For many women, the first day of their period can feel overwhelming. There is lower abdominal pain, heaviness, backache, and sometimes even nausea or loose motions.
Simple daily tasks can suddenly feel difficult. But by the third or fourth day, the pain usually becomes milder and more manageable.
So why does this happen?
According to Dr Keerti Khetan, Director, Department of Obstetrics & Gynaecology at CK Birla Hospital, Delhi, and Dr Sakshi Goel, Senior Consultant Obstetrics & Gynaecology at Rainbow Children’s Hospital, Delhi, the answer lies in hormonal changes and natural chemicals called prostaglandins.
The menstrual cycle is a carefully controlled process driven by hormones. Just before your period begins, levels of oestrogen and progesterone drop sharply.
This drop signals the body to shed the uterine lining, which leads to bleeding. But the shedding process involves strong muscular contractions of the uterus, and that is what causes cramps.
Here’s a closer look at why pain is severe on day one and usually improves by day four.
PROSTAGLANDINS PEAK ON THE FIRST DAY
Prostaglandins are hormone-like chemicals that help the uterus contract so it can shed its lining.
On the first day of menstruation, prostaglandin levels are at their highest. Higher levels mean stronger and more frequent uterine contractions. These intense contractions are the main reason cramps feel worse at the beginning of your period.
As the lining gets expelled over 24 to 48 hours, prostaglandin production decreases. By the third or fourth day, contractions are less intense, and so is the pain.
REDUCED OXYGEN TO THE UTERUS INCREASES PAIN
Strong uterine contractions can temporarily compress nearby blood vessels. This reduces blood flow and oxygen supply to the uterine muscles, a condition known as ischaemia.
When tissues do not get enough oxygen, they produce sharp, cramp-like pain. This is why the discomfort on the first day can feel intense and throbbing.
As contractions slow down in the following days, blood flow improves and pain reduces.
HEAVIER FLOW MEANS STRONGER CONTRACTIONS
Menstrual flow is usually the heaviest on the first and second days. The uterus needs to contract more forcefully to push out a larger amount of blood and tissue.
More force equals more discomfort.
By the fourth day, the flow becomes lighter. Since most of the lining has already been shed, the uterus does not need to contract as strongly. This leads to noticeable relief.
CERVICAL SIZE CAN ADD TO THE PRESSURE
In younger individuals, especially the cervix, the narrow opening at the lower end of the uterus may be relatively small.
As menstrual blood passes through this small opening, it can create added pressure and pain during the first day or two. Once the flow reduces, the pressure eases.
OTHER SYMPTOMS ALSO IMPROVE BY DAY FOUR
High prostaglandin levels do not just cause cramps. They are also linked to:
- Nausea
- Loose stools
- Headaches
- Lower back pain
- Pain spreading to the thighs
As prostaglandin levels drop by the third or fourth day, these symptoms usually improve as well.
WHEN ARE PERIOD CRAMPS NOT NORMAL?
Mild to moderate cramps are common. However, severe pain that disrupts daily activities may signal an underlying condition.
Doctors say you should seek medical advice if you experience:
- Cramps so severe that they cause vomiting or fainting
- Pain that gets worse every year
- Very heavy bleeding
- Little or no relief from painkillers
- Pain between periods
Conditions such as endometriosis, adenomyosis, or uterine fibroids can cause unusually painful periods and require proper treatment.
HOW TO MANAGE FIRST-DAY CRAMPS
Understanding why cramps are worse on day one can help you manage them better. Doctors recommend:
- Using a heating pad on the lower abdomen
- Taking prescribed pain relievers
- Doing light stretching or walking
- Staying hydrated
- Tracking your cycle to prepare in advance
Stress and poor diet can also worsen symptoms, so maintaining a healthy lifestyle may help reduce discomfort over time.
The first day of your period is usually the most painful because prostaglandin levels peak and the uterus contracts strongly to shed its lining.
By the fourth day, hormone levels stabilise, contractions weaken, and flow becomes lighter, bringing relief.
While this pattern is normal for many women, severe or worsening pain should never be ignored. Listening to your body and seeking medical advice when needed can make a big difference in managing menstrual health.
