Malaria and fetal growth alterations in the 3(rd) trimester of pregnancy: a longitudinal ultrasound study

Abstract

Background: Pregnancy associated malaria is associated with decreased birth weight, but in-utero evaluation of fetal growth alterations is rarely performed. The objective of this study was to investigate malaria induced changes in fetal growth during the 3(rd) trimester using trans-abdominal ultrasound.

Methods: An observational study of 876 pregnant women (398 primi- and secundigravidae and 478 multigravidae) was conducted in Tanzania. Fetal growth was monitored with ultrasound and screening for malaria was performed regularly. Birth weight and fetal weight were converted to z-scores, and fetal growth evaluated as fetal weight gain from the 26th week of pregnancy.

Results: Malaria infection only affected birth weight and fetal growth among primi- and secundigravid women. Forty-eight of the 398 primi- and secundigravid women had malaria during pregnancy causing a reduction in the newborns z-score of -0.50 (95% CI: -0.86, -0.13, P = 0.008, multiple linear regression). Fifty-eight percent (28/48) of the primi- and secundigravidae had malaria in the first half of pregnancy, but an effect on fetal growth was observed in the 3(rd) trimester with an OR of 4.89 for the fetal growth rate belonging to the lowest 25% in the population (95%CI: 2.03-11.79, P<0.001, multiple logistic regression). At an individual level, among the primi- and secundigravidae, 27% experienced alterations of fetal growth immediately after exposure but only for a short interval, 27% only late in pregnancy, 16.2% persistently from exposure until the end of pregnancy, and 29.7% had no alterations of fetal growth.

Conclusions: The effect of malaria infections was observed during the 3(rd) trimester, despite infections occurring much earlier in pregnancy, and different mechanisms might operate leading to different patterns of growth alterations. This study highlights the need for protection against malaria throughout pregnancy and the recognition that observed changes in fetal growth might be a consequence of an infection much earlier in pregnancy.

Figure 1. Different growth patterns after a malaria infection.

The four individual growth patterns are superimposed on a weight chart developed from healthy pregnancies in the cohort . Normal growth observed after an infection at gestational age (GA) 20+1 (panel A). Immediate effect observed after an infection at GA 20+1 with an initial decline in growth observed in the growth interval antenatal visit (ANV)2– ANV3 followed by persistently normal growth until delivery (panel B). Late effect observed after an infection at a GA 17+0 with normal growth until ANV4 and thereafter a decline in growth until delivery (panel C). Persistent effect observed after an infection at GA 19+6 with decline in growth throughout pregnancy (panel D). The solid vertical lines indicate the timing of the three ANV. In panel B the ANV2 occurred slightly delayed at a GA of 27+2. The solid black and grey lines represent the 90^th, 50^th, and 10^th percentile.