THE EFFECTS OF MODE OF DELIVERY AND SEX OF NEWBORN ON PLACENTAL MORPHOLOGY IN CONTROL AND DIABETIC PREGNANCIES

Placentae from control and diabetic subjects were analysed using stere ological techniques in order to assess the effects of mode of delivery (vaginal versus caesarean) and sex of neonate on parenchymal morpholo gy. Effects were assessed using indices of peripheral villous and feta l capillary growth, villous maturity, extent of maternal intervillous space and thickness of intervascular tissue layers. Placentae were fro m pregnancies (37-42 wk) which were either uncomplicated (control grou p) or complicated by diabetes mellitus (diabetic group, White class D) which was reasonably well controlled in terms of glucose and glycated haemoglobin levels. Neonatal and placental weights were recorded and placentae sampled in a systematic random fashion. Fields of view on fo rmalin-fixed, paraffin-embedded sections were analysed to obtain estim ates of volumes, surface areas, lengths and diffusion (harmonic mean) distances. Comparisons were drawn using 3-way analyses of Variance wit h group, mode of delivery and sex as the principal effects. The mean l ength of gestation was 2 wk longer in controls (39 Versus 37 wk). Desp ite this, mean birth weight was similar (3.5 kg) in control and diabet ic groups. Moreover, diabetic placentae were 17% heavier and showed sh orter fetal plasma distances (30 %) and larger fetal capillaries (volu me 45 %, surface 39 % and length 30% greater). Mode of delivery had si gnificant main and interaction effects on stromal diffusion distance ( 25 % greater in vaginal deliveries) and an interaction effect on fetal capillary volume. Sex had significant main effects on the maternal pl asma distance (21 % greater in males) and capillary volume (30 % bigge r in males) and an interaction effect on placental weight and mean cap illary diameter. Gestational ages did not vary between modes of delive ry or sex of newborn. Our results are consistent with some but not all of the earlier findings on the effects of diabetes and mode of delive ry. They indicate that morphological changes in diabetes are associate d with fetal hypoxia and influence appropriate-for-age as well as larg e-for-age deliveries. Finally, they emphasise the need to monitor the sex of the neonate when comparing control and diabetic placentae.