Gases that contribute to the greenhouse effect include: 1  Water vapor. 2  Carbon dioxide (CO 2). 3  Methane. 4  Nitrous oxide. 5  Chlorofluorocarbons (CFCs).
You can start maternity leave any time from 11 weeks before the beginning of the week your baby's due. You can bring the date forward if you need to take time off work for pregnancy-related reasons within four weeks of the expected birth date. Your employer may make you start your leave from then.
Health benefits vs. work constraints. Not sure when to start your maternity leave? Although there is no magic number of weeks - or months - that is ideal, a new study says that taking some time before a baby's birth is ideal for both the mother-to-be and the infant.