Final answer:
The discussion focuses on the importance of gestational age in determining the expected weight of a fetus, especially when an actual measurement is not available. It is highlighted that full-term pregnancy is considered to be 36-40 weeks with average birth weights between 2.7 and 4.6 kilograms, but many factors including IUGR and maternal health issues can affect birth weight.
Step-by-step explanation:
The question pertains to the gestational age over which the weight of a fetus is not known. In the context of human development, gestational age refers to the length of pregnancy from the first day of the woman's last menstrual period. Typically, a full-term pregnancy is around 36-40 weeks post-fertilization. Infants born before full term are considered preterm and are likely to have a lower birth weight. By the 38th week, the fetus is fully developed with weights usually ranging between 2.7 and 4.6 kilograms. However, if the weight is unknown, medical professionals rely on gestational age to assess development and the health status of the fetus and newborn.
Babies are expected to continuously gain weight until about 40 weeks of gestation. Besides prematurity, causes for suboptimal growth may include intrauterine growth restriction (IUGR), maternal health issues, and problems with the placenta. Right after birth, medical assessments like the Apgar score are utilized to determine the health of the newborn, and regular growth checks are recommended throughout infancy to ensure the baby is growing normally.