Date of Award
2024
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Master of Medical and Health Science by Research
School
School of Medical and Health Sciences
First Supervisor
David Coall
Second Supervisor
Julie Sartori
Third Supervisor
Julie Quinlivan
Fourth Supervisor
Anna Callan
Abstract
Human placentae are increasingly being recognized as important biospecimens that have the potential to indicate the health disposition of mother and child. Variations in placental morphology may be reflected in placental parameters that include: placental weight, length, diameter, thickness, surface area, and eccentricity of the umbilical cord insertion site. Variations in placental morphology have been associated with pregnancy challenges such as pre-eclampsia, diabetes, and poor maternal nutritional status. It is believed the changed morphology is the placentas attempt to compensate for the poor maternal conditions.
Ultimately, if the physiological challenges are severe, they may impact the fetal phenotype. Altered placental morphology is linked to an increased risk of developing diseases (especially cardiovascular) later in life. This ability for the intrauterine environment to modulate the fetal phenotype, can have life-long consequences, and is known as the Developmental Origins of Health and Disease hypothesis (DOHaD).
This study investigated the association between maternal blood pressure (BP) during pregnancy and gross anatomical placental measures in a West Australian cohort. Data was extracted from the Placenta Project database at Edith Cowan University (ECU). Data included maternal and offspring clinical data, maternal health questionnaires, and placental data (including digital images). Sequential maternal BP was examined and analysed in relation to the placental morphological features. These placental morphological features were derived from existing manual measures and extrapolated from digital image examination performed by the primary author.
In this research BP cohorts included systolic BP (SBP), diastolic BP (DBP) and pulse pressure (PP) which were grouped into low, middle and high BP cohorts. In addition a Tension variable, was grouped into Hypotension, Normotension and Hypertension. In all MLR models there were weakly significant (p= < 0.100) differences between the cohort most likely to have greatest values, and the cohort likely to have lowest values for all variables except smoking status and volume of cigarettes per day (pre-pregnancy). Although these two variables had limited significance in the Tension MLR they added to the overall significance of the MLR, suggesting a confounding influence.
Important research findings included Hypotensive and Low SBP cohorts having at least weakly significantly (p= < 0.100) association with male neonates compared to Normotensive and middle SBP who were associated with female neonates. While not always significantly different, the Hypertensive and high SBP cohorts were more likely to have male neonates than middle BP cohorts, and less likely than low BP cohorts.
Along with neonatal gender, there were several placental variables that were unique to, or had unique associations with the Tension MLR. This lends support to the theory that placental dysfunction, or at least variation, is linked to Hypertension. There are also unique associations with Hypotension, leading to the possibility that Hypotension also has unique placental involvement including tension-specific associations to placental weight (untrimmed), and unique associations with placental width.
The placentae of expectant women with Hypertension, had a lighter, shorter length (X-axis) and width (Y-axis), placenta with middle area and roundness was further associated with an increased mean depth and Feret’s diameter. This may suggest increased apoptosis, or inhibition of early growth with compensatory growth in latter pregnancy. This compensation appears to be insufficient as the Hypertensive neonates in this study, were associated with a shorter gestational age, lighter weight, and a lower 1min APGAR.
The Hypotensive placentas were found to be the heaviest, widest, of greatest surface area, with the shortest Feret’s diameter., They were also documented as having the least roundness and middling length and the thinnest mean depth. In a curious dichotomy with Hypertension, the Hypotensive placentae seemed to be very efficient, producing the longest gestational age, longest length, and best APGAR at 1 min neonates. While this may indicate increased placental efficiency, there could also be a potential for survivors bias with Hypotensive pregnancies.
Length (X-axis), width (Y-axis) and Feret’s diameter may be influenced by SBP and PP, and as a result reflected in tension conditions. The significant (p= < 0.050) association with shorter placental lengths (X- and Y-axis) and higher BP measures suggested an increased apoptosis, inhibition to placental expansion, and/or a potential ‘sensing’ of sufficient substrate availability. If the placenta can sense substrates, a high availability may result in withholding from further expenditure toward early placental expansion. Meanwhile lower BPs were significantly (p= < 0.050) associated with longer length (X-axis) and width (Y-axis), potentially suggesting a reduced apoptosis, inhibition of lateral expansion, and/or an increased drive for the placenta to ‘search’ for substrates. Hypotension showed a unique deviation concerning placental length (X-axis) that might implicate a direct association that was not reflected in low SBP.
Placental mean depth was associated with Tension MLR, and uniquely, had highly significant (p= < 0.050) differences between all cohorts. The relationship showed a linear pattern with Hypotension more likely to have a lower mean depth. This may suggest that placental depth is strongly affected by Hypotension and/or Hypertension conditions.
Placental weight (untrimmed) was also differentially affected by Tension disorders of Hypotension and Hypertension. In the multinomial logistics regression (MLR’s) of SBP and PP the linear relationship had lightest weight (untrimmed) significantly (p=< 0.050) associated with the low BP’s. Conversely, lightest weight (untrimmed) was significantly associated with Hypertension. This suggests that the placental disfunction of Hypertension and Hypotension have a direct effect on placental weight that opposes that of ‘normal’ SBP associations.
Placental roundness was a novel measure of this research that showed a parabolic association to Tension and PP with middling BP’s significantly (p=< 0.050) associated with roundest placenta. Meanwhile the association in the DBP MLR there was a significantly rounder placenta in high DBP, with a linear pattern. Suggesting that DBP may play a key role in the placenta’s ability to optimally grow into the space created by a fitted ellipse. Meanwhile deviations away from middling Tension and PP cohorts result in lower roundness.
This research extends our understanding of maternal blood pressure and placental development during gestation, including the novel variables of Hypotension, and placental roundness.
DOI
10.25958/0ykg-0v45
Access Note
Access to this thesis is embargoed until 23rd January 2027
Recommended Citation
Cannon, M. D. (2024). Maternal blood pressure during pregnancy and placental gross anatomy in a cohort of West Australian pregnancies. Edith Cowan University. https://doi.org/10.25958/0ykg-0v45
Included in
Female Urogenital Diseases and Pregnancy Complications Commons, Obstetrics and Gynecology Commons