Below What Hemoglobin Concentration in Pregnancy is there an Increased Risk of Maternal or Fetal Adverse Effects?

Objectives: To identify the lowest hemoglobin concentration (Hb) associated with increased risk of maternofetal complications. Material and methods: This cohort study was conducted in the Yaoundé University Teaching Hospital, Cameroon, from March 1st, 2011 to February 28th, 2013. Maternal and fetal outcomes among anemic women (AW) and non-anemic women (NW) were compared. Two hundred and twelve AW (booking Hb <10g/dl) without any chronic diseases, carrying singletons and 212 similar NW (Hb ≥11g/dl) were followed up. Main variables were booking and 36 weeks Hb, complications observed and birth weight (BW). Data were analyzed using SPSS 18.0. Fisher exact test and t-test were used for comparison. Level of significance was P<0.05. Results: Mean booking Hb was 8.9 ± 1.1 g/dl among AW against 11.7 ± 0.6 g/dl among NW (P<0.001). Complications of anemia in pregnancy in our series [low BW (RR 7, 95%CI 1.6-30.4), pre-eclampsia (RR 3.3, 95%CI 0.9-11.9) and premature delivery (RR 3, 95%CI 0.6-14.6)] occurred frequently when mean 36 weeks Hb was <9g/dl. Conclusion: Complications were significantly observed when mean Hb was persistently <9g/dl. Correspondence to: Dr. Elie Nkwabong, P.O. Box 1364 Yaoundé, Cameroon, Tel: (237) 699663843, Fax: (237) 222312567, Email: enkwabong@yahoo.fr


I-Introduction
Anemia in women is defined as hemoglobin concentration (Hb) <12 g/dl. Because of physiologic hemodilution observed during pregnancy, World Health Organization (WHO) defines anemia in pregnancy (AP) as Hb <11 g/dl during first trimester 1,2 or Hb <10.5 g/dl in the second trimester 2 . This definition is not being applied by all authors. For some, AP refers to Hb <10 g/ dl during the whole pregnancy. 3,4 Because no studies found any significant maternal nor fetal risk when maternal Hb was ≥10g/dl 5,6 and because hemodilution can start earlier and can be so marked in some pregnant women, AP in our setting is defined as Hb concentration <10 g/dl. When uncorrected, AP is associated with increased risk of intra uterine growth restriction (IUGR), intra uterine fetal death (IUFD), pre eclampsia, preterm delivery, stillbirth and low birth weight (LBW). [6][7][8] According to the WHO definition, prevalence of AP varies between 15% and 67% worldwide with one of the highest (30-65%) in sub-Saharan countries 7,9,10 and the lowest rate (15-25%) in developed countries. 2 Complications of AP depend on its severity. Anemic pregnant women are more prone to death from post partum hemorrhage. It is estimated that 6.37% of maternal death in Africa are anemia attributable maternal mortality whether from direct or indirect cause. 11 Some studies showed that the above mentioned maternal and fetal complications are observed when Hb is less than 9 g/dl. 5 In our country, no study has established above what Hb concentration there are no significant complications of anemia either maternal, fetal or neonatal. The aim of this study therefore was to identify the cutoff point of hemoglobin concentration in pregnancy under which these complications occurred frequently.

III-Results
During the study period, we received 235 anemic women (Hb concentration <10g/dl) with singleton pregnancies out of 4150 women giving an incidence of Mean gestational ages at booking was 19.5 ± 7.3 weeks and ranged from 6 to 34 weeks among AW as against a range of 6 to 29 weeks with a mean of 17.8 ± 4.9 weeks among NW (P=0.0051).
Hb concentration at booking varied between 3.4 and 9.9 g/dl with a mean of 8.9 ± 1.1 g/dl among AW as against a range of 11.0 to 14.1 g/dl with a mean of 11.7 ± 0.6 g/dl among NW (P<0.0001) ( initially AW compared to a range of 11.0 to 13.5 g/dl with a mean of 11.9 ± 0.6 g/dl among NW (P<0.0001) (   Complications noticed during pregnancy were LBW, premature delivery and pre-eclampsia (Table 3).

IV-Discussion
The incidence of anemia (Hb concentration <10g/dl) in our study (5.66%) is lower than that of 8.6% reported in Israel. 3 Gestational age at booking for AW (19.5 weeks) was higher than that of NW (17.5 weeks) (P=0.0051). Some of these anemic women started consultation so late that hemodilution might be so advanced aggravating pre-existing anemia or could have been solely responsible for the anemia (physiologic).
Among AW, mean Hb concentration was 8.9 ± 1.1 g/dl at booking as against 10.8 ± 1.2 g/dl at 36 weeks (P<0.0001). Iron therapy in pregnancy has been shown to improve Hb concentration among anemic women. 12,13 Although iron therapy improved maternal Hb concentration at term, term Hb concentration was significantly lower among AW than among the control group despite treatment with iron and folic acid (P<0.0001). This signifies that, to reduce the prevalence of anemia in pregnancy at term, anemia should be treated before women get pregnant.
When we considered gestational age at delivery, women with booking Hb concentration <10g/dl had increased risk of preterm delivery than those with Hb concentration ≥11g/dl (RR 3, 95%CI 0. 6-14.6). This is due to the fact that anemia with resulting hypoxia can induce maternal and fetal stress, which stimulates the synthesis of corticotropin-releasing hormone (CRH).
Elevated CRH concentrations are a major risk factor for preterm labor, pregnancy-induced hypertension and eclampsia, and premature rupture of the membranes. 14 Our rate of premature delivery among anemic pregnant women (2.8%) was lower than that of 4.1% reported by others. 8 Furthermore, our rate of pre-eclampsia/ eclampsia (4.7%) was also lower than that of 7.3% observed elsewhere. 15 In our series, the rate of IUGR appreciated by the term born LBW rate (8/212 or 3.8%) was similar to than that reported elsewhere. 6 Our study showed that when

V-Conclusion
This study found that maternal and fetal adverse effects of anemia in pregnancy are commonly observed when mean Hb concentration is persistently <9g/dl.
Nevertheless, we think that a Hb value <10g/dl should not be tolerated because antepartum hemorrhage or hemorrhage during vaginal or cesarean delivery is unpredictable and might be life threatening in women whose Hb concentration is 9g/dl or slightly above.