What is Preterm Birth and How is it Measured?

A pregnancy is now considered full term at 39 weeks. In the 1980s and 1990s, the increases observed in many high-income countries were attributed to the increase in the rates of multiple pregnancies and

preterm births

among people with assisted conception after treatment for subfertility. A preterm birth indicated to prevent fetal death is not an indicator of the baby's worsening health, even if it contributes to an increase in the rate of preterm births. In addition, as described in chapter 11, the outcomes of preterm infants are influenced by factors that lead to premature birth, organ immaturity, neonatal treatment, and the postnatal environment.Rarely is the more rigorous definition of small used for gestational age of a birth weight that is 2 or more standard deviations below the average.

Premature birth is one of the leading causes of death and a major cause of long-term loss of human potential among survivors around the world. The spacing between births, or the interval between pregnancies, is the time between a live birth and the beginning of the next pregnancy. However, provider-initiated preterm births will represent a relatively smaller proportion of all preterm births in these countries where access to diagnostic tools is limited.While birth weight is closely related to gestational age, it cannot be used interchangeably, since there is a normal birth weight range for a given gestational age and gender. Attention to the quality of data on causes of death could provide information on the mechanisms of preterm birth, as well as the causes of early fetal and neonatal deaths.

Therefore, many preterm babies are large for gestational age, but have a normal birth weight, and the mortality and morbidity rates of these babies differ from those of full-term babies with a normal birth weight. While birth certificates are intended to establish the date of birth, citizenship and nationality of a newborn, they contain valuable public health information and are the only national source of data on

birth weight

and

gestational age

.However, research on preterm birth would benefit from having more accurate population data on gestational age and from including information on how gestational age was estimated in national and research databases, including data from birth certificates. This includes developing and updating tools to improve the skills of health workers and evaluating the quality of care provided to mothers at risk of preterm birth and to premature babies. The probability of mortality and morbidity in an immediate preterm birth is compared to the risks of worsening intrauterine conditions (which could eventually cause fetal death) and, sometimes, of a worsening of the maternal condition.

The economic costs of preterm birth are high in terms of immediate neonatal intensive care and of complex, ongoing long-term health needs that are frequently experienced.Of the 1.2 million premature births estimated to occur in high-income regions, more than 0.5 million (42%) occur in the United States.