Having a baby is probably the most visceral time of a woman’s life. For nine months, we are buffeted by hormones that make us sick, tired, emotional, and occasionally forgetful. Our bellies swell; our breasts ache; we grow stretch marks and strange new patches of brown skin. Once the baby is born, it is usually placed, slippery and warm, on our chest, and a new tide of hormones overwhelms us, prompting our breasts to leak milk and sending us on another crashing roller coaster of emotional highs and lows. The aspect that I found hardest to deal with was the loss of control over my own body—and nowhere was this felt more acutely than in the timing of the actual event: birth.
For nine months, I diligently counted off the weeks, each one taking me a step closer to the day that had been circled heavily in my diary since my first doctor’s appointment: the due date. The two weeks before and all dates after were a no-man’s-land of uncertainty. Finally, I reached my due date, and hey presto, I was still pregnant. I felt like I was trapped in limbo—impatient and utterly powerless.
The trigger of birth remains one of the biggest mysteries of the human body. For years, people assumed that the baby came out when the mother’s uterus could stretch no farther and deflated like an overblown balloon, pushing the baby with it. A later view was that labor started when the mother was no longer able to supply enough oxygen and nutrients to sustain the baby’s growth, and the baby somehow triggered its own delivery. More recently, the focus has shifted, passing the reins of control to neither mother nor baby but to the gelatinous mass that has sustained the baby’s growth over nine months: the placenta.
Two hormones control the contractions that thin the cervix and expel the baby from the uterus: oxytocin and prostaglandin. It is these hormones that are given if labor has to be induced artificially or speeded up if it isn’t progressing fast enough. But what prompts a woman’s body to start producing these hormones in the first place?
This is a complex puzzle that scientists have spent years trying to unpick. Simplified, one of the current leading theories goes like this. Since shortly after conception, a tiny clock has been ticking in the cells that become the placenta, and it grows steadily louder and louder until those ticks can no longer be ignored. The physical manifestation of the clock is a hormone called CRH, which is produced by the placenta throughout pregnancy in larger and larger amounts until it reaches a critical threshold and unleashes a cascade of hormones that ultimately triggers birth.
First the baby’s brain releases two hormones, ACTH and DHEA, which prompt the placenta to start churning out large amounts of estrogen. This in turn initiates the production of prostaglandin and oxytocin, kick-starting the contractions of labor.
The idea of a placental clock is a nice one, but it doesn’t explain everything. For example, what causes the cervix to soften and prompts your water to break? One idea is that the immune system is involved. As the baby matures, its lungs begin to produce a substance called surfactant, which stops their moist linings from sticking together. But surfactant also gets out of the lungs and into the amniotic fluid, where it rallies immune cells to the uterus. These immune cells then release chemicals that soften the cervix and weaken the membranes containing the baby and amniotic fluid, making them more vulnerable to bursting. The fact that premature labor is often associated with infection lends support to the involvement of the immune system, as infection also activates the immune system.
Regardless of how it starts, it’s true to say that labor varies massively among women, as does their perception of the pain it causes. Some get stuck in the first stage of labor for days. Others whizz through and spend most of their labor in the second (pushing) stage. Still others are unable to give birth vaginally and require a C-section. Labor is nothing if not unpredictable. The best advice is to keep an open mind and be prepared for all possible scenarios.
My first child, Matilda, was due on August 31—the last day of the UK school calendar—which would have made her the youngest in her grade. Although plenty of geniuses have been born in August, there is some evidence that children who are the oldest in their school year are at an academic advantage, so I couldn’t help inwardly crossing my legs and hoping Matilda would hold on for an extra day (she was born a week overdue in the end, which is common for first babies; see 44: “Is it normal for pregnancies to run past their due date?”).
It’s widely assumed that women have no control over when they give birth, but a recent study has challenged this. Rebecca Levy and her colleagues at the Yale School of Public Health examined eleven years of U.S. birth records dating from 1996 to 2006, paying particular attention to the two-week periods surrounding Halloween and Valentine’s Day. Regardless of the type of delivery, women were 5 percent more likely to give birth on Valentine’s Day and 11.3 percent less likely to give birth on Halloween than in the two weeks surrounding these days.
As Halloween often carries negative connotations of death and evil, Levy suggests that women may subconsciously want to avoid having a baby on that day, while Valentine’s Day, with its associations of cute cherubs and love, may elicit the opposite reaction, although she hasn’t yet pinned down a biological mechanism by which positive or negative thoughts could trigger labor.
For centuries, the accepted wisdom has been that pregnancy lasts for nine calendar months and that you can calculate your due date by adding seven to the date of your last period, then counting back three months. This calculation became known as Naegele’s rule, after the nineteenth-century obstetrician Franz Naegele, who first published it in 1812.
It may seem ludicrous that a two-hundred-year-old calculation is still used to predict length of pregnancy. Indeed, many hospitals now use ultrasound to confirm the expected date of delivery based on a baby’s size at around twelve weeks of pregnancy, which is considered more accurate. Studies that have compared ultrasound dating to Naegele’s rule have found that, on average, Naegele’s date is three days too early.
However, this, too, is an average. First-time moms generally have longer pregnancies than women expecting their second, third, or fourth child. One study of Caucasian women found that although 61 percent of existing moms were overdue according to Naegele’s rule, they were only three days late on average (as ultrasound dating would predict). In contrast, the average first-time mom gave birth eight days later than Naegele would have predicted, and 81 percent were overdue.
Pregnancy length also varies according to racial background, with more South Asian and black women giving birth before thirty-nine weeks than white women. Their babies seem to be more developmentally advanced than those of white women born at the same stage.
All of this could have medical implications. Most obstetricians believe that remaining pregnant beyond forty-two weeks may put the mother’s and the baby’s health at risk, so they tend to induce labors that run seven to fourteen days past the expected due date. The main reason they give is the increased risk of stillbirth among babies born after forty-two weeks, which doubles from one per thousand pregnancies at forty-two weeks to two per thousand pregnancies at forty-three weeks. However, if the due dates are out, then women may be induced unnecessarily, which can carry risks of its own (see 47: “Will being induced mean I’m less likely to have a natural birth?”). In industrialized countries, rates of induction range between 10 and 25 percent of pregnancies, with around 22 percent of women in the U.S. being induced—although there is an ongoing debate about whether this number is too high.
Sex, curry, raspberry-leaf tea—there are a multitude of home remedies for kick-starting labor. By the time women reach the fortieth week of pregnancy, they’re usually desperate to meet their baby and will try anything to get the process moving. A friend of mine resorted to hours of frantic nipple-tweaking, which left her with very sore breasts, but she went into labor that night. Heavily pregnant myself, I tried imitating my friend but got nothing to show for it but a minor twinge. Pushing my skepticism aside, I paid a Chinese therapist thirty pounds for a massage, and eight hours later, my contractions started. An effective therapy, or was it simply that I was already seven days overdue and labor was destined to start anyway?
Fortunately, we don’t have to rely on anecdote to find out whether such home remedies really work, as a number of scientific studies have been done to evaluate them.
For centuries, herbalists have been using the leaves of the common red raspberry (Rubus idaeus) to prepare the uterus, and a recent survey of U.S.-based midwives found that 63 percent of them recommend it for inducing labor. However, in studies where raspberry-leaf extract has been given to animals or added to strips of uterine tissue, the results have been mixed: Some showed that it relaxed the muscle, others that it caused more coordinated contractions, while still others suggested that it increased the length of pregnancy.
Even if raspberry-leaf tea does affect the uterus, it’s not clear how much of the stuff you’d have to drink for the active ingredients to work their magic. One small study, which compared women who took raspberry-leaf tablets twice a day from thirty-two weeks with women who didn’t, found a very small reduction in the length of the second (pushing) stage of labor in the women who took the tablets, but the effect didn’t reach statistical significance, meaning that it could have been down to chance.
Disappointingly, there have been no studies to assess the value of curry in initiating labor (I would happily volunteer if there were). The theory is that the spice in curry irritates the bowels and triggers muscular contractions that send you rushing for the bathroom but may also spread to the womb and initiate labor.
Better studied is castor oil, which is thought to have a similar effect. Castor oil has been used to induce labor since ancient Egyptian times and was recommended by obstetricians in Western countries until the 1950s, when newer drugs such as Syntocinon (a synthetic form of oxytocin) became available. It is still used in many developing countries. Apparently, it’s pretty unpleasant to drink and may make you sick, as it has the taste and texture of very thick cooking oil. In 2012, an Israeli group announced the results of a prospective, randomized, double-blind, placebo-controlled study (which is about as good as it gets) on whether drinking castor oil induced labor: It found that the odds of entering labor within twelve hours of drinking castor oil were three times higher than if you drank sunflower oil. Women also seemed to progress through the first stage of labor more quickly. Unfortunately, there were just eighty women in the study, so more research is needed. Whether curry is an effective substitute, we don’t know, but it would probably have to be spicy enough to give you diarrhea—in which case you might prefer castor oil. The usual dose is four fluid ounces, which can be chased with orange juice, although it may be wise to speak to your doctor or midwife before trying it.
Pineapple contains an enzyme called bromelain, which could theoretically help to soften the cervix—although whether it would survive the harsh conditions of the digestive system and get into the blood in high enough amounts to have any effect seems unlikely. Tasty as it is, there is no scientific evidence to support the use of pineapple in inducing labor.
Tweaking, massaging, or pumping the breasts all spark the release of oxytocin, one of the hormones that causes labor contractions. A review of six trials involving a total of 719 heavily pregnant women found that more than a third of women who stimulated their breasts were in labor within seventy-two hours, compared to just 6 percent of those who didn’t. The amount of time the women spent tweaking their nipples or pumping their breasts varied from a total of one to three hours a day (with rests in between), and the women generally switched breasts every ten to fifteen minutes.
Although some doctors fear that nipple stimulation might overstimulate the uterus and potentially upset the baby, the review found no evidence of that (although its authors suggest avoiding nipple stimulation in high-risk pregnancies, just to be on the safe side). Nipple stimulation seemed to reduce the risk of excessive bleeding after birth, presumably because the extra oxytocin caused the woman’s uterus to contract more strongly and close off the blood vessels feeding the placenta after birth. A shot of oxytocin is often offered to birthing women in order to achieve the same effect.
Although sex may be the last thing on your mind when you’re about to give birth, many people will tell you that semen contains prostaglandins, which help to ripen the cervix. Possibly this rumor was started by men in a last-ditch effort to get some action before the baby arrives, but it seemed logical enough to warrant further investigation.
Swedish scientists recently asked twenty-eight heavily pregnant women either to have unprotected sex “with vaginal semen deposit” three nights in a row or to avoid sex completely. Because breast stimulation might have an independent effect, both groups were told that the nipples were absolute no-go areas. In this admittedly small study, sex didn’t seem to do anything. There was no difference between the women in terms of the baby’s position, the softness of the cervix, or the number of women who gave birth within the next three days. Having sex is unlikely to harm the baby, but it’s also unlikely to hasten its birth.
A handful of small trials have suggested that women receiving acupuncture are less likely to be medically induced, but because these women knew whether they were receiving genuine acupuncture, there may have been a placebo effect at work. Many other studies have found no effect.
The Cochrane Collaboration recently reviewed two trials of homeopathy in inducing labor. One found that women taking a mixture of black cohosh (Actea racemosa), arnica, caulophyllum, pulsatilla, and gelsemium twice a day from thirty-six weeks of pregnancy spent an average 5.1 hours in labor, compared to 8.5 hours for those who took a placebo pill, and suffered fewer complications—although the authors of the review said the study was too small to draw any firm conclusions. The second study looked at women whose water had broken prematurely and found that those taking an hourly dose of caulophyllum took an average thirteen hours to begin regular contractions, compared to 13.4 hours in women taking no supplements—a small enough difference for it to be down to chance.
If you sail past your due date, you might be offered something called a membrane sweep. It’s not the most dignified or comfortable procedure, involving a doctor or midwife sticking her fingers into your cervix and trying to stretch it and (if she can reach that far) separate the membranes containing the baby from the top of the cervix. This supposedly releases prostaglandins that further soften and thin the cervix, hastening the onset of labor.
Just how successful your doctor will be depends on the state of your cervix when she carries out the sweep. At forty to forty-one weeks, some women will have started to dilate, while others may be experiencing contractions even though their cervix shows little sign of softening, and the doctor may struggle even to reach it.
Plenty of studies have investigated whether membrane sweeping works, with mixed results. For this reason, the Cochrane Collaboration tried to review as many studies as it could in an attempt to draw some firm conclusions about the procedure. Generally speaking, membrane sweeping does increase your chances of going into labor within forty-eight hours or giving birth within the next week if you are already overdue—although it’s no guarantee. Eight women would need to have a membrane sweep in order for just one of them to avoid medical induction of labor, and it’s hard to know if you’d be in the lucky minority. Having a membrane sweep at thirty-eight to forty weeks of pregnancy also slightly reduces the chances that you’ll still be pregnant at forty weeks.
It’s a fairly unpleasant procedure and may trigger bleeding and painful contractions that don’t result in labor. In one of the studies reviewed, 70 percent of women reported significant discomfort, while a third reported significant pain. For this reason, the review’s authors say the rationale for membrane sweeping healthy women who aren’t overdue is questionable.
A woman sails through pregnancy healthy, happy, and excited about meeting her baby for the first time. As the due date passes, frustration and impatience can set in, but for women who remain stubbornly pregnant once they pass the forty-one-week barrier, a new terror awaits: the threat of induction.
Supporters of natural childbirth sometimes warn that being induced will make contractions more painful and difficult to cope with, which means that you’re more likely to need an epidural, which in turn can make a C-section or instrumental delivery (involving forceps or a ventouse) more likely. What’s more, because induction is a medical procedure, your baby’s heart rate will need to be monitored continuously, which makes it harder to move around during labor or use a birthing pool.
The evidence suggests that many of these fears are overblown (see 66: “Does an epidural make a C-section more likely?”). Medical induction is usually recommended once women reach forty-one or forty-two weeks, and several drugs can be used. The first strategy is usually to give prostaglandins to help soften the cervix and make it easier to open. If this doesn’t help, a plastic tube can be inserted into the back of the hand to provide a drip containing Syntocinon (an artificial version of the hormone oxytocin, which regulates contractions).
Some studies have indicated that women who are induced tend to request an epidural sooner than those entering labor naturally, which might suggest that the contractions are more difficult to cope with. It’s also possible that because induction is generally carried out in a hospital ward under a doctor’s supervision, women are simply more likely to be offered an epidural rather than being encouraged to use other methods of pain relief.
So what about the claim that being induced increases your risk of needing an emergency C-section? So widespread is this dogma that in 2009 the U.S. Agency for Healthcare Research and Quality (AHRQ), which produces guidance for doctors, decided to take a closer look. Although some studies have suggested that induction boosts the risk of having a C-section, they’ve tended to compare women who are induced to women who enter labor spontaneously. This might seem reasonable, except that most women who are induced are overdue, so it would be better to compare them with other overdue women who are simply waiting and monitoring the situation. These women may eventually enter labor spontaneously, or they may have to be induced—but watchful waiting can bring problems of its own, such as ending up with an excessively large baby who needs to be delivered by C-section anyway.
After reviewing seventy-six studies, the AHRQ found that women who were induced were 20 percent less likely to need a C-section than women who simply watched and waited. Their babies were also around 50 percent less likely to have meconium (poop) in their amniotic fluid, which is a sign of maturity and is more common in post-date babies but can increase the risk of breathing problems. Most of the studies analyzed looked at women at or beyond forty-one weeks of pregnancy. Before this, the risk of C-section appeared to be more or less equal in both groups of women. Two other large reviews published within the last ten years reached similar conclusions.
Women may fear that if being induced makes an epidural more likely, then it may boost the risk of an instrumental delivery (one involving forceps or a ventouse). A separate review of nineteen trials found a slightly increased risk of instrumental delivery among women who were thirty-seven to forty weeks pregnant when they were induced, but this disappeared when one looked at women who were forty-one to forty-two weeks pregnant. This is important because most women who worry about being induced will fall into the second category. Bear in mind that if your pregnancy is overdue and you aren’t induced, then your baby will keep on growing and may be harder to push out when the time does arrive. A similar picture emerges if one looks at women who are offered a Syntocinon drip, since their labor slows or stalls. Overall, it seems to shorten labor and ultimately make women less likely to need a C-section or instrumental delivery.
The message I take away is that although being induced may quash your dreams of a home or midwife-led birth, if you’re still pregnant two weeks past your due date, then it may be worth listening to the advice of your doctors. You can still hope for an otherwise uncomplicated natural vaginal delivery, and it may ultimately be safer for both you and the baby.
By the end of pregnancy, 90 percent of babies are head down and two-thirds of them are facing their mother’s spine, which is the optimum position for fitting through her pelvis. However, a stubborn few seem determined to face the other way around, which makes birth more painful, and a breech baby who remains head up will often need to be delivered by C-section.
Because the head is the heaviest part of the body, people may tell you to get down on your hands and knees and use gravity to turn a difficult baby. Unfortunately, there is little published evidence to suggest that this works. One recent review of three studies by the Cochrane Collaboration found that although getting on hands and knees for ten minutes a day caused a baby to rotate in the short term, it didn’t stay that way for long. Several other studies suggest that, although babies may shift position according to what the mother is doing at the time—aligning their bodies with the mother’s when she rests, for instance—they often revert to the original position or a different position afterward.
Women shouldn’t give up on the hands-and-knees position entirely, though: The Cochrane review found that it was effective at relieving back pain during labor.
Midwives may also try using something called external cephalic version (ECV) to turn a breech baby, which involves prodding and pushing at your bump in order to encourage the baby to flip a somersault. Success rates for this technique range from 35 to 57 percent for women in their first pregnancy, and from 52 to 84 percent for existing mothers, so it seems worth a try.
Relaxing in warm water is a great way of staving off early labor pains, but women are sometimes told that it is dangerous once water has broken because bacteria in the bathwater could be flushed into the uterus and infect the baby. This rumor seems related to a common distrust of water births, once considered dangerous because of fear of infection.
However, when Swiss researchers compared the risk of infection in mothers whose water had ruptured, they found no difference between those who took a warm bath and those who didn’t.
Several studies looked at infection rates in women who choose to have water births and found no increased risk of infection in either mother or baby. Despite water becoming contaminated with feces during a water birth, some obstetricians believe that it may even help to protect newborns against subsequent diseases and allergies (see 54: “Are vaginal births really better than C-sections?”).