Menstrual cycle: understanding and calculating

If you want to become pregnant, it is important to know how your menstrual cycle works. In this way you can calculate when ovulation (ovulation) takes place and on which days you are most fertile, in order to increase the chance of a pregnancy how to get pregnant while tubes are tied without surgery.

Duration menstrual cycle

The menstrual cycle starts on the first day of menstruation and ends on the day before the first day of the next menstrual period. The length of the menstrual cycle varies per woman, but lasts an average of 28 days. Some women have an irregular cycle; this means that the period between the different periods always varies in length.

Menstrual cycle

First day menstrual cycle

Even though the duration varies per woman, a cycle always follows the same order. It always starts with bleeding, or: you have your period. The first day of your period is also held if you turn out to be pregnant to calculate when the baby is likely to be born. If you are trying to get pregnant, it is useful to keep up with this. The period of menstruation lasts between three and seven days for most women.

Calculate calculated date – handy tool

If you are pregnant, it is nice to know when you are due. This way you can prepare yourself mentally for delivery, but calculating a calculated date is also important for the midwife. How long have I been pregnant? On the basis of the gestational age, the midwife can see if your baby is developing well. There are different ways to determine your delivery date. Calculating your calculated date yourself is, with a regular cycle , fairly reliable. But only your doctor, obstetrician or gynecologist can calculate the exact calculated date. And then only 4% of the babies are actually born on this date.

How long have I been pregnant?

If you want to calculate your calculated date, you must first know how long you are pregnant. You can determine this by calculating the day of your ovulation . For that you need to know what the first day was of your last period. On the basis of the average length of your cycle you can thus determine when the ovulation took place. Add 40 weeks to this and you will know when your delivery will be around. There is sometimes confusion about the average length of a pregnancy. Is this now 38 or 40 weeks? That’s how it is. It is 40 weeks from the first day of your last menstrual period. This count is usually used to indicate how long you are pregnant. But from the moment of conception , a pregnancy lasts 38 weeks.

Calculate your calculated date yourself

You can therefore calculate your calculated date by adding 40 weeks (280 days) to the first day of your last period. With a regular cycle this method is fairly reliable, but it remains an indication and not an exact science. Your ovulation date depends on the length of your cycle. With a longer cycle, the delivery date will therefore be later than when you have a shorter cycle. This means that every day that your menstrual cycle is longer, your due date becomes a day later. With a handy calculator you can calculate your calculated date yourself. First add 40 weeks (280 days) to the first day of your last period. Every day that your menstrual cycle is shorter than 28 days, your calculated date will be one day earlier. For each day that your menstrual cycle is longer than 28 days, your due date will be one day later.

When is the calculation less reliable?

Again, with a regular cycle, this calculation is pretty reliable. But you can only determine the official calculated date by means of an echo. And then there is little chance that your baby will be born exactly on this day. Calculating your calculated date yourself becomes less reliable with:

an irregular menstrual cycle;

a menstrual cycle that is much longer or shorter than 28 days;

use of the pill;

Calculate the calculated date during the period echo

To determine your calculated date exactly, a deadline echo is performed. You usually get this right after the intake interview with the midwife. Sometimes the midwife can do this himself, but that is not always the case. In general, the period ultrasound takes place between 9 and 12 weeks of pregnancy. From this moment on, the gestational age can be determined with great accuracy. When you get the ultrasound depends on the first day of your last period and your cycle.

How reliable is the calculated date?

The calculated date gives a good indication of when your delivery will take place. Yet only about 4% of all women give birth exactly on this day. Most women give birth with a gestational age between 37 and 42 weeks. So that is 3 weeks before and 2 weeks after the due date. Knowing your due date is very important. On the basis of this, the midwife can see if your baby is developing well. You also know in this way whether the birth starts early or takes a long time. A birth before 37 weeks or after 42 weeks can cause risks.

When is the baby coming?

Many women become impatient at the end of their pregnancy: when will the baby come? It must be there before the end of your 42nd week of pregnancy, otherwise it is advisable to initiate delivery.

Average gestational age

 Your due date will be determined at the time  limit ultrasound. All unborn babies grow exactly the same for the first 12 weeks . A certified person can accurately determine how long you are pregnant with an ultrasound. Your calculated date is calculated based on this. But no one can predict if you will give birth exactly on that date. It all depends on you and your baby. It is an interplay between mother and child that starts the birth.

When give birth?

The big waiting for the birth has begun. True. Remains. That. Baby?! Do not worry. Only 4% of Dutch women give birth on the due date. Most pregnant women give birth with a gestational age between 37 and 42 weeks. So that is between 3 weeks before and 2 weeks after the due date. You will only be overtime if you are more than 42 weeks pregnant .

Will the baby still be able to get out?

And that child just grows in there. Can he still look normal at all? For reassurance: an elephant carriage does not mean that you also give birth to an elephant. A child grows in the belly in the last period only about 150 to 200 grams per week, so that is not so bad. You don’t have to expect a giant, barring exceptions.

Does the birth begin?

Losing your mucus plug can be a sign that the birth is starting, but it can also take another 2 weeks. The cervix is ​​closed during pregnancy by a mucus plug. When the uterus stretches, the mucus plug comes loose. That is accompanied by some blood loss. A good sign, but you don’t have to call the midwife immediately. (Well if you continue to bleed and get pain, or if you feel less movement .) The fact that your baby has descended does not mean anything: it can take weeks before it comes.

Broken webs; delivery starts

If the membranes break , the birth will in theory begin. But when the baby actually comes, it is due to contractions. This sometimes takes a while. If it takes longer than 24 hours for the contractions, the risk of infection in the baby increases and you are transferred to the gynecologist. The baby is then better monitored and often antibiotics are given during delivery to reduce the risk of infection again.

Generate the birth yourself

A lot of fables are circulating about what you can do to make the birth start faster . Like eating the heart of a pineapple, drinking castor oil or offering yourself a spicy meal. That all influences the functioning of your intestines and sometimes that can give the uterus a boost, but it is not scientifically substantiated.

Does sex help to give birth?

Having sex is the same kind of story. Sperm contains progesterone (propagandist) and that medicine is sometimes also used in the hospital to soften the cervix. Only: there is only a small amount of progesterone in sperm, so the effect is minimal. If you get an orgasm during sex, your womb will contract. That can help, but don’t expect too much from it.

Stripping or pricking?

Acupuncture and foot reflexology massage helped a number of pregnant women in my practice. But that may also have been psychological. Stripping the cervix is the only ‘natural’ substance that can give birth. The midwife then tries to carefully unwind the membranes from the cervix; the treatment is most similar to measuring the digestion. If it succeeds, a hormone is released that can cause cramps, which in turn cause contractions. Stripping alone does not always have an effect. If stripping is unsuccessful, the midwife or gynecologist will have a trick that your baby may not have gotten back to: the membranes break . They are then punctured with a sort of crochet hook, after which delivery in theory starts within 24 hours.


That child can bother what he wants, but eventually he ‘loses’ it. In the Netherlands you are introduced after 42 weeks of pregnancy with the intention of having your baby born as soon as possible. The birth is then called medical, which means that it is (in principle) done in the hospital and under the supervision of a gynecologist. After 42 weeks the placenta starts to function less well, which means that your child is gradually better off outside the abdomen. Upon introduction , the cervix is ​​stimulated with a hormone gel or balloon that is inserted. Cramps are induced that cause contractions or at least prepare the womb for action. Contraindications via an infusion can give the last push.

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