Have you had a sneaking suspicion that your contractions get worse* at night? Maybe it feels like your pregnant body just wants to find another way to wake you up in the middle of the night. Maybe you haven’t felt them but wake up on feeling like you just ran a marathon.
If you fall into the category of “most women”, you are probably correct – your body is working overtime, you are having more contractions at night.
Contraction frequency peaks between 8:30-2am.
The middle of the night is when contractions tend to kick in the most. Research shows that contraction frequency tends to peak, on average, between the hours of 8:30-2am. Luckily, you should get a break when the sun comes out – the uterine muscles tends to be take it easy during morning hours [1].
But why would you have more contractions while you sleep? The most likely culprit – your hormones!
Hormones = More Contractions at Night
At night, the hormones that increase the contracting nature of your uterine muscle – estrogens and prostandins – predominate [1]. And oxytocin and melatonin hit their peak at night too[2].
You may be familiar with oxytocin – the main hormone that stimulates your uterine muscle to contract. Melatonin is, in many ways, the buddy hormone for oxytocin[3]. And melatonin is a fascinating one to consider as the gangleader for night-time contraction-inducing hormones since the brain only releases melatonin in the dark (read: while you are sleeping).
How melatonin levels relate to your contractions at night comes down to it’s interaction with oxytocin. As oxytocin’s buddy hormone, melatonin helps oxytocin work more efficiently to increase contraction frequency[4]. Towards the end of your pregnancy, your body starts to produce more melatonin and more melatonin receptors in the uterine muscle[5]. This means that not only is your body bathed in more melatonin during those last few weeks of pregnancy but your body’s ability to respond to melatonin also increases as the big day approaches.
More oxytocin + more melatonin = more contractions.
Overnight contractions = your body getting ready?
Most likely, these contractions are non-labor contractions (also called Braxton Hicks contractions) that are helping your body “warm-up” for the big day.
But they may also signal when things are getting ready to go. One study has suggested that night-time contractions kick up a notch in the days leading up to delivery. Researchers on that study found a “nocturnal surge” in contraction frequency between 4-7am that might be predictive of labor. Women who delivered babies at term (37+ week), showed the surge pattern starting as early as 80 days before baby’s birth[6].
*Keep in mind that contractions can also increase if you are stressed or dehydrated. If you are experiencing more contractions than normal, try upping your water intake during the day and go easy on yourself.
REFERENCES:
[1] Zahn, V., and W. Hattensperger. 1993 “Circadian Rhythm of Pregnancy Contractions”. Z Geburtshilfe Perinatol. 197(1):1-10.
[2] Serón-Ferré M, et al. 1993. “Circadian Rhythms during Pregnancy.” Endocr Rev. 14(5):594-609.
[3] Sharkey, James T., Roopashri Puttaramu, R. Ann Word, and James Olcese. 2009. “Melatonin Synergizes with Oxytocin to Enhance Contractility of Human Myometrial Smooth Muscle Cells.” The Journal of Clinical Endocrinology and Metabolism 94 (2). The Endocrine Society: 421.
[4] Reiter, Russel J., Dun Xian Tan, Ahmet Korkmaz, and Sergio A. Rosales-Corral. 2014. “Melatonin and Stable Circadian Rhythms Optimize Maternal, Placental and Fetal Physiology.” Human Reproduction Update 20 (2): 293–307.
[5] Voiculescu, S. E., N. Zygouropoulos, C. D. Zahiu, and A. M. Zagrean. 2014. “Role of Melatonin in Embryo Fetal Development.” Journal of Medicine and Life 7 (4): 488–92.
[6] Alfredo M., et al. 1993. “Relationship of Circadian Rhythms of Uterine Activity with Term and Preterm Delivery.” American Journal of Obstetrics and Gynecology 168 (4): 1271–77.
