The prevalence rate observed in this study is, in contrast, higher than the findings of Oduwole etal57 in Calabar despite the similarity in the definition of congenital malaria for the two studies. The reason for this observation may be difficult to say.
The presence of malaria parasites in the placenta and maternal blood were found to be significantly associated with the occurrence of congenital malaria. This is similar to the findings by Falade et al26 in the multicentre study in Nigeria as well as those by Obiajunwa et al in Ile-Ife.42Placental malaria occurs as a result of sequestration of malaria parasites in the placenta interfering with nutrient transport to the fetus and causing among other things, congenital malaria.
Prevalence rates as high as 80% have been documented,79-81 but the value observed in this study was 57.6%. This is, however, high compared to 14% observed by Mokuolu.90 Similarly, maternal parasitaemia of 42.9% observed in this study is high compared to 17%
documented in his study. These high values may have contributed to the high prevalence rate of congenital malaria observed in this study.
History of fever in pregnancy was also significantly associated with congenital malaria. This is in keeping with the findings by Okafor UH in Enugu, Orogade in Nothern Nigeria, Abiodun 28,44,74 and Lesko in the United States.13 Fever in pregnancy may be a symptom of malaria
infection which causes maternal or placental malaria. These consequently lead to congenital malaria.
Malaria preventive measures remain the priority intervention required to protect the fetus and the newborn against the adverse effects of malaria in pregnancy.123 WHO has recommended a three pronged strategic framework in areas of stable malaria transmission of sub Saharan Africa: IPT, ITN and case management of malaria illness.82 Mothers who, for one reason or the other failed to use ITN were more likely to deliver babies with congenital malaria. Even though up to 77.5% of the participants had heard of ITN, only 19.6% used it at any time in pregnancy. Most of the women attributed failure to use ITN to non availability of ITNs. This finding is surprising considering the fact that most of these women had their antenatal care at the tertiary health care facility and ideally should have had access to free ITNs.
This calls for an evaluation of this important WHO programme in this centre.
The low prevalence of congenital malaria among the women that used anti-malarial prophylaxis observed in this study is similar to that documented by Falade et al.26 According to the WHO protocol for the use of IPT in pregnancy, SP is the recommended drug and should be taken at least twice in pregnancy.79 It was however, observed that the majority of the women took IPT only once which may have contributed
to the high prevalence rate of congenital malaria observed. The fact that majority of the women took IPT only once may be due to late booking and lack of supervision. Ideally, each dose should be taken during antenatal care and under direct supervision of the attending healthcare personnel (Directly Observed Treatment Strategy).
Many researchers that worked on congenital malaria documented a significant relationship between congenital malaria and lower parities.15,26,28,74 This study also buttresses this fact as we observed that babies of the primigravidae had congenital malaria more than those of higher parities. This has been attributed to placental inexperience in the primigravidae, the placentae being a new organ in them.21
No significant relationship was noted between mother’s HIV status and the occurrence of congenital malaria. This is contradictory to the previously known fact that HIV is known to increase placental parasitization and consequently congenital malaria.31,86,104 A higher prevalence of congenital malaria documented in the Nothern states in the study on the epidemiology of congenital malaria in Nigeria, was attributed to the high prevalence of HIV in that region.26 The difference in the documentations may be due to the small number of HIV positive women recruited in this study.
Prematurity did not affect the prevalence of congenital malaria in this study. This is contrary to what was documented in Sagamu by Sotimehin et al and in Karachi by Zafar T where prematurity was identified as the main neonatal risk factor for congenital malaria.15,70 On the other hand, Akindele’s work in 1991 and Abiodun’s work in 2006 tend to agree with our finding.44,72It is important to note however, that these studies, as well as this work, were not primarily powered to detect differences between congenital malaria in preterm and full term babies. Moreover, the number of preterm babies recruited in this study is too small to make a statistical conclusion.
Congenital malaria was seen to have no significant association with fetal anaemia in this study. This is contradictory to the documentation by Falade et al where babies born with congenital malaria had lower hematocrit than those born without (p<0.0001) and the study by Orogade etal where anaemia was found in 15.1% of parasitaemic babies compared to 9.2 of non parasitaemic ones .26,60 The difference may be due to the variation in the cut off point for fetal anaemia or anaemia at birth. While the two researchers used 42% as their cut off point, the researcher used 36.5%.110The significance of this finding may also be limited by the small size of babies with fetal anaemia.
In this study, babies with congenital malaria weighed significantly less than those without. This is similar to the findings of Larkin etal in Zambia.46 Other researchers like Steketee et al and Adebami et al also found a significant relationship between congenital malaria and birth weight.124-5 In contrast however, Falade et al, Omalu et al and Onwuanaku et al did not find any statistically significant relationship between the two, even though babies with congenital malaria had lower mean birth weight than those without.26,126-7 According to Steketee et al, other conditions like maternal nutrition, maternal health condition, birth order, socioeconomic status and maternal stature could also influence birth weight.124 These were however not investigated in this study.
Significant association was seen between congenital malaria and the place of antenatal care which however disagrees with Abiodun’s work and that of Orogade in Kaduna.40,64 The decreased prevalence of congenital malaria among the women that had their antenatal care at the tertiary health facility can be explained by accessibility to proper antenatal education and availability of informed healthcare professionals at the tertiary health care level. On the other hand however, this observation might have been influenced by the fact that all the samples were drawn from the tertiary institution where most of the mothers had their antenatal care.
The level of parasitaemia was generally low and there was paucity of symptoms as only 8.3% of the babies were observed to have one symptom or the other during examination. Only seven of them had persistence of parasitaemia upon referral to SCBU. This is in keeping with what was documented following the multicentre study in Nigeria by Falade et al where most of the babies no longer had malaria parasites after 72 hours.26 All the babies with persistence of parasitaemia were treated with syrup Quinine despite the result of investigation for sepsis. Only two of the asymptomatic babies were seen after discharge from the hospital, both presenting with fever on days 12 and 24 respectively. One had persistence of malaria parasites and was treated with syrup Quinine while the other did not and was eventually treated for sepsis.
None of the parasitaemic mothers became symptomatic before discharge.
CONCLUSION
Congenital malaria is not rare as previously thought, with a prevalence rate of 35.5% observed in this study.
Mothers with placental or maternal malaria parasitaemia are more likely to deliver babies with congenital malaria.
Failure to use IPT and sleep under ITN during pregnancy and history of fever in the last trimester increase the risk for congenital malaria.
Babies whose mothers are primigravidae are more likely to have congenital malaria than those whose mothers are of higher parities.
RECOMMENDATIONS
1. Babies delivered by primigravidae and those with history of fever in pregnancy, especially in last trimester should be screened for congenital malaria.
2. All pregnant women should be encouraged to take IPT at least twice in pregnancy to reduce the risk of congenital malaria in
their babies and for other maternal health benefits.
3. Efforts at increasing awareness on the use of ITN in pregnancy should be intensified and the government should make ITNs available and affordable even if they are not distributed freely.
4. The wide variations in the documented prevalence rates of congenital malaria can be checked by having a standardized definition bearing in mind that some babies with only cord blood parasitaemia can be missed as they may develop symptoms later.
LIMITATIONS
The inability to ensure that the slides were crosschecked systematically by another WHO certified microscopist is an important limitation.
The study was carried out within a short period (two months) and might have influenced the findings. Longer period of study may give a better assessment.
Other methods of diagnosis, like Polymerase Chain Reaction, was not used to crosscheck the parasite negative slides.
Some of the findings on prematurity, maternal HIV and fetal anaemia are relevant but may not be used to draw useful conclusions because of the small sample size involved.
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