Oral Presentation 46th Annual Meeting of the Fetal and Neonatal Physiological Society 2019

Sex differences in cerebro:placental and umbilico:cerebral ratios: A longitudinal study (#12)

Ganesh Acharya 1 2 , Cathrine Ebbing 3 , Henriette O Karlsen 3 , Torvid Kiserud 3 , Svein Rasmussen 4 , Juha Rasanen 5
  1. Karolinska Instititet, Stockholm, -, Sweden
  2. Department of Clinical Medicine , UiT- The Arctic University of Norway, Tromsø, -, Norway
  3. Department of Obstetrics and Gynecology , Haukeland University Hospital, Bergen, -, Norway
  4. Department of Clinical Science, University of Bergen, Bergen, -, Norway
  5. University Hospital, University of Helsinki, Helsinki, Finland

Introduction:

Studying relative distribution of fetal cardiac output to the placenta and brain could provide valuable information on fetal circulatory adaptation to adverse in utero conditions. In clinical practice, the ratios of Doppler-derived umbilical (UA) and middle cerebral (MCA) arterial pulsatility indices (PI) are commonly used to identify the “brain sparing” phenomenon while monitoring fetuses at risk of adverse perinatal outcome. However, reference values used for this purpose do not take into account sex-differences.

Our objective was to evaluate gestational age specific sex differences in cerebro-placental (CPR) and umbilico-cerebral (UCR) ratios and construct appropriate reference charts.

 

Methods:This was a prospective longitudinal study of singleton low-risk pregnancies. Doppler blood velocity waveforms were obtained serially from the UA and MCA during 19-41 weeks of gestation, and PIs were calculated. CPR and UCR were calculated as the ratios, MCA PI/ UA PI and UA PI/ MCA PI, respectively. The outcome of pregnancies was recorded. Sex of the fetus was determined after delivery. Reference intervals were constructed using multilevel modelling and gestational age-specific Z-scores of male and female fetuses were compared.

 

Results:Of a total of 299 pregnancies enrolled, 284 women and their fetuses (148 male and 136 female) were included in the final analysis, and 979 paired measurements of UA and MCA PIs were used to construct sex-specific reference intervals. Both CPR and UCR had U-shaped curves of development during pregnancy, but with opposite directions. There was a small but significant (P=0.007) difference in z-scores of CPR and UCR between male and female fetuses throughout the second half of pregnancy.

 

Conclusions: Sex-specific longitudinal reference ranges of CPR and UCR provide clinicians the possibility to refine serial assessment of fetuses at risk of adverse perinatal outcome. As the magnitude of sex-difference was small, the clinical significance of such refinements needs further evaluation.