40 Weeks pregnant: Baby development, symptoms and signs

Your body at week 40

Contractions

At week 40, your Braxton Hicks contractions might be getting stronger, more intense, or coming more often. It might become difficult to decide whether these are false contractions or labor contractions. Remember that Braxton Hicks contractions can last anywhere from 30 seconds to 2 minutes, while labor contractions will consistently last around a minute [1]. Labor contractions also come at regular times intervals and at a quicker pace as labor progresses, while Braxton Hicks contracts will be irregular. Finally, Braxton Hicks contractions can go away completely while labor contractions won’t.

You might have read about another type of “false labor”, known as prodromal labor. Prodromal labor can be difficult to distinguish from labor (or “real”) contractions, because prodromal contractions can come at regular intervals and feel very much like the “real thing” [2]. Prodromal labor contractions, however, will stay at the same interval and intensity rather than get stronger or come at a quicker pace. 

If you are unsure and have any suspicions you might be in labor, contact your midwife or doctor. It is better to be sure, and only your healthcare provider can check to see if your cervix is dilating, which is the best indication of labor’s progression. Remember to keep track of your contractions by writing down the timing between intervals, as well as how long they have been going on.

Back pain

Back pain during pregnancy is often caused by a number of factors — changes to your posture on account of your large belly, hormones that make your back and pelvis feel weaker, the pressure of your uterus on your pelvis, and general tiredness [3]. Try to maintain good posture, with your head tall, shoulders pulled back and down, and pelvis slightly tilted forwards when sitting and standing. You can also physically support your bump with your hands or a support belt when you are standing. You can also try light gentle exercise like swimming or walking (if safe to do so in your pregnancy).

Back pain can also accompany labor contractions, known as back labor. Back labor is pain, discomfort, and even cramping in your lower back that is usually most painful during a contraction but also lingers between contractions [4]. If you are experiencing back labor at home or in the hospital, try walking, sitting on a birthing ball, or tilting your pelvis back and forth to provide relief. If you are in the hospital, or a maternity center, tell your healthcare team so they can help you try to find a more comfortable position.

Your baby’s development at 40 weeks

At 40 weeks, your baby is full term, fully developed, and ready to be born. You might be wondering how big they will be and what they will look like. While your healthcare team has likely been trying to estimate their size based on ultrasounds and measurements of your stomach, it will be impossible to know their exact size until they are born. This week, your baby is probably around 19 to 21 inches long (48.3 to 53.3 cm) and weighs between 6.75 and 10 pounds (3 to 4.5 kilograms) [5].

All newborns will look slightly different, with different amounts of hair and vernix, which is the white substance that protects neonatal and newborn skin in the uterus and just after birth [6]. Right after birth, most babies will look reddish-purple, changing to red or pink after they begin breathing on their own [7]. Their heads can also seem a little oddly shaped, which is the result of the skull moving through the birth canal. This is completely normal, and their heads will return to their natural shape usually by the end of the first week [7]. Your baby also might have little white bumps on their nose, cheeks, chin, and forehead, known as milia.

Signs of labor at 40 weeks

At this point, you are likely anxiously waiting for any signs of labor. Discharging your mucus plug, contractions, and rupture of membranes (known more commonly as your water breaking) are the main signs of early labor. You might also experience a backache and the need to go to the bathroom. If you are already experiencing an increase in discharge, you might not notice if you discharge your mucus plug. Be on the lookout for any streaks of blood or slightly pink-tinged mucus. However, if you experience any bleeding, contact your healthcare provider right away.

Though only a small percentage of women experience their water breaking before contractions begin (when this happens, it’s called a premature rupture of membranes), it’s probably the most well-known labor symptom. That said, it might not always be obvious that your water has broken! When your water breaks, the amniotic fluid can come out as a slow, steady trickle or a larger rush of liquid. Amniotic fluid tends to be thinner than discharge, with a water-like consistency that can be clear, pink, or yellow. If you already feel like you need to pee all the time, it might be hard to determine whether your leak is urine or amniotic fluid. While urine can be stopped using your Kegel muscles, you will have no control over any leak of amniotic fluid. If you suspect you might be leaking amniotic fluid, even if you aren’t completely sure, it’s best to check with your nurse, midwife, or doctor.

Is it normal to still be pregnant at 40 weeks?

What happens if labor doesn’t start on its own?

It is widely estimated that only around 5% of babies are actually born on their due date, so try not to place too much importance on that particular day. In the US, statistics indicate that around 55% of babies are born in weeks 39 and 40, while around 5% of babies are born after week 40 [8]. Remember that week 40 begins with your due date — you are only considered past due starting 1 whole week after your due date passes. Doctors and scientists still don’t understand why labor begins when it does, or why some babies are born early or late. 

You might be eager to go into labor, but be wary of home or natural remedies. Unfortunately, there is no scientific or medical evidence that you can induce labor yourself. Some suggestions you might see, like exercise or sexual intercourse, are not proven to induce labor but are considered safe unless unadvisable during your pregnancy. However other suggested methods you might read about may actually cause harm to you or your baby [9]. 

In weeks 39 or 40, your doctor or midwife might offer a membrane or cervical sweep, to help encourage your body to begin labor naturally. In this procedure, a doctor or midwife will use their finger to physically separate the membrane of the amniotic sack from your cervix. Some may find this uncomfortable or painful, and you might experience cramping or bleeding afterward.

While most doctors recommend letting labor begin naturally [10], sometimes it becomes necessary to induce labor medically, or artificially. This can happen if you are overdue, if your waters break but labor is not beginning on its own, or if you or your baby have a health problem [10]. There are two main methods for labor induction: hormonal and physical. Let’s break down what these two methods entail:

• Hormonal induction: certain hormones, usually prostaglandin or oxytocin, will be given to you either as a suppository in your vagina, a gel, as tablets, or through an IV [11]
• Physical induction: a device such as a balloon catheter (a small, water-filled balloon) or a dilator can be used to widen your cervix. In some cases, your amniotic sack will be broken (artificial rupture of membranes) to encourage your body to produce more prostaglandin and speed up contractions.

If you require induction, it might affect where you can give birth or require you to be in the hospital longer. Some women who are induced also experience more painful labor, so keep communicating with your healthcare team if you require pain relief. Induction does not restrict your pain relief options during labor [9]. 

Tips in week 40

• Take it easy: resting as much as you can in these final days of your pregnancy can help you physically and mentally prepare for childbirth and the big changes that will happen after your baby is born. 
• Try some breathing exercises: breathing exercises can help you relax and you can also use them during labor to help you manage your pain. Try focusing on taking slow, deep breaths in through your nose and exhaling out through your mouth. Practice counting the length of your inhales and exhales, trying to make them as long and equal as possible.
• Learn about what happens to your baby after delivery: learning about the benefits of skin-to-skin contact and what the doctors and midwives will check after your baby is born can help you feel more comfortable in the delivery room.
• Consider a waterproof mattress cover: whether you are waiting for your water to break, or you are planning ahead for messes and spills, it might be a good time to get a waterproof mattress cover for your bed.
• Gas up and charge up: labor can begin at any time, so make sure that there’s enough gas in the tank of your car or your EV’s battery is fully charged. It’s also a good time to make sure that phones and tablets are charged, and double check that you have packed chargers in your hospital bag.

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