The nine months of pregnancy come complete with a rich folklore, from guessing at a baby’s sex by the expectant mother’s shape to home remedies for morning sickness. Along with these ageless stories and advice, women also face a variety of recommendations from the modern world of medicine on how best to take care of themselves during pregnancy. Yet new systematic reviews suggest that in some cases, the evidence supporting a link between prenatal care and specific outcomes may be as scarce as the data behind the “old wives’ tales.”.
Healthy Moms, Healthy Babies
Recently, physicians have shifted the focus of prenatal care further back into time, recommending healthy changes long before women consider having children. The success story of folic acid is part of this trend. In 1996, the Food and Drug Administration asked manufacturers to add folic acid to grain products like cereals and breads, and neural tube birth defects dropped by 19 percent in 2001 as a result. Exercise and diet counseling and domestic abuse screening are now part of the preconception care guidelines recommended by the U.S. Preventive Services Task Force and others.
New, Uncertain Technologies
Pregnancy has become less of a mystery in the past decade, with advanced ultrasound and similar techniques providing new ways to peek into the womb. But the costs and benefits of some of these new technologies remain uncertain. For instance, a 1999 review of fetal heart rate monitoring concluded that there was not enough evidence yet to know how the monitoring affected mother and child.
- A systematic review of studies of communication between pregnant women and their physicians suggests that women are less anxious about prenatal testing if the test information is provided in a variety of formats.
- About 2 percent of women, according to a 2001 Cochrane Collaboration systematic review of more than 2,500 patients, may prefer their pregnancy care to be led by a general practitioner or midwife as opposed to an obstetrician or gynecologist.
- A literature review of 296 studies found that abused pregnant women are more likely to have kidney infections, gain less weight and have cesarean deliveries.
- A 2005 meta-analysis concluded that progesterone drugs given to pregnant women at risk for premature deliveries could reduce rates of premature birth and low birth weight.
- Calcium supplements may reduce the risk of high blood pressure in pregnant women at high risk for gestational diabetes and those who have calcium-poor diets.
- Vitamin B6 may help prevent nausea and vomiting in early pregnancy, according to a 2003 Cochrane Collaboration systematic review.
- Group breastfeeding education classes can prolong the time that a mother nurses her children, according to a 2001 systematic review.
- The opinion of prominent physicians in a community can strongly influence rates of vaginal birth after cesarean section, a 2004 review found.
- Education programs to increase rates of vaginal birth after a previous cesarean section have no effect, according to a 2000 Cochrane Collaboration systematic review.
- The evidence that bed rest, special diets and birth education prevent low birth weight is inconclusive, according to a 2003 systematic review.
- The impact of gestational diabetes screening on the health of mothers and newborns is uncertain because there are no well-conducted, randomized controlled trials of such screening, according to the U.S. Preventive Services Task Force.
- A 2003 review found no suitable prenatal screening tests to predict postnatal depression in a general population of pregnant women.
Leaving Well Enough Alone:
In developed countries like the United States, pregnant women usually visit their obstetrician at least monthly over the course of a healthy and problem-free pregnancy. During these visits, women receive numerous blood and urine tests to detect high blood pressure, anemia, diabetes and birth defects in the fetus. At some stage in the pregnancy, women may undergo an ultrasound or some other form of fetal monitoring. At the very least, expectant mothers are handed a prescription for prenatal vitamins and a list of foods to eat and avoid.
The evidence that multiple visits, constant monitoring and special diets lead to better outcomes for baby and mother, however, is being questioned by new systematic reviews and large-scale analyses of available studies. For instance, a major review by the World Health Organization in 2001 found that women who visited their doctors only four times during their pregnancy were comparable to those who had 12 or more visits in rates of pre-eclampsia (a dangerous form of very high blood pressure among pregnant women), postpartum anemia, low birth weights and infant and mother deaths.
“ Traditionally, low-risk pregnant women in the United States who participate in prenatal care have been scheduled for about 14 to 16 prenatal visits, which is the schedule recommended by the American College of Obstetricians and Gynecologists,” says Deborah Walker, a clinical nursing professor at Wayne State University.
Walker says the available evidence from the WHO report and a similar study in 1989 by the U.S. Department of Health and Human Services16 suggests most women will do fine with fewer visits. But women who have been used to a certain level of care may have trouble getting used to that idea, according to the WHO report, which found that expectant mothers in developed countries like the United States were more dissatisfied with the reduced visit schedule.
Low birth weight and early delivery are among the most common pregnancy complications, and women at risk for those complications are treated with a variety of preventive measures. But according to Dr. Michael Lu of the University of California, Los Angeles School of Medicine, there is little evidence to support most of these treatments, including bed rest, childbirth education and antibiotic and hormonal treatments. Preterm births and low birth weights are not “effectively prevented by prenatal care in its present form,” Lu and colleagues concluded in a 2003 systematic review.
Among the other interventions offered routinely to pregnant women are ultrasound readings and nutritional advice. Yet there is scarce evidence to support either recommendation, according to recent reviews by the Cochrane Collaboration. In 2000, reviewers concluded that late term ultrasound in low-risk pregnancies does not benefit either mother or baby. A 2003 review found that there was no “consistent benefit” to mother or child when women ate more daily calories and grams of protein during their pregnancies.