Second trimester
Learning Center
Healthy sperm: Improving your fertility
You can take simple steps to have healthy sperm and improve your fertility.
Heart attack prevention: Should I avoid secondhand smoke?
It's possible that secondhand smoke can irritate the arteries and increase the risk of a heart attack.
Helping baby sleep through the night
Help your baby sleep through the night.
Hemolytic uremic syndrome (HUS)
Damage to the small blood vessels in the kidneys can cause clots that clog the organ's filtering system. This can lead to life-threatening kidney failure.
Herd immunity and COVID-19: What you need to know
To protect groups of people over time, it helps to know what level of recovery or vaccination in a population makes it hard for a germ to spread.
High-dose flu vaccines: How are they different from other flu vaccines?
High-dose flu vaccines are flu vaccines for older people.
Hip fracture
The risk of breaking a hip increases with age. Learn about lifestyle changes that can keep bones strong and reduce risk of breaking.
Hormone therapy for prostate cancer
Find out what to expect during testosterone-blocking therapy. Learn about choices, including medicines and surgery.
How do COVID-19 antibody tests differ from diagnostic tests?
Antibody testing shows whether you've had the COVID-19 virus in the past. It's not the same as testing to see whether you have the virus now.
How well do face masks protect against COVID-19?
Face masks can help slow the spread of coronavirus disease 2019 (COVID-19). Learn about mask types, which masks to use and how to use them.
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