Even Moderately Premature Birth Poses Risk for Developmental Delays

Contrary to current assumptions, being born just two to four weeks premature can put a child at risk for minor delays in development, according to a study by researchers at the National Institute of Child Health and Human Development (NICHD) and the Health Resources and Services Administration. Although these delays, by themselves, are not likely to convey any long-term consequences for a child, pregnant women and their physicians should take them into consideration when deciding whether or not to induce labor early or perform an early C-section.

If inducing labor early is unavoidable, the researchers cautioned, physicians should counsel parents to have these children followed through early childhood to see if they will require any medical services to assist their development.

Publishing in the January issue of Pediatric and Perinatal Epidemiology, the researchers also reported that infants born even moderately undersize for their age are also likely to experience developmental delays.

Physicians commonly induce labor early in cases where the mother has a condition that threatens her health or the health of her unborn baby, and it is commonly thought that this practice carries few or no risks to a child's later development? said NICHD Director, Duane Alexander, M.D.?This finding suggests that women and their physicians should balance the risks of moderate prematurely against the risks of continuing the pregnancy before deciding whether to induce early labor?

Specifically, the researchers found that infants who were from 1 to 4 weeks premature-from the 33rd through the 36th week of pregnancy-were likely to experience a delay in one or two developmental milestones for a given age category, from birth through 47 months of age. Physicians consider a child to be full term when he or she is born in the 37th week of pregnancy or later.

The researchers also found that children who were smaller than normal for their age at birth were also likely to experience a delay in one developmental milestone in each age category.

Early induction of labor and, sometimes, cesarean section, are conducted for such complications as pregnancy-induced hypertension, gestational diabetes, and the life-threatening condition known as preeclampsia, explained the study's first author, Mary L. Hediger, Ph.D., a researcher with NICHD's Division of Epidemiology, Statistics and Prevention Research. In fact, she said, the number of infants born moderately preterm after induced labor has nearly doubled, from 9.1 percent in 1989 to 17.1 percent in 1996.

Dr. Hediger explained that the developmental delays the children experienced were very minor, such as failing to pick up small objects before 3 months of age, failing to crawl before six months of age, or failing to say two words other than mama? or dada? by 12 months. In all probability, the children will reach such developmental milestones when they are slightly older and not experience any long-term effects from the delay.

Inducing labor early is thought to be more acceptable than allowing the fetus to remain inside the womb when the mother's or fetal health is affected by a disorder of pregnancy? she said.

She added, however, that a cumulative effect may result when a child who faces other risks for developmental delays is born prematurely.

Being born to an older mother, being the youngest child in a large family, being born in poverty, being born to a family with a low educational level are all risk factors for developmental delays? Dr. Hediger said A combination of these risk factors, together with the developmental risks of moderate prematurity, might have a noticeable affect on development and might hinder a child's academic and other achievements?

Still, Dr. Hediger pointed out that in many cases inducing labor early might be absolutely necessary. For example, if ultrasound tests show that the fetus is failing to grow at a normal rate, the safest course for both mother and child may be to induce labor early.

It is possible, she said, that a condition complicating pregnancy, such as gestional diabetes or preeclampsia, may have an adverse effect on the fetus that causes these mild developmental delays.

We have no way of knowing whether or not these mild developmental delays might be worse if the pregnancy were not ended early. she said.

The main message, she added, is that physicians and caregivers should be on the alert for developmental lags in this group of children.

If a child is born moderately premature, caregivers should know that minor delays are likely and can check when the child is older to see if he or she needs any early childhood educational services.

Similarly, parents and physicians might wish to observe low birth weight infants to see if they reach their developmental milestones. Low birth weight is usually defined as less than 5 ½ lbs.

To conduct their research, Dr. Hediger and her coworkers reviewed information from the third National Health and Nutrition Examination Survey, conducted by the National Center for Health Statistics. In all, researchers examined the records of 4621 children born in single births, who were from 2 to 24 months of age when the survey was taken. The records included birth certificates and tests of children's motor and social development (MSD).

Records were available from children up to three months old, from four to six months, from seven to nine months, from ten to 12 months, from 13 to 15 months, from 16 to 18 months, from 19 to 21 months, and from 22 to 47 months.


The NICHD is part of the National Institutes of Health, the biomedical research arm of the Federal government. The Institute sponsors research on development before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. NICHD publications, as well as information about the Institute, are available from the NICHD website, http://www.nichd.nih.gov, or from the NICHD Information Resource Center, 1-800-370-2943; E-mail NICHDInformationResourceCenter@mail.nih.gov.

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