A 2013 study found that "While only a small proportion of births occur before 24 completed weeks of gestation (about 1 per 1000), survival is rare and most of them are either fetal deaths or live births followed by a neonatal death." Postnatal use
Gestational age (as well as fertilization age) is sometimes used postnatally (after birth) to estimate various risk factors. For example, it is a better predictor than postnatal age for risk of intraventricular hemorrhage in premature babies treated with extracorporeal membrane oxygenation. Factors affecting pregnancy length
Childs gestational age at birth (pregnancy length) is associated with various likely causal maternal non-genetic factors: stress during pregnancy, age, parity, smoking, infection and inflammation, BMI. Also, preexisting maternal medical conditions with genetic component, e.g., diabetes mellitus type 1, systemic lupus erythematosus, anaemia. Parental ancestral background (race) also plays a role in pregnancy duration. Gestational age at birth is on average shortened by various pregnancy aspects: twin pregnancy, prelabor rupture of (fetal) membranes, pre-eclampsia, eclampsia, intrauterine growth restriction. The ratio between fetal growth rate and uterine size (reflecting uterine distension) is suspected to partially determine the pregnancy length. Heritability of pregnancy length
Family-based studies showed that gestational age at birth is partially (from 25% to 40%) determined by genetic factors. See also
Pregnancy
Maternity
Prenatal development
Gestation periods in mammals
Abortion law
Reproductive rights
Fetal rights


== References ==
On September 29, 2011, the FDA issued new guidance with regard to the DESI category. This effectively disallowed any new DESI formulations to enter the market. The FDA also has stated that DESI drugs do not have any therapeutic equivalent drugs listed in the “Orange Book”. In their description of therapeutic equivalence, the FDA specifically cites Donnatal®. Therefore, any so-called generic drugs on the market with similar formulation to DESI drugs, are considered illegal drugs as the FDA has not reviewed their composition or therapeutic equivalence. Donnatal, although containing phenobarbital, is exempt from the Controlled Substances Act due to the belladonna alkaloids present in the formulation. References
External links
"Donnatal Extended Release Tablet Information". Archived from the original on 2008-12-27.