Malaria in pregnancy: ultrasound studies of fetal growth

Abstract

Malaria has been a plague for human mankind. Each year roughly 125 million pregnancies are at risk for malaria infection. This thesis demonstrates the detrimental effects of malaria in pregnancy on the mother and the baby. To determine the effects of malaria in pregnancy on birth outcomes, accurate pregnancy dating is required and newborn babies weighed precisely. In most malaria endemic areas, antenatal ultrasound, the gold standard for pregnancy dating, does not exist as a result of shortage of machines and qualified sonographers. In the antenatal clinics of the Shoklo Malaria Research Unit on the Thai-Burmese border, local health workers were successfully trained in antenatal ultrasound and midwifes schooled in safe deliveries. In this thesis the promising results of quality assessments are described in fully. Antenatal ultrasound is proposed as a very useful tool for broadening our understanding of adverse fetal growth effects associated with malaria in pregnancy. Reference equations for fetal biometry and birthweight for gestational age were created, which were used for clinical practice and for further analysis of the effect of malaria in pregnancy on fetal growth. Pregnant women and local staff recognized antenatal ultrasound as an acceptable tool and described the benefits they perceived in terms of safety of pregnancy. Malaria in pregnancy was associated with growth restriction across the range of viability in this population. Accurate gestational age assessment, measured by ultrasound, and population centiles, permit differentiation of low birthweight from preterm birth and small for gestational age: low birthweight is a poor predictor of small for gestational age newborns. Despite early treatment in all positive women, one or more (a)symptomatic P.falciparum or P.vivax malaria infections in the first half of pregnancy resulted in a smaller than expected mid-trimester fetal head diameter. In a prospective followed group of pregnant women at risk for malaria with frequent ultrasound, there were no stillbirths and only one case of severe malaria. However, malaria infection in the second trimester was associated with a reduction of fetal head growth, but there was no difference in birthweight centiles between malaria and non-malaria pregnancies. The need for longitudinal analysis of this data, to detect a recovery of growth is highlighted. The new technique of 3D ultrasound volumetry of the placenta was used to improve our understanding of the pathophysiological constraints on fetal growth caused by malaria infection in early pregnancy. Most placental volumes of women who were infected with P.falciparum malaria before the volumes scan were below the 10th centile. There were no gross effects detected in fetal brain development between 22 malaria infected (but immediately treated) and 22 matched, but non infected pregnancies. Close monitoring of pregnant women and prompt treatment of any malaria episode with efficacious drugs minimizes the negative effects of malaria on fetal growth. Governments should encourage the value of antenatal care, early detection and treatment of malaria in pregnancy and correct use of antenatal ultrasound in malaria endemic countries.