Polymorphism in the ADRB2 gene explains a small portion of intersubject variability in pain relative to cervical dilation in the first stage of labor.
BACKGROUND
Variability in labor pain has been associated with demographic, clinical, and psychological factors. Polymorphisms of the β2-adrenergic receptor gene (ADRB2) influence sensitivity to experimental pain in humans and are a risk factor for chronic pain. The authors hypothesized that polymorphisms in ADRB2 may influence labor pain.


METHODS
After Institutional Review Board approval and written informed consent, the authors prospectively obtained hourly pain reports from 233 nulliparous parturients during the first stage of labor, of which 199 were included in the current analysis. DNA from blood samples was genotyped at polymorphisms in the genes for the β2-adrenergic receptor, the μ opioid receptor subtype 1, catechol-O-methyltransferase, fatty acid amide hydrolase, and the oxytocin receptor. Labor pain as a function of cervical dilation was modeled with previously described methods. Patient covariates, ADRB2 genotype, and obstetrical and anesthesia treatment were evaluated as covariates in the model.


RESULTS
Labor pain more rapidly became severe in parturients heterozygous or homozygous for the G allele at rs1042714 in the ADRB2 gene. Labor pain increased more rapidly after artificial rupture of membranes, augmentation with oxytocin, and in younger women. Inclusion of covariates explained approximately 10% of the variability between subjects. ADRB2 genotype explained less than 1% of the intersubject variability.


CONCLUSIONS
ADRB2 genotype correlates with labor pain but explained less than 1% of the intersubject variance in the model.
From the Department of Anesthesiology, King Fahad Medical City, Riyadh, Saudi Arabia, and Department of Anesthesiology, University of Virginia, Charlottesville, Virginia (A.S.T.); Department of Anesthesiology, Columbia University, New York, New York (W.M.J.); Department of Obstetrics and Gynecology, Women's Specialized Hospital, King Fahad Medical City, Riyadh, Saudi Arabia (S.H., R.T.); and Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University, Stanford, California (P.F.).
Abdullah S
AS
Terkawi
William M
WM
Jackson
Shehnaz
S
Hansoti
Rabeena
R
Tabassum
Pamela
P
Flood
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D016362:Analgesia, Obstetrical; D000773:Anesthesia, Obstetrical; D002584:Cervix Uteri / Q000502:physiology*; D004247:DNA / Q000235:genetics; D036861:Delivery, Obstetric; D005260:Female; D006801:Humans; D007747:Labor Stage, First / Q000235:genetics / Q000502:physiology*; D015233:Models, Statistical; D010120:Oxytocics; D010121:Oxytocin; D010146:Pain / Q000235:genetics* / Q000503:physiopathology*; D010147:Pain Measurement; D011110:Polymorphism, Genetic; D020641:Polymorphism, Single Nucleotide; D011247:Pregnancy; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics*; D012529:Saudi Arabia / Q000453:epidemiology; D012959:Socioeconomic Factors; D055815:Young Adult
D010120:Oxytocics; D018343:Receptors, Adrenergic, beta-2; D010121:Oxytocin; D004247:DNA