Healthy New Jersey

Periods (menstruation)

Periods and pregnancy

Understanding the relationship between periods and pregnancy is important for people who are trying to conceive, are currently pregnant, or anyone sexually active. 

The menstrual cycle

The menstrual cycle is defined as the time between the first day of one cycle and the first day of the next cycle. The average length of a cycle is around 28 days, but varies from person to person.

The cycle begins when the level of a hormone, called estrogen, increases in the body. When that happens your ovaries will release an egg. The release of an egg is called ovulation.

During the second half of the menstrual cycle, the hormone called progesterone starts to increase. This hormone prepares the uterus for a possible pregnancy.

If you do not get pregnant, the levels of estrogen and progesterone in your body will drop. This drop in hormone levels will cause the lining of the womb to shed which causes a period. Find out more information on periods.

Phases of the menstrual cycle

There are four main phases of the menstrual cycle.


Commonly known as a period, menstruation is the start of the cycle when the lining of your uterus sheds and blood flows. Typically lasting three to seven days, your period contains blood, mucus, and some cells from the lining of your uterus. 

Pads, tampons, menstrual cups or discs, or period underwear can be used to absorb your period. Pads and tampons should be changed every three to four hours. Menstrual cups and discs should be changed every eight to 12 hours.

Find more information on period products.

Follicular phase

The follicular phase starts on the first day of your period and lasts for 13 to 14 days, ending in ovulation. During this phase, the pituitary gland in the brain releases a hormone to stimulate the production of follicles on the surface of an ovary. As the follicles develop, typically one becomes dominant and reaches maturity.

During this phase, your uterus lining thickens to prepare for a potential pregnancy. Changes also occur in the cervical mucus to make it more receptive to sperm in facilitating their journey toward the egg. 


Ovulation occurs when a mature egg is released from an ovary and moves along the fallopian tube toward your uterus. This occurs once a month, typically around the middle of the menstrual cycle, roughly two weeks before the start of your next period.

Ovulation is a brief process, typically lasting 16 to 32 hours. During this time, the egg is available for fertilization by sperm. If fertilization occurs, the fertilized egg can implant itself in the uterus, leading to pregnancy. After having sex, sperm can live for up to five days inside the fallopian tubes. If you do not want to get pregnant, use contraception.

Various factors can influence the timing of ovulation, including the length of the menstrual cycle and individual hormone variations. Tracking ovulation can be helpful for individuals trying to conceive or those wanting to understand their menstrual cycle better. It's not possible to get pregnant if ovulation doesn't occur. 

You're most fertile during ovulation

At the time of ovulation, you're at your most fertile. This period is known as the "fertile window." It usually lasts for 16 to 32 hours and happens around 14 days before your period starts.

Tracking ovulation

There are a few ways you can track your cycle to know when you're ovulating to plan a pregnancy. 

1. Keep a diary or mark the dates of your period on a calendar

Recording your menstrual cycles can help identify patterns and estimate when ovulation may occur. Many websites and apps offer menstrual cycle tracking tools that allow you to input your cycle length, period start dates, and other relevant information.

2. Use an ovulation calculator

Ovulation calculators are tools for estimation and not foolproof methods for pregnancy prevention or conception. It's always a good idea to consult with a health care professional for personalized guidance and advice.

3. Basal Body Temperature (BBT) Charting

Tracking your basal body temperature each morning before getting out of bed can help detect the slight rise in temperature that occurs after ovulation. There are dedicated BBT thermometers available, and many websites and apps provide BBT charting tools for easier tracking and analysis.

4. Ovulation Predictor Kits (OPKs)

These kits detect the surge in luteinizing hormone (LH) in your urine, which happens shortly before ovulation. OPKs are available in pharmacies and online, and some websites offer integration of these kits into their ovulation tracking features.

5. Cervical Mucus Monitoring

Observing changes in cervical mucus consistency and appearance can give insights into ovulation. Around ovulation, cervical mucus typically becomes clear, slippery, and stretchy, resembling raw egg whites. Tracking and noting these changes can be done manually or using online tools.

Luteal phase

After ovulation, the cells in the ovary known as the corpus luteum release progesterone and estrogen. These hormones play a vital role in creating the right environment within the uterus as it thickens in preparation for a potential pregnancy.

If a fertilized egg successfully implants in the uterine lining, the corpus luteum continues to produce progesterone, providing support to maintain the thickened lining.

However, if pregnancy doesn't occur, there's no need to worry. The corpus luteum dies, progesterone levels gently decline, the uterus lining sheds, and the period begins again.

Common menstrual problems

Common menstrual problems include

  • Premenstrual syndrome (PMS): Hormonal events before a period can trigger a range of side effects in menstruating people, including fluid retention, headaches, fatigue and irritability. Treatment options include exercise and dietary changes.
  • Dysmenorrhea: also known as painful periods. It is thought that the uterus is prompted by certain hormones to squeeze harder than necessary to dislodge its lining. Treatment options include pain-relieving medication and the oral contraceptive pill.
  • Heavy period (menorrhagia): If left untreated, this can cause anemia. Treatment options include oral contraceptives and a hormonal intrauterine device (IUD) to regulate the flow
  • Amenorrhea: also known as the absence of your period. This is considered atypical, except during pre-puberty, pregnancy, lactation, and postmenopause. Possible causes include low or high body weight and excessive exercise.

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