Syphilis in Pregnancy: Experience From a Rural Aboriginal Community
Authors: How John H. Y. , Bowditch John D. P. 
Published: February 2008

EDITORIAL COMMENT: We accepted this paper for publication because a 28% incidence of syphilis (20 of 71 pregnancies) in any Australian community deserves attention. The authors' analysis of this large series of cases presents the problems of screening and the need for rescreening in certain communities. This series is large enough to focus upon whether or not syphilis is a cause of pathological enlargement of the placenta. Before the discovery of the rhesus factor it was stated in many publications that congenital syphilis was associated with a ‘pale, bulky, greasy‐looking placenta’ (A). In Melbourne, museum pathology pots that contained such examples of large placentas labelled as due to syphilis were found on reexamination to be cases of erythroblastosis.

What is classical is not necessarily what is most common! Even in erythroblastosis due to maternal rhesus isoimmunization, a condition in which placental enlargement is totally accepted, the placental weight exceeded 700 g in only 37of 257cases associated with a direct Coombs positive cord blood in one reported series (B). Erythroblastosis was the main cause of really huge placentas at least until recently when intrauterine transfusion was introduced, and in this series 17 of the 257 weighed more than 1,000 g and 7 (2.7%) weighed more than 1,500 g (this paper reported upon the various causes of large placentas (in singleton pregnancies) and diabetes mellitus was the only other cause of a placental weight above 1,500 g (3 of 180 cases)).

In the present study the only placenta above the 90th percentile was not associated with syphilis. Table 1 shows that the largest placenta in the plasma reagin positive cases weighed 775 g. For comparison we calculated the 50th percentile for placental weight (untrimmed of membranes, weighed wet after removal of any attached blood clots) in 5,000 consecutive singleton pregnancies with confinements at the Mercy Hospital for Women in 1990; the figure was 580 g and the 90th percentile was 750 g, and the 10th percentile 430 g.

There are conflicting authoritative accounts in the literature concerning placental size in congenital syphilis. Benirschke and Kaufman (C) quote a number of authors who stated that placental enlargement was a feature of congenital syphilis and that massive placental enlargement may occur with a macerated fetus. Nabarro considered that placental enlargement occurred in syphilis only when the fetus was macerated (A).

Galan et al recently reported a case of syphilis diagnosed at 24 weeks' gestation where ultrasonography revealed fetal hydrops and placental thickening which resolved progressively over 3 weeks (serial ultrasonography) with intravenous infusion of penicillin G to the mother (D).

Summary: Syphilis in pregnancy is seldom encountered in urban Australia. This retrospective study reports on the high prevalence of syphilis and its associated complications in a group of pregnant Aboriginal women attending the Dareton Community Health Centre for antenatal care between September, 1989 and September, 1991. During this time, the centre provided antenatal care for 71 Aboriginal pregnancies and maternal syphilis was found in 20 (28%). The mean age of the women was 21.3 years (range of 14–33 years). The perinatal mortality rate was 48 per 1,000 births. All stillbirths were associated with maternal syphilis. The relative risk of stillbirth in the presence of syphilis was 4 (95% CI 2.56‐6.25, p = 0.022). Prematurity was associated with maternal syphilis. The odds ratio for premature delivery was 21.5 (95% CI 2.26‐2.05, p = 0.003). There was no statistical difference between the mean birth‐weight and mean placental weight of term infants born to women with syphilis and women without syphilis (p = 0.35 and p = 0.31 respectively). When the placentalrbirth‐weight ratios were considered, an apparent larger placenta was seen in association with syphilis but this was secondary to the lower birth‐weights in association with prematurity. Late and poor attendance for antenatal care was a feature of all women attending this centre and not a feature associated with syphilis. The treatment and follow‐up of syphilis were hindered by poor compliance.