Pregnancy

Pregnancy due date chart

One of the most exciting things about being pregnant will be looking forward to your due date. That particular number and month will be etched into your mind from the time you first find out you are pregnant until your baby is actually in your arms.

You’ll make plans around your due date, use it as a marker for finishing work, completing renovations, moving house, moving your toddler out of the cot and into a bed; there’s really no end to the significance of your baby’s due date. And you won’t be the only one who’s interested either. You’ll find lots of people, even complete strangers asking “When is your baby due” – to the point where you may even consider placing a sign on your belly!

But your due date’s not just important for knowing when to expect your baby to be born. Using it as a reference point for your baby’s development, when it will be possible to hear their heart beat, the size of your tummy and general pregnancy progress will all be important. You’ll find that there will be date markers consistently through your pregnancy which help to guide you and your midwife or obstetrician as to whether your baby is growing as it needs to.

For example, most first time mothers first feel their baby’s movements from around 16 weeks of gestation and by 20 weeks of gestation the uterus has normally grown to the level of the mother’s navel. These and other indicators will all provide reassurance that you and your baby are progressing normally.

Your health care provider will check with you at each stage of your pregnancy how many weeks you are and when you are due. Matching this information with your tummy size provides an excellent way of ensuring your baby is growing and will be ready for birth at, or around, their due date.

Due date is not exact

It’s important to remember that your due date is not a guarantee of when your baby will be born. At best, it’s an estimate based on the average length of pregnancy for the average woman who has an average cycle. But who wants to be average?

Due dates are also worked out on the assumption that conception occurred sometime on the 14th day of a woman’s cycle. As we know, in the average mother this is likely to occur, but again there has to be some accommodation for all the millions of mothers who don’t fit into this thin spectrum of “average”.

How is the due date worked out?

To estimate a due date, 40 weeks or 280 days is added to the first day of a woman’s last menstrual period. The majority of babies will come either a few days before or after this date. Particularly for women having their first baby, it is very normal to go past their due date.

But then, just to confuse us, babies are still considered term or mature when they get to 38 weeks of gestation, or even when they decide to stay in the uterus for up to 42 weeks. This four week “window” allows for the differences in menstrual cycles between women – not every woman has an average 28 day cycle.

Some women are unsettled by the vagueness of the due date providing a likely time for their baby’s birth, not a guarantee. They would prefer an exact estimate with a definite “line in the sand” date to work around and towards. But babies who are ready to be born have their own mechanisms for initiating labour, and care little for what a due date calendar or chart says about when they should be born. Pregnancy is not an exact science or process which is under our ultimate control.

Needing to adopt a relaxed attitude about the due date is important. In truth, it’s probably a good practice for life with a newborn, where needing to be adaptable and to go with the flow is an essential part of getting through each day. Control and babies are two words which can’t really be used in the same sentence.

Due Date Calculator

Fill in your details below to calculate your due date:

* Please remember this result is only an estimate. Your baby will arrive when he/she is ready.
Do consult your healthcare provider to determine your correct due date.

Ultrasounds

It’s routine now for most pregnant women to have at least one ultrasound during their pregnancy. The first one is often done in the first trimester, especially if there is some doubt about the due date or weeks of gestation. The second is referred to as a pregnancy screening ultrasound and is done at around 18 weeks of gestation.

An early screening and date confirmation ultrasound can answer lots of questions about the baby’s maturity; where the placenta is positioned and the baby’s general health. It can also be used to assess the rate of the baby’s growth and if its size matches the weeks of gestation as the baby progresses towards their due date.

What if I’ve had IVF?

If you have conceived via IVF or fertility assistance, then it’s much easier to estimate exactly when conception occurred. Working out your due date from this point makes it easier to know for certain when you conceived, though this won’t take into account your baby’s individual rate of maturity. Some women seem to take longer or shorter times to “grow” their baby. In cases of multiple pregnancy, the likelihood of delivering before the due date is greater. Likewise if there are pregnancy complications, then premature labour is more likely.

But what about if my baby is born before my due date?

For women who have been diagnosed with pre-eclampsia, gestational diabetes or an auto-immune disorder, an induction of labour or caesarian section delivery may be recommended. In these cases, a benefit versus risk assessment is done to ensure the wellbeing of the mother is not compromised by extending the length of her labour. But just as importantly, the health risks to her baby of being born pre-term are also carefully considered.

When a baby is not growing as it needs to or is being compromised in some way, then delivery before the due date is often recommended. Conditions for the baby outside the uterus need to be better than for them to remain where they are. In this way, using the due date as a guide to inform decision making and weighing up all the factors is a vital part of overall obstetric management.