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.
You can decide how you would like to take the remaining weeks. Generally, employees take 2 weeks before the birth and the remaining weeks after. If you qualify for Maternity Benefit (see below) at least 2 and no more than 16 weeks must be taken before the end of the week the baby is due.