NEW JERSEY HEALTH STATISTICS, 2003

            INFANT AND FETAL MORTALITY

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OVERVIEW

In 2003, there were 662 infant deaths and 756 fetal deaths among New Jersey residents. Of the infant deaths, 476 were in the neonatal period. Perinatal mortality is defined as fetal plus neonatal deaths, so there were 1,232 perinatal deaths.

Between 1993 and 2003, the infant mortality rate in New Jersey decreased by one-third, from 8.4 to 5.7 deaths per 1,000 births. The neonatal mortality rate decreased 29% to 4.1 and the postneonatal rate decreased 41% to 1.6 deaths per 1,000 births. A similar decline did not occur with fetal mortality, and by 1997 the fetal mortality rate exceeded the infant mortality rate. In 2003, the fetal mortality rate was 6.4 per 1,000 births plus fetal deaths of 20 or more weeks gestation. The perinatal mortality rate decreased 14% from 1993 to 2003 and was 10.5 per 1,000 births plus fetal deaths in 2003 (Table IF1 and Figures IF1 - IF3).

Among the 14 counties with enough infant deaths in 2003 to calculate a reliable rate, rates ranged from 3.0 in Monmouth County to 11.6 in Cumberland County. Fetal mortality rates ranged from 4.4 in Morris County to 11.1 in Essex County among counties with reliable rates. Of the 16 counties with reliable perinatal mortality rates, rates ranged from 6.7 in Somerset County to 16.7 in Essex County (Table IF2).

Of the 1,418 infant and fetal deaths in 2003, 1,232 (87%) occurred in the perinatal period between 20 weeks gestation and 27 days of life. It is useful to examine perinatal mortality factors to gain more information than what is available from infant death or fetal death statistics alone. The Black perinatal mortality rate (21.4) was twice that of the population as a whole. The rate among Hispanics (10.5) was equal to the overall rate, while rates among Whites (7.4) and Asians/Pacific Islanders (8.4) were slightly lower. Perinatal mortality rates were highest among the youngest (12.9) and the oldest (12.6) mothers. Women aged 30-34 years experienced the lowest perinatal mortality rate (8.6) in 2003. The pattern was the same for Whites, but not for Blacks or Hispanics. Among Blacks, the highest rates were among those aged 35-39 years (26.4) and 25-29 years (23.0) and the lowest rate (18.0) was among those aged 20-24 years. Among Hispanics, those aged 35-39 (13.0) and 30-34 (11.5) years had the highest rates and those aged 25-29 years had the lowest rate (9.0). Low numbers of perinatal deaths among Asians/Pacific Islanders hinders analysis by age and other characteristics (Table IF3).

The perinatal mortality rate among unmarried mothers (15.1) was nearly double the rate among married mothers (8.3). The marriage effect was most pronounced among Whites (10.9 vs. 6.7) and least marked among Hispanics (11.2 vs. 9.7). Multiples (twins, triplets, etc.) were four times more likely to die in the perinatal period than singletons (36.7 deaths per 1,000 vs. 9.0). The affect of plurality was more extreme among Hispanics and Whites and less evident among Blacks. While there were slight differences based on trimester of prenatal care onset, complete lack of prenatal care had a substantial affect on perinatal mortality.  The perinatal mortality rate among those who received prenatal care was 9.0 while the rate among those who did not receive care was 64.4, a difference of over 700%. Rates were higher for mothers who smoked during pregnancy (15.7) than among those who did not (10.0) (Table IF3).

The most influential factor in perinatal mortality was length of gestation. More than half of those delivered prior to 28 weeks gestation died in the perinatal period (569.6 per 1,000). Between 28 and 31 weeks gestation, the rate decreased dramatically to 75.8. At 32-36 weeks gestation, the rate declined further to 17.4 and was 1.9 for those delivered full-term (after 36 weeks gestation). Similar patterns were exhibited among all races/ethnicities. Birth/delivery weight is closely tied to gestational length.  Over one-third of those weighing less than 1,500 grams at delivery died in the perinatal period (349.0 per 1,000).  The rate was 19.7 for those weighing 1,500-2,499 grams and 1.8 for those weighing 2,500 grams or more. The pattern was the same for all races/ethnicities (Table IF3).

The leading causes of perinatal mortality in 2003 were fetal death of unspecified cause (211 deaths); placenta, cord, and membrane complications (210); short gestation and low birth weight (192); maternal complications of pregnancy (184); and congenital anomalies (137). Combined, these five causes accounted for more than three-quarters of perinatal deaths. No cause of death was given on 86 records (7%), so it is likely that even more deaths were attributable to those five causes (Table IF4).

INFANT MORTALITY
Race/ethnicity of mother

Infant mortality rates decreased among all races/ethnicities between 1993 and 2003, yet the rate among Black mothers remained more than twice the rate for any other race/ethnicity. In 2003, there were 12.0 infant deaths per 1,000 births to Black women. The rates were 3.5 for Whites, 5.2 for Hispanics, and 4.8 for Asians/Pacific Islanders (Table I1 and Figure I1). Thirty-five percent of Black infant deaths were in the postneonatal period compared to 26% for Whites, 25% for Hispanics, and 21% for Asians/Pacific Islanders (Table I10).

Age of mother

Infant mortality rates decreased among all age groups between 1993 and 2003. Infant mortality rates were negatively correlated with age except for the oldest mothers. Rates in 2003 declined from a high of 9.2 for mothers under 20 years old to a low of 3.6 for those aged 35-39 years, before rising to 6.6 for mothers aged 40-44 years. (Table I2 and Figure I2).

While infant mortality rates declined with increasing age up though 39 for other races/ethnicities, the same was not true for Black mothers. Rates increased from ages 20 to 34 with the highest rate (14.3) occurring among mothers aged 30-34 (Table I10).

Marital status

Although rates decreased more for unmarried mothers between 1993 and 2003, the infant mortality rate among unmarried mothers was still more than double the rate among married mothers in 2003. The rate was 3.9 per 1,000 births among married mothers and 8.8 among unmarried mothers (Table I3 and Figure I3). The difference between married and unmarried mothers was less marked among Blacks and Hispanics. Rates among unmarried Black and Hispanic mothers were 1.4 and 1.3 times higher, respectively, than for their married counterparts (Table I10). 

Multiple births

The infant mortality rate among singletons decreased 40% between 1993 and 2003 and stood at 4.4 per 1,000 births in 2003. The rate among multiples decreased 30% and was 25.9 in 2003. The infant mortality rate among multiple births was nearly six times as high as that among singletons (Table I4 and Figure I4). The difference was more extreme among Whites (8 times higher) and Hispanics (10 times higher) and less extreme among Blacks (3 times higher) (Table I10).

Prenatal care

The infant mortality rate among women who received no prenatal care was six times higher than the rate among those who did receive care. In 2003, rates were 4.7 for first trimester prenatal care onset, 5.5 for second and third trimester, and 30.9 for no prenatal care. Between 1993 and 2003, there was a 44% decrease in the infant mortality rate among mothers who received no prenatal care. Less dramatic decreases occurred for first, second, and third trimester prenatal care onset (Table I5 and Figure I5).

Tobacco use during pregnancy

The infant mortality rate was higher among mothers who reported smoking. While there was only a slight difference in infant mortality rates for White smokers and non-smokers, Black mothers who smoked were twice as likely to experience an infant death (Table I10). Similar declines in infant mortality rates from 1993 to 2003 were seen among mothers who did and did not use tobacco during pregnancy. The rate remained higher among smokers (8.3 deaths per 1,000 births) than among non-smokers (5.1) in 2003 (Table I6 and Figure I6). 

Period of gestation

Length of gestation was negatively related to the infant mortality rate. While only 1.4 out of every 1,000 full-term births died within the first year of life, the rate was 8.4 for those born between 32 and 36 weeks gestation. For those born prior to 32 weeks gestation, the infant mortality rate was 195.2 per 1,000 births or nearly 20% of those births (Table I7 and Figure I7). Prematurity had a slightly greater effect on infant mortality among Whites and a lesser effect among Blacks as compared to the population as a whole (Table I10). While infant mortality rates decreased by one-quarter among those delivered preterm (prior to 37 weeks gestation), rates among full-term deliveries decreased by more than half (Table I7 and Figure I7).

Birth weight

Birth weight and length of gestation are closely related. While mortality rates decreased about 30% among infants of low birth weight (less than 2,500 grams), rates among normal weight infants decreased by more than half. While only 1.3 out of every 1,000 normal weight births died within the first year of life, the rate was 10.6 for those weighing between 1,500 and 2,499 grams. For those of very low birth weight (less than 1,500 grams), the infant mortality rate was 212.1 per 1,000 births, or more than one-fifth of those births (Table I8 and Figure I8). Very low birth weight had a greater effect on infant mortality among Whites and Hispanics and a lesser effect among Blacks as compared to the population as a whole (Table I10).

Sex

Infant mortality rates for males remained slightly higher than rates for females throughout the period from 1993 to 2003. In 2003, the infant mortality rate was 6.0 for males and 5.3 for females (Table I9 and Figure I9).

Medical risk factors

The most commonly reported medical risk factors on birth certificates of infant deaths in 2003 were diabetes (29 deaths), acute or chronic lung disease (28), hydramnios/oligohydramnios (25), incompetent cervix (24), and previous preterm or small-for-gestational-age infant (23). Of those, the highest infant mortality rate was associated with incompetent cervix (39.3 deaths per 1,000 births) which is characterized by painless dilation of the cervix in the second trimester or early in the third trimester of pregnancy, with premature expulsion of membranes through the cervix and ballooning of the membranes into the vagina, followed by rupture of the membranes and subsequent expulsion of the fetus (Table I11 and Figure I10).

Causes of death

Short gestation/low birth weight and congenital anomalies have been the two leading causes of infant death since at least 1999. In 2003, 40% of infant deaths were attributed to those two causes. SIDS and respiratory distress have been the third and fourth leading causes since 1999. In 2003, the fifth leading cause was a tie between maternal complications of pregnancy and bacterial sepsis (Table I12 and Figures I11 and I12).

The leading causes of neonatal mortality in 2003 were short gestation/low birth weight (159 deaths) and congenital anomalies (78). SIDS (32 deaths) and congenital anomalies (27) were the leading causes of postneonatal deaths (Table I13).

The two leading causes of infant death were the same for all races/ethnicities in 2003: short gestation/low birth weight and congenital anomalies. For Whites, the third leading cause was a tie between SIDS and maternal complications of pregnancy. For Blacks, it was SIDS. For Hispanics, there was a three-way tie between SIDS, respiratory distress, and kidney disorders. For Asians and Pacific Islanders, the third leading cause of infant death was a tie between respiratory distress and maternal complications of pregnancy (Table I14).

FETAL MORTALITY
Race/ethnicity of mother

Fetal mortality rates decreased substantially among Hispanics and Asians/Pacific Islanders between 1993 and 2003, but remained virtually unchanged for Whites and increased among Blacks. Like infant mortality rates, the fetal mortality rate among Black mothers was more than twice the rate for any other race/ethnicity. In 2003, there were 13.8 fetal deaths per 1,000 births to Black women. The rates were 4.6 for Asians/Pacific Islanders, 4.8 for Whites, and 6.7 for Hispanics (Table F1 and Figure F1).

Age of mother

Fetal mortality rates were lowest for mothers aged 30-34 years (5.1 deaths per 1,000 births plus fetal deaths in 2003) and highest among mothers aged 40-44 years (7.9). There were no clear upward or downward fetal mortality rate trends among any age group between 1993 and 2003 (Table F2 and Figure F2).

Marital status

In 2003, the fetal mortality rate among unmarried mothers was 1.7 times higher than the rate among married mothers. The rate was 5.3 per 1,000 births plus fetal deaths among married mothers and 9.2 among unmarried mothers (Table F3 and Figure F3). As with infant mortality, the difference between married and unmarried mothers was less marked among Blacks and Hispanics. Rates among unmarried Black and Hispanic mothers were only 1.1 and 1.05 times higher, respectively, than for their married counterparts (Table F10).

Multiple births

There was no strong trend in fetal mortality rates among singletons or multiples between 1993 and 2003. The fetal mortality rate was 5.9 per 1,000 births plus fetal deaths for singletons and 17.0 for multiples in 2003. The rate for multiples was nearly three times higher than the rate among singletons (Table F4 and Figure F4) while the difference in plurality-specific rates was six-fold for infant deaths (Table I4 and Figure I4).

Prenatal care

The fetal mortality rate in 2003 among women who received no prenatal care was more than seven times higher than the rate among those who did receive care. Rates were 5.6 for first trimester prenatal care onset, 6.1 for second trimester, and 42.2 for no prenatal care. There was also no clear trend in fetal mortality rates by trimester of prenatal care onset between 1993 and 2003 (Table F5 and Figure F5).

Tobacco use during pregnancy

Since 2000 there has been a steady upward trend in fetal mortality rates among mothers who used tobacco during pregnancy.  The rate was 10.3 deaths per 1,000 births plus fetal deaths among smokers and 6.3 among non-smokers in 2003 (Table F6 and Figure F6).

Period of gestation

In 2003, the fetal mortality rate was 336.5 deaths per 1,000 births plus fetal deaths delivered between 20 and 27 weeks gestation, 58.9 for 28-31 weeks, 13.5 for 32-36 weeks, and 1.3 for 37 or more weeks gestation (Table F7 and Figure F7). While fetal deaths of 20-27 weeks gestation comprise about half of White, Hispanic, and Asian/Pacific Islander fetal deaths, they comprise two-thirds of Black fetal deaths (Table F10). While there was no clear fetal mortality rate trend among those delivered after 27 weeks of gestation, there was a steady climb during 1993-2002 among those delivered between 20 and 27 weeks. The rate decreased in 2003 for that group; however it still remained far higher than that of those delivered after 27 weeks gestation (Table F7 and Figure F7).

Delivery weight

While there was no clear fetal mortality rate trend among those weighing 1,500 grams or more at delivery, there was a fairly steady increase in the rate between 1993 and 2002 among those weighing less than 1,500 grams. The fetal mortality rate was 1.3 among those weighing 2,500 grams or more and 13.9 for those weighing between 1,500 and 2,499 grams. For those of very low delivery weight (less than 1,500 grams), the fetal mortality rate was 206.1 per 1,000 births plus fetal deaths (Table F8 and Figure F8). The proportion of fetal deaths which were of normal delivery weight varied by maternal race/ethnicity. While 10% of Black fetal deaths were of normal delivery weight, 25% of Hispanic, 21% of White, and 17% of Asian/Pacific Islander fetal deaths were (Table F10)

Sex

Like infant mortality rates, fetal mortality rates for males remained slightly higher than rates for females throughout the period from 1993 to 2003. In 2003, the fetal mortality rate was 6.6 for males and 6.1 for females (Table F9 and Figure F9).

Medical risk factors

The most commonly reported medical risk factors on fetal death certificates in 2003 were incompetent cervix (45 deaths), pregnancy-associated hypertension (31), previous preterm or small-for-gestational-age infant (28), diabetes (27), sexually transmitted diseases (27), and chronic hypertension (23). Of those, the highest fetal mortality rate was associated with incompetent cervix (68.7 deaths per 1,000 births plus fetal deaths) (Table F11 and Figure F10).

Causes of death

Fetal death of unspecified cause was the leading cause of fetal death in 2002 and 2003. Prior to 2002, placenta, cord, and membrane complications was the leading cause of fetal death. It was number two in 2003 and maternal complications of pregnancy was third. In 2003, 74% of fetal deaths were attributed to those three causes. Congenital anomalies has been the fourth leading cause since 1999.  In 2003, the fifth leading cause was maternal complications that may be unrelated to this pregnancy (Table F12 and Figures F11 and F12).

The three leading causes of fetal death were the same for all races/ethnicities in 2003: fetal death of unspecified cause; placenta, cord, and membrane complications; and maternal complications of pregnancy. However, the ranking of those three varied slightly by race/ethnicity. For Whites, the leading cause was placenta, cord, and membrane complications. For Asians and Pacific Islanders, the leading cause of fetal death was a tie between placenta, cord, and membrane complications and maternal complications of pregnancy (Table F13).

The Technical Notes section contains detailed information on sources of data, allocation of data by residence or occurrence, quality of data, racial and ethnic classification, definitions, and rates and ratios.

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