Giving birth

Childbirth fast forward

The average length of pregnancy is dropping largely due to induction and Caesarian section

By Sheila Kitzinger
Childbirth fast forward


For thousands of years, the average length of human pregnancy has been 40 weeks. Now, in a single decade, that has changed; in the US, it has dropped to 39 weeks. The change is largely due to higher rates of medical intervention, including earlier induction and Caesarean section. We asked renowned British childbirth expert and social anthropologist Sheila Kitzinger to comment on this trend.

Why is pregnancy being cut short?

Why is pregnancy being cut short like this? Labours are induced and elective Caesareans performed to cut pregnancy short, in the belief that babies are safer out than in once there are only a few more weeks of pregnancy to go, and that mothers — and obstetricians — want to plan ahead. Labour takes hours, sometimes days. So scheduling surgery seems to be an efficient, cost-effective way of managing birth that is otherwise unpredictable. There are other reasons too: the growing epidemic of obesity, for example. But they are trivial beside the human interventions in obstetrics that dictate the date and time of birth.

Perhaps 39 weeks doesn’t sound all that different. But there are hidden risks, which are only just now being discovered. Between 1992 and 2002, the percentage of full-term births declined by more than 20 percent, while “late preterm births” (between 34 and 36 weeks) went up by 12 percent. Nancy Green, associate professor of paediatrics and obstetrics at Albert Einstein College of Medicine in New York and medical director of the March of Dimes, sees this as “a growing concern.”

“While babies born late preterm often are considered healthy, they have higher risks of complications at birth than babies born just a few weeks later at full term,” says Green. In an article published in the National Post, she goes on to say, “They have a greater likelihood of breathing problems like respiratory distress syndrome (RDS), feeding difficulties, temperature instability (hypothermia), jaundice and reduced brain development than full-term babies.” Mothers of late preterm babies are more likely to confront breastfeeding problems because these babies are not quite neurologically ready for the major adaptation to life outside the uterus.

Obstetricians are often completely unaware that some of these babies have problems. Dr. David Savitz, an epidemiologist at Mount Sinai Medical Center, New York, who studies trends in preterm births says, “When you look at large populations, there are small but very real increases in the risk of adverse outcomes for those 34-, 35- or 36-week babies, but it may be something that an individual clinician never sees. If there is a major problem being prevented, then early delivery is absolutely justified. But it is important for both the clinician and the patient to be aware that this risk exists.”

Occasionally, in spite of ultrasound (which can give a date two weeks either way), the experts get it wrong and a baby who is thought to be 36 or 38 weeks turns out to be 32 or 34 weeks, and needs to be sent to the intensive care nursery for help with breathing and nasogastric feeding.

A baby can plump up by half a pound a week at the end of pregnancy, and this additional growth prepares it for the challenges of life. That extra time being rocked in the cradle of the mother’s pelvis as she moves, hearing the steady drumming of her heartbeat, and being nourished directly from her bloodstream as it is filtered through the placenta — this, too, may help a baby mature.

Even when the baby is ready to be born, induction of labour changes the physiology of birth and is not risk-free. When birth is kick-started, the mother may need strong painkilling drugs because huge contractions come in quick succession; she feels as if she is helpless and drowning in a storm at sea.

If she has an epidural, the most effective analgesic available, the baby’s heart rate may drop and then other drugs are used to stimulate it. Both mother and baby may develop a fever — a common side effect of epidurals — so after birth they go through a series of tests for infection.

An epidural makes labour longer, especially the pushing stage. If the mother has no spontaneous desire to push, she finds it difficult to work with her body to get the baby out and, because the epidural has caused loss of tone in her pelvic-floor muscles, the baby’s head may not rotate to get in the best position for birth. All this increases the chance of an instrumental delivery using forceps or vacuum extraction, or an emergency Caesarean section. A high proportion of planned early deliveries — which are close to 30 percent of all births in the US — are either elective Caesareans or failed inductions that end up as emergency C-sections.

Induction of labour and the Caesarean section that often results leave many women distressed in the months after birth. At first they feel relieved that they have got through the ordeal and the baby has arrived. Then, after some weeks or months, it hits them. They feel they were denied any control over the way the baby came into the world and were just a body on the delivery table. Some feel as if they have been violated. But they are supposed to be grateful to the medical system that did this to them. People tell them they should be happy they have a healthy baby, to put it behind them and get on with their lives. But intense memories of the birth go round and round in their heads like a videotape loop that cannot be switched off. They suffer nightmares, flashbacks and panic attacks. This is post-traumatic stress disorder. Their unhappiness is likely to affect how they feel about the baby, themselves as women, and their partners.

In the UK and other European countries, a long-term study is taking place to discover whether, when babies are diagnosed as not growing well in utero, it is best to leave labour to start spontaneously or to deliver the baby. The children are being followed until they are nine years old to find out if intervention to shorten pregnancy has any effect on physical development, intelligence, learning ability, language and behaviour. But research like this takes time and, meanwhile, there are increasing numbers of late preterm births.

Childbirth is not only a matter of having a live baby and a live mother. The way it is conducted, the setting where it takes place, and every intervention, even if routine, even if necessary, needs to be examined and evaluated in terms of the effect it has on the baby and the mother, sometimes for months or years later.

This article was originally published on Dec 01, 2006

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