Pregnancy Clinical Trial
Official title:
Water Immersion and Changes in the Fetoplacental Circulation. A Case-Control Study With the Case as it's Own Control.
Pregnant women with pre-eclampsia and growth restricted fetuses often have a reduced
function of the placenta. This is accompanied by an increased perinatal mortality and
morbidity.
By ultrasound it is possible to measure blood flow and vascular resistance in both the fetal
umbilical cord and in the blood vessels supplying the uterus. A high resistance in these
vessels occur before the child is severely affected.
By immersion in water extracellular fluid is redistributed back into the circulation, and
central blood volume increases. Previous studies have shown that maternal minute-volume
increases, while blood pressure drops slightly. Also an increased amniotic fluid has been
recorded. This has been interpreted as an expression of increased renal blood flow.
Immersion into water could increase blood flow in the vessels supplying the uterus and thus
increase blood flow to the child.
The investigators aim to clarify this by examining blood flow and resistance in the blood
vessel supplying the uterus and in the umbilical cord, while the participant is immersed
into water. Initially, 25 healthy women with an uncomplicated singleton pregnancy recruited
from the Department of Obstetrics and Gynaecology: Hvidovre University Hospital, Denmark,
will be examined. The participant will act as its own control and measurements above water
and immersed will be conducted at the same study session.
Ultimately the investigators seek to contribute to a non-invasive option for prolonging
those pregnancies where the fetus and/or maternal condition requires delivery several weeks
before term, and where immersion of the pregnant woman in the water a few hours one to
several times daily, may prolong the pregnancy the required number of hours/days for
antenatal steroid treatment to be sufficient.
There are no risks associated with the study and the project team considers it ethical to
implement this. The study is not supported by pharmaceutical companies or other groups with
economic interests. The project group itself has taken the initiative to study.
Intrauterine growth retardation and preeclampsia are major causes of neonatal mortality,
morbidity and later neurological sequelae. The conditions are associated with an increased
resistance to blood flow in the placenta, that can be detected by an increase in pulsatility
index (PI) in the umbilical artery (1).
When Doppler flow is assessed in the uterine arteries, increased resistance in the
uteroplacental circuit is indicated both by an increase in PI and by a change in the flow
velocity waveform, which can be seen as a "notch" in early diastole.
In the 2nd trimester, the invasion of trophoblasts and the remodeling of the uterine spiral
arteries are complete. Persistence of a bilateral notch beyond the 24th week of gestation is
associated with an increased risk of intrauterine growth retardation and preeclampsia. Even
though the risk persists, the notch usually disappears later in pregnancy (2).
When the non-pregnant body is immersed in water, extracellular fluid is redistributed back
into the circulation. Central blood volume, cardiac output, renal perfusion and urine output
increase and the blood pressure falls (3-7).
The same changes occur in the pregnant women. However the increased diuresis is strongly
correlated with the degree of the pregnancy edema, which decreases substantially (8), and
the amount of amniotic fluid increases (9). The changes all occur within minutes (8), but
are transient and return to conditions before immersion within 1-2 hours after the pregnant
woman has come out of the water.
The changes in the above parameters are significant but less pronounced in pregnant women
with preeclampsia than in pregnant women without the condition (11). None of the experiments
showed changes in the fetal heart rate.
Because of the physiological changes that take place when pregnant women are immersed in
water, several authors have speculated whether immersion has a positive effect on the
uteroplacental circuit (8,10,12).
There are no published data on Doppler flow measurements in the umbilical artery and the
uterine arteries during water immersion.
The aim of the present study is to evaluate the effect of immersion on the fetoplacental and
uteroplacental circuits in healthy pregnant women, using Doppler flow measurements in the
umbilical artery and uterine arteries.
Materials From the Department of Obstetrics and Gynecology, Hvidovre University Hospital,
Denmark, we recruit 25 healthy women with an uncomplicated singleton pregnancy. Gestational
age was between 26 and 38 weeks. All participants will have a normal first trimester
combined screening and a normal second trimester ultrasound scan for fetal abnormalities.
Within the last 2 weeks prior to participation, fetal weight will be estimated, and only
woman with fetuses of normal weight (within the 95 percentile) will be included.
Methods The study is performed at the labor ward at Hvidovre Hospital, Denmark. If fetal
weight has not been estimated by an ultrasound examination within the last 2 weeks, fetal
weight will be estimated on the day of the study. In order to exclude an on-going infection,
the temperature is measured and the urine examined in all participants on the day of the
study.
The same experienced sonographer performs all examinations, and the same Bruel & Kjaer
ultrasound scanner, suitable for scanning under water, is used in all participants.
Each participant has five recordings of blood pressure, pulse, saturation, deepest vertical
pocket (DVP) of amniotic fluid and Doppler flow in the umbilical artery and uterine
arteries. All recordings are obtained during the same study session. Doppler ultrasound
measurements of umbilical and uterine arteries are obtained by pulsed wave ultrasound using
an insonating angle as close to 0 degrees as possible. The Doppler measurements on the
uterine arteries are obtained approximately one centimeter from the crossing of the iliac
arteries. The pulsatility index (PI) is calculated automatically by the machine using the
formula (systolic velocity-diastolic velocity)/mean velocity. PI of the uterine artery is
calculated as the mean PI of the left and the right uterine artery.
For immersion, a regular bathtub is used. The tub is filled with thermo-neutral tap water
(35.0 °C +/- 0.5 °C). The temperature of the water is measured every 10 minutes, and kept
thermo-neutral during the period of immersion.
The participants are placed in a supine position outside the bathtub and the first
recordings are obtained (T0). Afterwards the participants are immersed in water, placed in a
supine position, and measurements are repeated after 5 min (T5) and 25 min (T25) in water.
All measurements are repeated with the participant in a supine position outside the bathtub
15 min (T40) and 30 min (T55) after immersion.
All recordings of Doppler flow curves and measurements of amniotic fluid (DVP) are saved on
an USB stick. An experienced specialist in fetal medicine, who is not present at the
investigation, validates each recording blindly. Any recording not eligible for approval is
redefined as a missing value.
Statistical analysis Because the measurements taken before, during and after immersion, are
made in the same patient during the same study session, and with the same ultrasound
apparatus, each participant act as their own control.
Data are expressed as means +/- standard error of the mean (SEM). The first recording, T0,
was defined as baseline. Comparisons between the respective recordings, T0-T55, are done
using a two-tailed paired t-test on raw data. P-values < 0.05 are considered significant.
For calculation, STATA 12.1 (13) is used.
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Endpoint Classification: Safety/Efficacy Study, Intervention Model: Single Group Assignment, Masking: Single Blind (Outcomes Assessor), Primary Purpose: Treatment
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