Role Of Maternal Serum Homocysteine Level on F etal Birth Weight

Objective: The present study has been conducted to investigate the role of plasma homocysteine on neonatal birth weight. Methods: This prospective cross sectional analytical study was conducted in the inpatient.departrnent of obstetrics & gynecology, Dhaka Medical College Hospital on 120 term, singleton pregnant women. Pregnant women with plasma total homocysteine >15 pmol/L were termed as having hyperhomocysteinemia (case, n: 25), while women with plasma total homocysteine <15 pmol/L were considered as norrral (control, n: 95). Neonatal birth weight was the main outcome variable which was compared between case and control groups. Result: The entire women in the case group were in their 3rd decades, while 80% of the control group were in this age range and 10% was below 20 and, l0% above 30 years old. The cases were older than the controls (25.6 + 2.0 vs. 23.7 + 4.7 years, p : 0.051). Over three-quarters (76Yo) of the cases were SSC level educated, while majority (84.2%) of the contols was primary level educated. Eighty percent of the neonates born of mothers with hyperhomocysteinemia were of low birth weight as opposed to only 9.5Yo in the conhol group. The mothers of case-group carryr nearly 40(95% of CI: ll.5 126.4) times higher risk of having low birth weight babies than the mothers with normal homocysteine level. The mean bffi weight of neonates of case group was observed to be significantly higher Q3 + 0.4 kg) than that of control group (2.2 t 0.4 kg). Correlation between the two variables shows that as plasma homocysteine level of women increases the birth weight of neonates decreases bearing an inverse relationship between these two variables (r: 0.326,p < 0.001). Conclusion: Pregnant women with elevated plasma total homocysteine carry much higher risk of giving low birth weight babies than the women with normal or low level of total homocysteine. Thus, measuring total homcysteine during pregnancy is of much clinical importance as corrective measure could be taken to avert the adverse pregnancy outcome.


Introduction :
The period of intrauterine growth and development is one of the most vulnerable periods in the human life cycle.The weight of the infant at birth is a powerful predictor of infant growth and survival, and is dependent on maternal health and nutrition during pregnancy.In developing countries, the majority of low birth-weight (LBW) infants because of intrauterine growth retardation (IUGR) are born small at term (> 37 weeks of gestation).Low birth weight leads to an impaired growth of the infant with its consequent risks of u higher .mortalifyrate, increased morbidity', impaired mental developmenf, and the risk of chronic adult disease.Infants who weigh 2,000-2,499 g at Address for Correspondence: Dr. Aftina Begum, Assistant Professor Gynae & Obs Dept.DMCH, Dhaka.1n6 [BSMMU J 201s ; 6 (2) : ] t6-120J birth have a four-fold higher risk of neonatal death than those who weigh 2,500-3,499 g.The more severe the growth restriction within the LBW category the higher is the risk of deathl.Maternal nutrition is, therefore, an important factor from public health point of view because it is susceptible to public health interventions.
Realizing this concept, recently interest has turned to specific micronutrients as possible limiting factors for foetal growth.It is now known that the prevalence of vitamin B 12 deficiency is high in the Indian populationa.
It may be important to look into the potential role of vitamin B L2 defrciency in elevating plasma homocysteine (Hcy) levels in pregnancy, and its implications for adverse pregnancy outcomes including low birth weights.Methionine synthase is an enz1r'me which catalyzes the methyla- tion of homocysteine to methionine using vitamin    Bl2 as a cofactor and methyltetrahydrofolate as a substrate6.Formation of methionine through this pathway represents arl important component of the one-carbon metabolism for synthesis of phospholipids, proteins, myelin, catecholamines, DNA and RNA.A deficiency of either vitamin B 12 andlor folic acid is likely to affect this pathway resulting in an elevation of plasma Hcy with a relatively low methionine 1eve17.have reported that moth- ers in the highest tHcy (total homocysteine) tertile at 8 weeks of pregnancy had three times (OR: 3.26; 95o/o CI: 1 .05, 10. 13) and at labor had nearly four times (OR: 3 .651,95% CI: 1.15, 11.56) the odds of giving birth to a neonate in the lowest birth weight tertile.Dietary deficiencies for Vit-B6, B 12, or folate are associated with elevated homo- cysteine concentrations.
Several factors increase plasma homocysteine level like genetic defects in homocysteine metabolism (CBS, MTHFR, Methionine synthase), nutritional deficiencies in vitamin cofactors (Folate, vitamrn Bl2, vitamin 86), diseases (pernicious anemia, renal impairment, hypothy- roidism, malignancy: acute lymphoblastic leukemia;, carcinoma of the breast, ovary and pancre&S, severe psoriasis), medications/toxins Folat e arrtagonists-metho- trexate, phenytoin, cafuamazepine, vitamin B6 antagonist-theophylline, azarabine, oestrogen containing oral contraceptives, ctgarette smoking, increasing d9a, male sex and menopausee.The small-for-date babies are usually ascribed to the small size and chronic undernutrition of mothers.Vitamin B 12 and folate play an important role in nucleic acid metabolism cell growth and proliferation and are important determinants of fetal growth8'lO.
From the above background information, it is evident that circulating total homocysteine may itself increase the risk of a wide range of abnormalities.Low birth-weight is one of them.The clinical implication of the present study lies in the facts that 1) low birth weight babies arc at increased risk of higher morbidity and mortality and 2) hyperhomocystenemia carl usually be corrected by supplementation with B vitamins including folic acid during pregnancy.So the findings derived from the study could be extrapolated to formulate a plan for supplementation of vitamin 812 and folate to pregnant women at risk of developing hyperhomocysteinemia.
Methods : The present prospective study was carried out in the inpatient department of obstetrics & gynecology, Dhaka Medical College Hospital over a period of 2 years between Jarruary 2009 to December 2010.The study population was comprised of pregnantwomen at their 3'd trimesters attending Dhaka Medical College Hospital, Dhaka for antenatal check-up.Singleton pregnant women at their third trimester (between 37 40 weeks) with plasma total homocysteine > 15 pmoLlL were considered as cases and with plasma total homocysteine < 15 pmol/L were taken as controls.However, pregnant women with diabetes mellifus, chronic renal disease, chronic hyper tension, preeclampsia, thyroid disease and other medical diseases or with smoking habits were excluded from the study.
A total of I20 term pregnant women admitted in the labour ward for delivery were consecutively included in the study.A11 the study subjects were tested for plasma homocysteine level during their stay in the hospital.Of them 25 had tHcy > 15 pmol/L (designated as Case) and the rest 95 had tHcy < 15 pmol/L (Control).Neonates weighing < 2500 g at birth were termed as low birth- weight (LBW).Quantitative measurement of serum total homocysteine was estimated by fluorescence polartzation immunoassay (FPIA) method by Abott AxSYM system analyzer".
Collected data were processed using software SPSS (Statistical package for social sciences) version 11.5.The test statistics used to analyse the data were descriptive statistics, Chi-square (f), Student t-Test and Odds Ratio with 95% confidence interval.Spearman coffelation was done to see the relationship between maternal plasma homocysteine and neonatal birth weight.Level of significance was set at 0.05 and p-value ( 0.05 was considered significant.

Result :
Age distributions of the study subjects demonstrate that all the women in the case group were in the range of 20 -30 years, while 80Yo of the control groups were in this age range and I0% was below 20 and l0% above 30 years of tt7 age.The cases were a bit older than the controls.(25.6 * 2.0 vs. 23.7 * 4.7 years, p_0.051).More than three- quarter (76%) of the cases were SSC level educated while majority (84.2%) of the controls was primary level educated.Cases were mainly rural residents (64%) and the rest 36% were urban residents.Forty percent of the controls were from semi-urbanarea,34.7oh from rural and 25.3% from urban area(Table I).
Eighty percent of the cases gave birth to low birth weight neonates as opposed to only 9.5% of the controls.The risk having low birth weight babies in case group is more than 38(95% of CI : 1 1 .5 -126.4) times higher than that in the control group.The mean birth weight of neonates of mothers with hyperhomcysteinemia (serum homocysteine > 15 nmol/L) was observed to be significantly higher (2.8 * 0.4 kg) than that of mothers having normal homocyst- eine level (2.2 * 0.4 kg) (Table II).Correlation between the two variables shows that as plasma homocysteine level of women increases the birth weight of neonates decreases giving an inverse relation between the variables of interest (r: -0.3 26,p< 0.001) (fig.T4).The present study aimed at finding the association between the level of maternal homocystine at term and neonatal birth weight include d atotal of 100 samples with single tone uncomplicated pregnancy.The study showed that pregnant women with hyperhomocysteinemia (<15 pmol/L) had neonates with mean birth weight 2.8 kg, while mothers with noffnal homocysteine level (> 15 pmol/L) had babies with average birth weight 2.2 kg.
Eighty percent of the babies born to hyperhomocysteine- mic mothers were of low birth weight as opposed L0% of the babies born to mothers with nofinal homocysteine level.The risk of delivering a low birth weight baby by pregnant women with hyperhomocysteinemia was nearly 40(95% of cI : 11.5 -126.4) times higher than thatby the mothers with nonnal homocysteine.This is in line with the studies done by Lindblad et aLtz and Vollset et al5.
Another study done by Yajnik et a113 in India reported the higher plasma tHcy concentrations were associated with lower birth weight.Murphy and associatesT in their study demonstrated that neonates of mothers in the highest tHcy tertile at 8 weeks of pregnancy had 3-fold (oR: 3.26;95% 3.65; 95% CI: 1.15, 1 1 .56)higher risk of giving birth to a neonate in the lowest birth weight tertile.Neonates of mothers in the highest tHcy tertile at labor weighed on an average 228 g less than those of mothers in the low and medium tertiles.They also showed that supplemented (with folate and vitamin Bl2) mothers had lower tHcy at labor than unsupplemented mothers, as did their neonates.
Maternal and fetal tHcy was significantly correlated throughout the study.Neonates of mothers in the highest tertile of homocysteine weighed less.Supplemented mothers had lower tHcy at labor than unsupplemented mothers, as did their neonates.These findings are also consistent with findings of the present study where plasma homocysteine level of pregnant women and birth weight of neonates exhibited an inverse relationship indicating thathigher the level of homocysteine the lower is the birth weight (r --0.326, p ( 0.001).
Shirin and associates'o in an attempt to find the associa- tion between plasma Hcy in pregnant women and IUGR enrolled 80 pregnant women with 30 having fetus with IUGR (case) and 50 without IUGR (control).Maternal Hcy of all the subjects were measured at 3'd trimester and its effects on neonatal size were anaLyzed.The maternal Hcy of the IUGR cases was significantly higher than the controls.The IUGR babies born to cases had a signifi- cantly lower birth weight compared to the babies born to control mothers.The study concluded that raised homo- cysteine might be one of the risk factors for IUGR.In a prospective population-based study conducted near Pune (PMNS) between 1993-96, serum homocysteine level was measured in mothers of full-term small for gestational age (SGA) babies (< 10'h centile) and in mothers of appropri- ate for gestational age (AGA) babies (> 10th centile).Mothers of SGA babies were lighter and shorter than plasma tHcy concentration (p < 0.01).Total homocysteine concentrations were inversely related to plasma vitamin Bl2 and red cell folate concentrations (r --0.5, p < 0.01, both).Higher maternal plasma tHcy concentration was significantly associated with lower offspring birth weight (r --0.28, p < 0.05 adjusting for maternal height, weight, gestation at delivery and the baby's gender).This effect was reduced by adjustment for red cell folate concentration.
Other investigators also showed that mothers of SGA babies had higher plasma homocysteine concentrationls,l6.It frdy, therefore, be important to look into the potential role of vitamin B 12 defrciency in elevating plasma homocysteine (Hcy) levels in pregnancy, and its implications for adverse pregnancy outcomes including low birth weight.Methionine synthase is an efizyme which catalyzes the methylation of homocysteine to methionine using vitamin Bl2 as a cofactor and methyltetrahydrofolate as a substrate6.
Formation of methionine through this pathway represents an important component of the one-carbon metabolism for synthesis of phospholipids, proteins, myelin, catecho- lamines, DNA and RNA.A deficiency of either vitamin Bl2 andlor folic acid is likely to affect this pathway resulting in an elevation of plasma Hcy with a relatlely low methionine level.
One of our weaknesses in this study is the failure of mater- nalBL2 and folic acid stafus assessment because of finan- cial constraint.If we could do the cord blood assessment of BI2, folic acid and Hcy, probably it would make out much better pathophysiological picture over this issue.We are optimistic that, in spite of these shortcomings the conclusions derived form this study on our population at least has given a tangible pulse of this big health problem and has created the window to visuaLtze and conceptualize the magnitude of the problem.
The study concludes that pregnant women with elevated plasma total homocysteine carry much higher risk of giving low birth weight babies than the women with nofinal or low level of total homocysteine.Thus, measur- irrg total homcysteine during pregnancy is of much clinical importance as colrective measure could be taken to avert the adverse pregnancy outcome.

Table - I
Comparison of demographic features between case and