In one sentence, describe what the following article is about:

The exact causes of hyperemesis gravidarum are unknown, although high levels of HCG (human chorionic gonadotropin) and estrogen may contribute to it. Women with multiple pregnancies (i.e. twins) are at a higher risk for hyperemesis gravidarum, as are women who are pregnant for the first time, and women pregnant with a female baby.  If hyperemesis gravidarum runs in your family (such as if your mother had it), or if you had it with a previous child, you may also be at a higher risk for developing it. Other risk factors include stress, anxiety, and depression. It's essential to see a healthcare provider regularly once you become pregnant. If you are trying to conceive, find an OB-GYN in your area so that you can schedule your first prenatal appointment as soon as you get pregnant. Make sure your OB-GYN accepts your health insurance. Women who are overweight may have a higher chance of developing hyperemesis gravidarum. Take up gentle exercise, like walking, swimming, or doing yoga, for 30 minutes per day 5 days per week. Speak to your healthcare provider before beginning an exercise regiment A vitamin B6 deficiency may increase your risk for hyperemesis gravidarum. Speak to your healthcare provider before taking any supplements. Vitamin B6 supplements may also decrease your chances of vomiting while pregnant.

Summary:
Understand the risk factors. Establish prenatal care. Lose weight if you are overweight. Take up to 40 mg of vitamin B6 per day.