Fetal Lungs Provide a Signal Initiating Labor

This isn't new information (the press release below was published in 2004), but it seems to be relatively unheard of among mothers and childbirth educators. It has significant implications and should greatly influence families' decisions about inducing labor or electing to deliver a baby via cesarean section. If the mother has not gone into labor, the baby most likely has not given the signal that he's ready!

A protein released from the lungs of a developing mouse fetus initiates a cascade of chemical events leading to the mother's initiation of labor, researchers at UT Southwestern Medical Center at Dallas have found.

The research, which has implications for humans, marks the first time a link between a specific fetal lung protein and labor has been identified, said Dr. Carole Mendelson, professor of biochemistry and obstetrics and gynecology and senior author of the study. The paper appears in an upcoming issue of the Proceedings of the National Academy of Sciences and is currently available online.

The initiation of term labor is carefully timed to begin only after the embryo is sufficiently mature to survive outside the womb. Previous studies suggested that the signal for labor in humans may arise from the fetus, but the nature of the signal and actual mechanism was unclear, Dr. Mendelson said.

In their study, UT Southwestern researchers found evidence that a substance secreted by the lungs of a developing fetus contains the key signal that initiates labor. The substance, called surfactant, is essential for normal breathing outside the womb.

"We found that a protein within lung surfactant serves as a hormone of labor that signals to the mother's uterus when the fetal lungs are sufficiently mature to withstand the critical transition to air breathing," Dr. Mendelson said.

"No one really understands what causes normal or preterm labor. There may be several chemical pathways that lead to labor, but we think that this surfactant protein, which is also produced by the fetal lung in humans, may be the first hormonal signal for labor," said Dr. Mendelson, who is co-director of the North Texas March of Dimes Birth Defects Center at UT Southwestern.

In humans the signaling protein, called surfactant protein A, or SP-A, also helps immune cells, called macrophages, fight off infections in the lungs of children and adults by gobbling up bacteria, viruses and fungi that infiltrate the lung airway.

"Women who go into preterm labor frequently have an infection of the membranes that surround the fetus, and the number of macrophages in the wall of the uterus increases with the initiation of preterm labor. When women go into labor at term, they also have an increase in macrophages in the uterus," Dr. Mendelson said.

This led the researchers to investigate whether there was a connection between what happens during normal labor at term and in infected mothers who go into early labor.

"This also raised the question: If bacterial infection can cause increased macrophage infiltration of the uterus in preterm labor, what is the signal for the enhanced macrophage migration to the uterus at term?" Dr. Mendelson said.

In mice, the developing fetal lung starts producing SP-A at 17 days gestation; full-term delivery occurs at 19 days. The developing human fetus starts producing SP-A in increasing amounts after 30 to 32 weeks of a 40-week normal gestation, at which time the baby's lungs are essentially developed. As the fetus "breathes" amniotic fluid in the womb, the protein is released into the fluid.

"The SP-A protein binds to macrophages in the amniotic fluid, macrophages that come from the fetus itself," said Dr. Jennifer Condon, a postdoctoral researcher in biochemistry and the study's lead author.

The macrophages, "activated" by the protein, make their way through the amniotic fluid to the wall of the uterus. Once embedded there, they produce a chemical that stimulates an inflammatory response in the uterus, ultimately leading to labor.

http://www.utsouthwestern.edu/utsw/cda/dept37389/files/158762.html

Cytotec Is Dangerous, No Matter What Your Doctor Told You...

There has been renewed conversation about Cytotec in my local doula community recently because a doula was concerned that this was what a doctor had prescribed for her client. A few doulas commented that their clients had experienced medically-induced labor with Cytotec and had good outcomes. But we must remember that a few happy endings are not evidence that the practice is safe.



This article by Marsden Wagner in a 2001 issue of Midwifery Today covers the major points...

Induction with Cytotec should never be attempted anywhere, most especially in out-of-hospital settings. Incredibly, the American College of Obstetricians and Gynecologists (ACOG) recently approved Cytotec induction: 1) in spite of lack of FDA approval; 2) in spite of a letter to doctors earlier this year from Searle (which manufactures Cytotec) imploring doctors not to use it for induction; 3) in spite of lack of approval from the Cochrane Library (the best scientific opinion); and 4) in spite of the fact that it is not approved nor used for induction in any country in Western Europe.

Recent articles in prestigious medical journals such as The Lancet have questioned the validity of standards of practice from professional organizations like ACOG, because their goal of protecting the health of women through using scientific evidence to guide members toward best practices too often conflicts with their other role as a trade union representing the interest of their members. As a result of this "trade union" role, ACOG recommendations are too often compromised by the needs of the obstetricians. A classic example of putting the doctors' needs ahead of the families' needs is the ACOG recommendation not to permit videotaping by families of a hospital birth.

So ACOG quotes studies of Cytotec induction, none of which have a sufficient number of research subjects, and consequently, none of the studies quoted have sufficient statistical power to detect small but potentially important risks such as uterine hyperstimulation and uterine rupture. Furthermore, because published studies of Cytotec induction have such wide methodological variability, meta-analysis is impossible and the published attempts at such meta-analysis are seriously flawed. But Cytotec is a godsend for busy obstetricians, as its use allows them to schedule the woman's labor at a convenient time and speeds up the labor, resulting in a return to "daylight obstetrics"-pharmacological induction of labor has increased from 10 percent to 20 percent in the past decade in the United States. So with their members' needs in mind, ACOG plows ahead, ignoring the best scientific evidence as well as the recommendations of the best scientific bodies, of government agencies not only in the United States but in every country in Western Europe, and of the pharmaceutical company. Instead, ACOG uses weak, inadequate evidence to approve Cytotec induction. Midwives should stay as far away as possible from such vigilante obstetrics-obstetricians taking matters into their own hands while ignoring the recommendations of the real judges.

article from Midwifery Today, Issue 57, Spring 2001, page 44

by Marsden Wagner MD, MSPH

Cover photo of Jessie and Hans © 2000 by Caroline E. Brown, DEd, MS, RNC.

http://www.midwiferytoday.com/articles/midwivescytotec.asp

Don't Short-Change Your Baby By Inducing Labor

I read this column on MSNBC today, about why women should not choose to induce labor in their final weeks of pregnancy. The author refers to a recent study that details the complications that come with late preterm births, including respiratory distress and difficulty sucking and swallowing.

I agree with the column, but I would add that the dangers of induction do not end at 40 weeks or the "due date" your doctor wrote in your medical file. Just because some babies are born around 40 weeks does not mean every baby is ready to be born at 40 weeks. Why induce at 40 weeks if you would not induce at 38?

Here are some good comments from Judith A. Lothian in the Journal of Perinatal Education:

Thinking of, and clinging to, the “due date” as “the day” makes it difficult for women to trust nature's beautiful plan for the end of pregnancy and the start of labor. What women rarely know, and what people tend to forget, is that some variation exists in how long it takes for an individual baby to mature fully. Acknowledging that babies can safely come 2 weeks before or 2 weeks after the due date does not tell the whole story. Some babies are mature as early as 37 weeks (259 days), and others need 42 completed weeks (294 days) and sometimes a bit more to be fully ready. Size is not an indication of maturity, and the due date is only a guideline.

She notes that "Waiting for labor to start spontaneously is almost always the best way to know that the baby is ready to be born and that a woman's body is ready for labor." Read her article for more details about the risks of induction: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1595289/