The difference between the means of 0.9 meg. per cent was statistically significant with a p value of 0.005. 5. There were 19 deaths attributable to prematurity in the group of 64 premature infants. These deaths do not include stillbirths. The life-span was from several hours to several days. The average weight of these 19 was 1,247 grams with an average gestation length of 28 weeks, leaving no doubt as to the extreme prematurity of the group. This group's mean PBI was 5.2 meg. per cent, whereas the mean PBI for the 64 living prernature infants was 5.8 meg. per cent (Table III). The difference between the means of 0.6 meg. per cent gives a p value of 0.05. It appears, therefore, that the surviving premature babies had a statistically significant higher average PBI. If two unusually high PBI values in the premature infants who died are omitted, the difference is even more striking. It should be noted that there were no survivors in the 6 pre-
770 Rose, Russell, and Storr
July 15, 1963 c\lll.
Table IV. Premature deaths according to weight Birth weight (grams)
Length of gestation (weeks)
PBi
(mcf!. %)
0 to 1-15
Case No. 652.0 538.6 623.7 680.4 255.2 878.8
1 2 3 4 5 6
Average
595.3
22 24 24 29 20 24 24
(omitting 8.2 2-0 to 3-15
.,I
8 9
"'
lU
11
12 13 14 15
Average 4-0 to 5-7 16 17 18 19
1
1\..,t"..,
1,644.3 1,048.9
34 35 24
f'l
'lC
1,219.0 992.2 1,615.9 1,332.4 907.2
1,247.4
28 26 30 30 26 29
1,814.4 2,211.4 1,871.1 1,927.8
30 35 30 36
l,L./3./
1
1.-:JA
I,l.J'"t.U
---
1,956.1
4U
33
(omitting 7.2 Total average
1,24 7.4
28
4.2 4.2 5.6 4.0 5.8 8.2 5.3 4.7)
= C
A
u.u
4.5 4.0 c" U.4 4.6 5.6 6.5 4.3 3.9 5.1
i.2 4.1 4.2 5.1 5.2 4.4)
=
5.2
(omitting 7.2 and 8.2 = 4.7)
mature infants whose birth weight was less than 900 grams, but their mean PBI was no difrerent from those higher birth weight babies who also died. Comment
The mean PBI values obtained in this study during pregnancy and at term in both mothers and infants are very similar to those reported by others. 2 • 3 Friis found an average difference of. 1.59 meg. per cent betv:een full . . term maternal and cord blood PBI's, the values being 8.18 and 6.59, re;pectively. The latter figure closely agrees
J
Oh,t. & Gym•e.
with our mean PBI of 6. 7 meg. per cent in the full-term infant. The data presented here appear to demonstrate a PBI value of the baby that, on the average, is about 20 per cent less than that of the mother. No equilibration across the placenta can be demonstrated. The mechanism of the relation of maternal and infant PBI's has been discussed by others. 4 - 6 Man and co-workers'' have reported a mean term cord butanolextractable iodine (BEl) of 6.7 (range 4.4 to 9.5) and mean term maternal BEl of 7.0 (range 5.3 to 9.2). Since the BEl tends to range about 0.5 meg. lower than the PBI, these figures are comparable to ours. Danowski/ however, found the mean PBI of 20 infants, age 0 to 11.9 hours, to be 8.3 ± 2.4. It is not stated how n-tany of these had cord blood. The mean maternal PBI of 7.8 ± 1.3 was given, but it was not indicated when the bloods were drawn. Since Danowski noted a rise in PBI in the first few days of life, his higher mean for PBI may be caused by the bloods being drawn several hours after mrtn. vVe have previously pointed out the value of matched pairing of maternal and cord bloods in studies of this type.' It is interesting to note that the mothers whose pregnancies terminated prematurely had serum PBI levels which were not significantly different from those of the mothers whose pregnancies continued to term. But their offspring had definitely altered PBI's, the prematures being significantly less than the term babies. Does this indicate less normal hormone metabolism by the placenta, the liver, the pituitary, or the thyroid of the premature infants, or does it merely indicate that the infants who arc younger normally have lower circulating thyroxine? The premature infants who survived had higher PBI's than those of approximately the same weight who died, but several individuals among the babies who died had PBrs that were in the range of the term baby PBI's (Table IV). Finally, it should be noted that both maternal and infant levels in this series of indigent individuals are significantly lower
Volume 86 Number 6
than those found in a previously reported study of ours which included private patient~. of a generally higher socioeconomic level. 7 In both series the same methods and facilities were utilized in the technical determinations of the protein-bound iodine. Summary
The protein-bound iodine levels of premature infants appeared to be significantly less than those of term infants. The cord blood PBI on the average was noted to be about 20 per cent less than the maternal
RHERENCES
1. ·ware, Arnold G., Grillhoesl, Kay, and Grant, Mary: In Starr, P., editor: Hypothyroidism, Springfield, Ill., 1954, Charles C Thomas, Publisher, p. 22. A modification from Barker, S. B., Humphrey, M. V., and Soley, N. H.: j. Clin. Invest. 30: 55, 1951. 2. Friis, T., and Sacher, E.: Acta endocrinol. 18: 428, 1955. 3. Russell, K. P.: Obst. & Gynec. Surv. 9: 15 7, 1954.
Protein-bound iodine of mothers and infants 771
PBI in both premature and term deliveries. The mean full-term cord PBI in our series of 67 term infants (6. 7 meg. per cent) agreed within 0.1 meg. per cent with other small published groups of 9 and 19 cases each. There was no significant difference in the mean PEl's of the maternal term group and the premature group. However, the number of cases was less than those in the infant study. The amniotic fluid contains no appreciable amount of protein-bound iodine.
A
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..,., C'l Pediatrics 7: 240, .;:,., et al.: 1951. 5. Heinemann, M., Johnson, C. E., and Man, E. B.: J. Clin. Invest. 27: 91, 1948. 6. Man, E. B., Pickering, D. E., Walker, J., and Cooke, R. E.: Pediatrics 9: 32, 1952. 7. Russell, K. P., Tanaka, S., and Starr, P.: A~L J. 0BST. & GYNEC. 79: 718, 1960.
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511 S. Bonnie Brae St. Los Angeles 57, California (Dr. Russell)