Maternity leave, also known as parental leave or family leave, refers to the period of time that a mother takes off from work following the birth of her baby. The standards and practices surrounding maternity leave vary widely across the world, reflecting differences in cultural norms, economic structures, and government policies. This variance results in differing durations and conditions under which maternity leave is granted. Specific to the answers provided, "Answer A" suggests a duration of approximately 12 weeks while "Answer B" mentions a period of about 90 days. Although they sound different, these durations are nearly equivalent, with 12 weeks equating to roughly 84 days.

### Maternity Leave in the United States (Answer A: 12 weeks)
In the United States, maternity leave is primarily governed by the Family and Medical Leave Act (FMLA) of 1993. The FMLA entitles eligible employees of covered employers to take unpaid, job-protected leave for specified family and medical reasons, which include pregnancy and childbirth. Eligible employees can take up to 12 weeks of leave in a 12-month period for the birth and care of the newborn child. While the FMLA ensures job security, it does not require employers to provide paid leave; this aspect varies significantly between different employers and states. Some states and companies have indeed more generous provisions, including paid leave options, but 12 weeks remains the federal statutory standard.

### Maternity Leave in the European Context (Answer B: 90 days)
Many European countries have more generous maternity leave policies compared to the United States. For example, the standard maternity leave duration in countries like Italy is a mandatory period that often covers five months - two months before the expected due date and three months after childbirth. When expressed in days, this typically results in approximately 150 days of leave. However, the term "90 days" specifically is close to what is found in places like Russia or Brazil, where the leave is typically around 120 days, typically around four months. The term of 90 days, or approximately three months, can reflect the minimum standards observed in several countries, particularly when focusing solely on the post-birth period.

### Economic and Social Impacts of Maternity Leave
The duration and compensation during maternity leave can have significant economic and social implications. Studies suggest that longer maternity leaves can have positive impacts on maternal and child health, including increased rates of breastfeeding and improved child health outcomes. Economically, paid maternity leave can help maintain the labor force participation rate among women, while unpaid leave strategies might discourage return to work. Therefore, while designing maternity leave policies, governments weigh the benefits of maternal and child well-being against the economic implications of extended paid leave.

### Conclusion
Ultimately, the specific duration of maternity leave like those described in Answers A (12 weeks) and B (90 days) indicates the minimum standards set by legislation or typical practices within different jurisdictions. In the US, the three-month norm serves as a baseline largely because of FMLA, whereas the 90 days standard in other countries aligns with more generalized international practices aimed at ensuring the health and well-being of both the mother and the newborn. As global perspectives on parental leave evolve, it's possible these standards may also change, reflecting new research and shifts in societal values towards parenting and career balance.