Birth Weight

The modal weight group for babies born to New Jersey resident women in 1997 was 3,000 to 3,499 grams, which is approximately 6 lbs. 10 oz. to 7 lbs. 11 oz. Over one-third of births were in this weight category (35.5%) and an additional 28.1 percent of newborns weighed 3,500 to 3,999 grams (CHS, 2000a).

Low birth weight is defined as a weight at birth of less than 2,500 grams or approximately 5 lbs. 8 oz. There were 8,687 live births in this category in 1997. This was 131 more low birth weight infants born to New Jersey residents than in 1996. Low birth weight newborns accounted for 7.7 percent of live births in 1997, which is 2.7 percent higher than the 1996 percentage. Black mothers had a substantially higher percentage of low birth weight babies than did white mothers or other race mothers: 13.7 percent versus 6.3 percent and 8.0 percent, respectively (Table N7). The percentage of Hispanic mothers with low birth weight babies was slightly lower than the percentage for the newborns of all New Jersey mothers: 7.4 percent. Unmarried mothers had low birth weight babies 11.2 percent of the time, while for married mothers this percentage was 6.5 (CHS, 2000a).

Very low birth weight is defined as a weight at birth of less than 1,500 grams which is approximately 3 lbs. 5 oz.. In 1997, there were 1,816 births to New Jersey resident women in this weight category, accounting for 1.6 percent of total live births. This was an increase of 65 very low birth weight births from the 1996 number. Black mothers had a higher percentage of very low birth weight babies than did white or other race mothers: 3.6 percent versus 1.2 percent for each (Table N25). The percentage for Hispanic mothers was slightly lower than the state rate: 1.5 percent. There were 812 very low birth weight babies born to unmarried mothers in 1997, which is 2.6 percent of the total births to unmarried women, while married women had very low birth weight babies 1.3 percent of the time (CHS, 2000a).

Teenage mothers had a substantially higher percentage (10.1%) of low birth weight births than older women in 1997. White teen mothers had babies of low birth weight 7.8 percent of the time, while 12.7 percent of black teen mothers had low birth weight babies (Tables N7 and N11). Hispanic teens had a slightly lower percentage of low birth weight babies than non-Hispanic teens: 8.9 percent versus 10.7 percent, respectively (CHS, 2000a). Unmarried teenage mothers had a higher percentage of low birth weight births than married mothers of the same age: 10.7 percent versus 5.7 percent, respectively (CHS, 2000a). Birth weight by age and race of the mother is provided in Table N25. Birth weight by mother's county and selected municipality of residence is presented in Table N26.

In addition to age, race, and marital status, low birth weight is associated with the number of previous pregnancy terminations (fetal deaths, either spontaneous or induced) experienced by the mother. While mothers with no prior pregnancy terminations had low birth weight rates below that of the entire population (7.0% vs. 7.7%), mothers with one previous termination had low birth weight babies 7.7 percent of the time. With two previous terminations the low birth weight percentage rose to 9.6 and mothers with three or more prior terminations had a low birth weight rate of 13.4 percent (Figure N4 and Table N27).

Low birth weight is also associated with onset of prenatal care. Of mothers who began prenatal care in the first trimester of their pregnancy, 6.9 percent had low birth weight babies. For mothers who began prenatal care in the second or third trimester, low birth weight outcomes occurred in 8.2 percent and 7.8 percent of cases, respectively. Among mothers who obtained no prenatal care, 29.9 percent had babies weighing less than 2,500 grams (Figure N5 and Table N28). Table N29 provides details on birth weight by onset of prenatal care by race of the mother.

Apgar Score

The Apgar score is a composite measure used for the clinical evaluation of an infant one minute and five minutes after birth. A score of zero, one, or two is assigned in each of the following areas: heart rate, respiratory effort, color, muscle tone, and reflex irritability. Assigned values for the five areas are summed and a score of zero to ten results. An overall score of ten is optimal. An Apgar score under seven is considered indicative of potential health problems.

In this report, analysis of findings based on the Apgar score is limited to the five-minute results. A perfect score of ten was recorded on 8.4 percent of resident birth certificates in 1997. Scores of seven through nine were reported on 86.0 percent of certificates. Only 1.0 percent scored less than seven. On 4.6 percent of birth certificates, the five-minute Apgar score was not stated.

By race, the percentages of black, white, and other race births scoring zero through six on the five-minute Apgar score were 2.1, 0.7, and 0.8, respectively. For scores of seven through ten, the percentages were 96.3, 96.5, and 98.1 for blacks, whites, and other races, respectively. The five-minute Apgar score was not stated on 1.6 percent of black, 2.8 percent of white, and 1.1 percent of other race birth certificates in 1997 (Table N30).

Teenage mothers had a higher percentage of low (under 7) five-minute Apgar scores (1.5%) than did mothers over the age of twenty (0.9%) (Table N31). However, the percentage of unstated scores increases with age of the mother, so these findings are not conclusive. These missing data are most likely the result of this item not being provided in the information received on deliveries of babies of New Jersey residents which occurred in other states, mostly New York and Pennsylvania.

While babies of mothers who received prenatal care in the first trimester had five-minute Apgar scores of zero to six only 0.9 percent of the time, 5.9 percent of mothers who received no prenatal care had scores this low (Table N32). It should be noted that 4.6 percent of birth certificates had no information recorded for Apgar score and 7.6 percent had no data on onset of prenatal care, therefore results are inconclusive.

Abnormal Conditions of Newborns

Since the revision of the New Jersey certificate of birth in 1989, information on abnormal conditions of newborns has been available. The most frequently reported abnormal condition of newborns in New Jersey in 1997 was assisted ventilation of 30 minutes or more at a rate of 7.7 per 1,000 live births (Table N33). By race, the rates of assisted ventilation greater than or equal to 30 minutes were 12.5 for blacks, 7.0 for whites, and 6.1 for other races. The second most frequently reported condition was hyaline membrane disease/respiratory distress syndrome (RDS) at a rate of 4.6 per 1,000 live births. For hyaline membrane disease/RDS, the rates by race were 8.1 for blacks, 3.8 for whites, and 5.1 for other races. Increases in rates of abnormal conditions of newborns over previous years may be attributable to more complete reporting since the implementation of the Electronic Birth Certificate.

Congenital Anomalies

Congenital anomalies are the leading cause of infant death in New Jersey and in the U.S. Since 1989, information about congenital anomalies has been available on the birth certificate in the form of a checkbox item. This replaced the previous open-ended question in an effort to improve uniformity and completeness of reporting.

Among New Jersey residents in 1997, the congenital anomaly most frequently reported on the certificate of birth was musculoskeletal/integumental anomalies (4.7 per 1,000 live births). This includes cleft lip/palate, polydactyly/syndactyly/adactyly, club foot, and diaphragmatic hernia (included in other musculoskeletal/integumental anomaly). The second most frequently reported anomaly was circulatory and respiratory anomalies (2.5 per 1,000 live births), which includes heart malformations. By race, the rates of musculoskeletal/integumental anomalies per 1,000 live births were 7.3 for blacks, 4.1 for whites, and 5.2 for other races. For circulatory/respiratory anomalies, the rates per 1,000 live births by race were 2.4 for blacks, 2.6 for whites, and 2.9 for other races (Table N34).

New Jersey maintains a separate, population-based Birth Defects Registry within DHSS. Children diagnosed with a congenital defect by age one are required to be reported to the State. A wide range of medical practitioners must complete the confidential registration forms which are submitted to Special Child Health Services. Up to eight diagnoses are reported for each child, which provides a detailed medical description of the child. As new information on a child becomes available, the Registry updates its database to reflect the new diagnoses. As such, the data in the Registry may reflect more accurately than the birth certificate data the population of newborns and children with congenital anomalies in New Jersey. (P. Costa, personal communication, July 27, 1995).

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