Epidural pain relief has major effects on the hormones of labor. It inhibits beta-endorphin production(1) and therefore also inhibits the shift in consciousness that is part of a normal labor. When an epidural is in place, the oxytocin peak that occurs just before birth when the labor has been undisturbed is also inhibited, because the stretch receptors of a birthing woman’s lower vagina, which trigger this peak when stretched by the descending baby’s head, are numbed. This effect probably persists even when the epidural has worn off and sensation has returned. This is because the nerve fibers involved are smaller than the sensory nerves and therefore more sensitive to drug effects(2). A woman laboring with an epidural therefore misses out on the fetal ejection reflex, which helps her birth her baby quickly and easily, so she must use her own effort, often against gravity, to compensate this loss. This explains the increased length of the second stage of labor and the extra need for forceps when an epidural is used(3).
The use of epidurals also inhibits catecholamine release(4), which may be advantageous in the first stage of labor. Close to the time of birth, however, a reduction in CA levels will further inhibit the fetal ejection reflex, which involves catecholamines as well as oxytocin.
Release of the important uterine stimulating hormone prostaglandin F2 is also adversely affected by epidurals. The level of this hormone rises during an undisturbed labor; however, women with epidurals experience a decrease in PGF2 alpha and a prolongation of labor (5).
Drugs administered by epidural enter the mother’s bloodstream immediately and go straight to the baby at equal, or sometimes greater, levels(6,7). Some drugs will be preferentially taken up into the baby’s brain(8), and almost all will take longer to be eliminated from the baby’s immature system after the cord is cut. One researcher found bupivacaine and its breakdown products in the circulation of babies for the first three days(9).
Epidural anesthesia, used for cesareans, has also been associated with more acidemia (acid blood levels) in healthy newborn babies than has general anesthetic— an indication that epidurals can compromise fetal blood and oxygen supply(10) possibly through a drop in the mother’s blood pressure.
Mothers given epidurals in one study spent less time with their babies in the hospital, in inverse proportion to the dose of drugs they received and the length of the second stage of labor(11). In another study, mothers who had epidurals described their babies as more difficult to care for one month later(12). Such subtle shifts in relationship and reciprocity may reflect hormonal dysfunctions and/or drug toxicity and/or the less-than-optimal circumstances that often accompany epidural births—long labors, forceps and cesareans.
Sarah Buckley, Midwifery Today, Issue 63.
This article appeared in Pathways to Family Wellness magazine, Issue #05.
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