A longitudinal study of splenomegaly in pregnancy in a malaria endemic area in Papua New Guinea.

582 pregnant women living in a defined population were examined for splenomegaly when attending monthly rural antenatal clinics in Madang Province, Papua New Guinea, in an area with all-year malaria transmission. 712 non-pregnant women of child-bearing age from the same population were examined as controls. In non-pregnant women who later became pregnant spleen rates increased in early pregnancy. Peak spleen rates in early pregnancy occurred before 16 weeks gestation for all gravida classes. There was a decrease in spleen rate and a fall in average enlarged spleen size with increasing gestational age for women attending on a first clinic visit and before receiving chloroquine prophylaxis. It is suggested that pregnancy induces a change in splenic function early in gestation, which in primigravidae results in increased frequency of Plasmodium falciparum parasitaemia. In multigravidae these early gestational spleen changes did not predispose to parasitaemia, which indicated that these women had developed enhanced malaria immunity. There was a significant rise in spleen rates with rising parity in non-pregnant women with a peak rate at parity 3. This rise is considered to relate to responses induced by pregnancy in the first and second pregnancies. Weekly chloroquine prophylaxis increased the frequency of splenomegaly in pregnant women attending for 3 consecutive months, indicating that chloroquine had biological activity on the splenic immune response in vivo.