How does pregnancy occur?
Each month during a woman’s menstrual cycle there is a fertile time after ovulation (when an egg is released from an ovary) when it is possible for her to become pregnant.
(For more detailed information refer to the menstrual cycle section.)
This is the first day of the menstrual cycle and if a woman is not pregnant, the period begins.
Bleeding from a period has usually stopped by now.
Hormones cause the now fully grown egg to burst out of the follicle and leave the ovary. This is called ovulation.
The egg travels down the tube towards the uterus.
|A fertilised egg will then move down the tube and attach to the wall of the uterus where it will continue to grow into a baby.|
When is the fertile time of the menstrual cycle?
A woman is only fertile for a few days a month; this is usually around day 14-15 of the menstrual cycle (if the cycle is 28 days).
Once an egg is released from the ovary it can live for only 24 hours.
Sperm can live for up to 72 hours so it’s possible for a woman to have sex before ovulation and become pregnant.
Signs of the fertile & non-fertile times
Some women will feel ovulation (when the egg is released from the ovary) which might feel like an ache or pain in the area of the ovary.
The mucus produced by the cervix changes when the hormone levels change during the menstrual cycle.
When a woman is most fertile the mucus in the vagina becomes clear, slippery and stretchy (like raw egg white). At this time the vulva or entrance to the vagina feels soft and swollen.
When it is a non-fertile time the vulva and vagina can feel dry and vaginal mucus is more sticky. At this time a plug of mucus blocks the cervix preventing sperm from entering.
How long will it take to get pregnant?
To get pregnant it is necessary to have sex around the time of the month when the woman is ovulating. The chance of getting pregnant can be affected by several factors related to both the man and the woman including: age, weight and whether either smoke or drink alcohol.
Figure 2: Proportion of women likely to get pregnant over 2 years
For a couple to be fertile, the woman would not have any condition that might stop her becoming pregnant and the man would not have problems producing sperm. If a couple is fertile and trying to have a baby, most women (up to 85%) will get pregnant within a year if they are having sex regularly and not using contraception. Up to 95% will get pregnant within two years. These are averages, some women will get pregnant quickly and some will take longer.
Age & fertility
- At age 25 years, only 5% of women take more than a year to get pregnant
- Starting at about age 32 years, a woman’s chances of conceiving decrease gradually but significantly
- From age 37 years, a woman’s fertility decline speeds up
- By age 35 years, 30% of women take more than a year to get pregnant
- By age 40 years, fertility has fallen by half 
If a woman has been trying to get pregnant for more than a year she should see a doctor. If she is over 35 years old she should see a doctor if she has been trying for six months or more.
Planning for pregnancy
Having a pre-pregnancy health check
It's a good idea for a woman to see a doctor or women's health nurse before pregnancy to check how to prepare for a healthy pregnancy and to reduce the risk of problems for her and the baby.
Below are some things a woman should to think about before she stops contraception and starts trying to get pregnant.
There are many things that can be bad for a baby’s growth and development in-utero including whether the mother is significantly overweight or underweight, the effects of smoking, alcohol, some medications, caffeine and the amount of exercise the mother does). If possible, it is best to make any changes necessary to these factors before becoming pregnant.
There is no safe time for a woman to drink alcohol during pregnancy. Alcohol passes through the placenta from the mother to the baby and can cause serious problems in the baby’s development. The Australian alcohol guidelines say that for women who are pregnant or planning a pregnancy, the safest option is not to drink alcohol. If a woman is planning to become pregnant, it is safest to stop drinking alcohol during this time to reduce the chance of exposing the baby to alcohol before she knows she is pregnant. It is possible men’s fertility may also be affected by alcohol as well as their long term health so it is probably best for men to have no more than two standard drinks a day.
Smoking during pregnancy is thought to be the biggest cause of the development of complications during a pregnancy. Cigarette smoke contains many chemicals and can cause long-term damage to the lungs, brain and blood of an unborn baby. Smoking can also cause pregnancy emergencies in the mother, by reducing the amount of oxygen and nutrients an unborn baby needs for healthy growth. It can cause an increased risk of pre-term birth and low birth weight which can increase risk of kidney disease, diabetes and heart disease in later life.
It is also important that a woman who is pregnant or planning a pregnancy does not smoke, marijuana or use other drugs.
It is also dangerous if a pregnant woman, who doesn’t smoke, has a partner who does because she will be breathing in tobacco smoke. Breathing second hand smoke can also harm the unborn baby and can increase the risk of sudden infant death syndrome in young babies.
A healthy, balanced diet with adequate calcium, iron, protein, zinc, folate (known as folic acid when it is added to foods), iodine and other nutrients is important to the health and growth of the baby. Research has shown that the food a mother eats during pregnancy can affect the development of her baby, and may also affect the baby’s health later in life. If a woman is not able to get enough nutrients from her diet, then a multivitamin supplement may be necessary.
Folic acid is recommended for all women once they stop using contraception in preparation for pregnancy to prevent birth defects such as spina bifida.
Folic acid can be taken as a supplement on its own or as part of a multivitamin. A minimum 400mcg is needed and higher doses (5mg) for women at higher risk such as those with diabetes, a previous history of children affected by spina bifida or other neural tube defects.
Folate is found in in leafy green vegetables, asparagus, broccoli, lentils, chickpeas and a range of other vegetables and grains. In Australia, the flour used to make bread has folic acid added to it.
Caffeine can also affect an unborn baby; it is not recommended that women have more than 200mg of caffeine a day while pregnant (this is about the same as in an espresso or cappuccino, two mugs of instant coffee or four cups of tea).
Anaemia (a lack of iron) is more common in Indigenous women in pregnancy and an iron supplement may be required.
It is helpful for a woman to begin her pregnancy with a healthy weight. It will reduce the risk of her developing gestational diabetes and improve the chances of a healthy pregnancy. Being underweight and overweight can also reduce a woman’s fertility or chance of getting pregnant.
Regular exercise such as walking, before and during pregnancy will help prevent excessive weight gain. This can help reduce the risk of developing gestational diabetes and assist a woman to maintain good health during the pregnancy. It is important not to overheat while exercising in pregnancy so women shouldn’t exercise to the point of heavy sweating or exhaustion and should reduce exercise levels on hot and humid days.
It is important for a woman planning a pregnancy to make sure that all her immunisations are up to date. If conditions such as measles, mumps, rubella, varicella occur during pregnancy, they can cause birth defects.
Sexually transmissible infections (STIs)
It is important to treat and manage any STIs before pregnancy to increase the chances of a healthy pregnancy and delivery.
Cervical (Pap) screening
It is important to have a Pap test done before planning pregnancy so that if there are any abnormalities treatment can be completed prior to pregnancy. An abnormal pap screen result cannot be treated during pregnancy.
Women should check if they are taking medications to manage any health conditions such as blood pressure, epilepsy or kidney disease, that they are safe to take during pregnancy. It’s important to do this before becoming pregnant in case a substitute medication is required.
Any health conditions such as diabetes, hypertension, rheumatic heart disease or thyroid conditions will need to be well managed and controlled before and during pregnancy. This will be important to both the health of the baby and the mother. These conditions and their management should be discussed with the doctor as part of planning a pregnancy.
The Australian alcohol guidelines
This web page is designed to be informative and educational. It is not intended to provide specific medical advice or replace advice from your health practitioner. The information above is based on current medical knowledge, evidence and practice as at October 2013.