Indian J Pediatr 1991; 58 : 657-660 i i

Serum IgG at Birth in Preterm Appropriate-and Small- for-Gestational Age Newborns

Mahesh Sharma,* D. Laroia, R.K. Taluja and P.S. Mathur

Department of Pediatrics, B.J. Medical College and Ovil Hospital, Ahmedabad and *Department of Pediatrics, Kamla Raja Mother & Child Hospital,

G.R. Medical College, Gwalior

Serum IgG at birth was estimated in 31 preterm and 33 full term newborns, grouped according to their weight-for-gestational age. Preterm small-for-ges- tational age neonates were found to have significantly reduced IgG levels as compared to preterm appropriate-for-gestational age and full term small-for- gestational age newborns. It is suggested that preterms with intra-uterine growth retardation are most suitable for exogenous IgG supplementation to reduce neGnatal and postneonatal susceptibility to infections.

Key Words : IgG ; Preterms.

Infection remains a major problem in new- borns because early diagnosis is difficult and morbidity and mortality remain high. ~ Humoral deficiency in prematures is a cru- cial contributory factor to the increased sus- ceptibility to infection. 2 Though IgG is just one arm of the immune system, neverthe- less, it accounts for about 80% of serum immunoglobulin and is the chief component of the baby's serological defence, containing most of the antibacterial, antiviral, antipro- tozoal and antitoxic activity of the serum?

Levels of IgG at birth have been well documented in full term and premature newborns 4'5'6 but there are few studies

Reprint requests : Dr. M. Sharma, Assistant Professor, Department of Pediatrics (D-4), Civil Hospital & B.J. Medical College, Ahmedabad- 380 016.

measuring IgG in preterms with intra-uter- ine growth retardation (IUGR).

Results of trials of exogenous lgG ad- ministration in prematures also remain con- troversial so far. 7"10 This study analyses IgG status at birth in different groups of new- borns and attempts to select neonates who would be ideal for gammaglobulin supple- mentation.

MATERIAL AND METHODS

Blood samples were collected within 6 hours of birth from 33 full term and 31 pre- term newborns. Gestational age was deter- mined by maternal dates and Dubowitz as- sessment, u All newborns were classified into term or' preterm appropriate-for-gesta- tional age (TAGA or PAGA and term or preterm small-for-gestational age (TSGA or PSGA) groups (below-2SD) using re-

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658 THE INDIAN JOURNAL OF PEDIATRICS Voi. 58, No. 5

gional intra-uterine growth curves 12. Serum IgG was determined by Mancini's end-point method for radial immunodiffusion 13 using Tripartigen plates (confidence range _+ 15%). Congenitally mal formed and hy- poplastic babies were excluded from the study. Subsequent analysis was by Student's ' t ' test.

RESULTS

Serum IgG at birth was found to increase significantly with gestational age, from 28- 30 weeks onwards to 37-39 weeks (Table 1), and with birth weight (Table 2). In both full

term and preterm groups, small-for-gesta- tional age newborns had significantly lower IgG levels when compared to those appro- priate-for-gestational age (Table 3). Lowest serum IgG was recorded in PSGA new- borns.

DISCUSSION

The levels of lgG in preterms in our study are comparable to other Indian workers? ,6 Most of the maternofetal transfer of IgG occurs in the last trimester of pregnancy by an active" transport mechanism through Fc receptors (IgG~ > IgG2) in the human pla-

T~Lg 1. Serum IgG (iu/ml) and Gestational Age.

Group Gestational No.of IgG Comparison P' age (wk) cases (Mean _+ SD) of groups

1. 27 5 50.56 _+ 15.12 1 vs2 >0.05

2. 28-30 7 52.11 -+ 13.08 2 vs 3 < 0.01

3. 31-33 12 76.17 -+ 14.05 3 vs 4 <0.01

4. 34-36 7 98.93 -+ 15.79 4 vs 5 <0.01

5. 37-39 31 153.54 -+ 23.68 6 vs 5 >0.05

6. 40-42 2 132.25 -+ 29.62

Mean gestational age of group 1 to 4 -- 31.1 weeks ; Group 5, 6 = 38.2 weeks. * Student's "t" test

T,~t~ 2. Serum IgG (iu/ml) and Birth Weight

Group Birth No.of IgG Comparison P" weight (g) cases (Mean _+ SD) of groups

1. 1000 11 49.37 _+ 12.05 1 vs 2 <0.01

2. 1001-1500 13 74.57 _+ 11.85 2 vs 3 <0.01

3. 1501-2000 17 101.1 • 9.98 3 vs 4 <0.01

4. 2001-2500 8 14032 _+ 17.04 4 vs 5 <0.01

5. 2501-3000 5 168.22 _+ 8.09 6 vs 5 <0.01

6. 3001-3500 10 203.79 _+ 15.23 T

* Student "t" test

sHARMA ETAL : IgG IN NEWBORNS 659

T~L~ 3. Serum IgG (iu/ml) in Appropriate - and Small-for-Gestational Age Newborns.

Group No.of Mean gestational IgG Comparison P' cases age (wk) (Mean • SD) of groups

PAGA 17 30.7 86.24 • 17.91 PAGAvsPSGA <0.01

PSGA 14 31.6 54.14 • 14.97 TSGAvs PSGA <0.01

TAGA 15 38.0 191.93 • 21.66 TAGA vs PAGA < 0.01

TSGA 18 38.4 119.17 -+ 23.15 TAGAvsTSGA <0.01

*Student "t" test

PAGA = Preterm appropriate for gestational age; PSGA = Preterm small for gestational age; TAGA = Term AGA ; TSGA = Term SGA

cental tissue l' and/or by receptor mediated endocytosis, t5 Therefore, increase in gesta- tional age continues to increase IgG in the neonate as observed in this and other stud- ies 5,6 and maximum levels are reached by 37-39 weeks (present study) or by 38-42 weeks:

A positive correlation of lgG with birth weight, irrespective of gestational age, has also been noted earlier) 6 We have also found IUGR in full term neonates to re- duce IgG levels at birth to a significant ex- tent (TAGA vs TSGA, p < 0.01). Placental insufficiency/dysfunction probably leads to both IUGR and reduced IgG levels at birth:' ~5 In our study, this effect has been observed in preterms as well (PAGA vs PSGA, p < 0.01). PSGA neonates appear to be doubly compromised as regards lgG at birth, and we think that IUGR enhances the reduction of maternofetal transfer due to curtailed gestational age. Therefore, pre- cariously low levels of IgG (54.14 _+ 14.97 iu/ml) are met with in these newborns.

The physiologic trough of hypogam- maglobulinemia that occurs due to postna- tal decay of maternal IgG and inadequate IgG synthesis by the infant soon after birth has been found to be more pronounced in

Indian infants than their Western counter- parts) 7 PSGA neonates born with ex- tremely compromised IgG levels at birth can be expected to suffer from aft accentua- tion of this postnatal hypogammaglobuline- mia, TM perhaps far more than TSGA and even PAGA newborns. This can further in- crease their susceptibility to infections.

Exogenous IgG supplementation is a possible therapeutic answer to this prob- lem. Earlier trials 7~ have yielded less than satisfactory results. In a recent trial, 9 intra- venous gammaglobulin therapy did not de- crease the susceptibility to infection in pre- terms below 32 weeks of gestational age. In another trial ~~ it was found that in infants with birth weight _< 1500 g, the high suscep- tibility to generalized infection is mainly re- lated to immunologic factors (antibody and opsonin deficiency), which can be improved by ivlgG administration.

This study suggests that controlled trials of ivlgG supplementation in tropical PSGA neonates could be far more rewarding, par- ticularly because the already higher suscep- tibility to infection in these babies may filr- ther increase with advancing postnatal age. If exogenous lgG can diminish the suscepti- bility to infection in this group, neonates

660 THE INDIAN JOURNAL OF PEDIATRICS Vol. 58, No. 5

born with comparatively higher IgG levels (TSGA and PAGA) surely stand a better chance to benefit from such therapy.

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