Weather changes and pregnancy

Weather and labor

Have you ever heard of someone say, “Wow, the emergency room was hopping last night.  It must have been a full moon.” Or “If your due date comes close to a full moon, that is when you’ll have the baby.”  Is this documented and evidence-based or simply Urban Legend.

While there is no single point of agreement among medical professionals, many recognize that barometric pressure affects physical conditions in the human body.  Dr. Leiber’s study (J Clin Psychiatry. 1978. May 39(5): 385-92), postulates “the existence of a biological rhythm of human aggression which resonates with the lunar synodic cycle.”  Conditions most commonly associated with changes in barometric pressure involve chronic pain and joint problems, but many pregnant women report being affected by changes in air density in other ways, including nausea, gas and headaches. Others claim that barometric pressure can affect labor pain, and some evidence exists to suggest a sudden change in barometric pressure can even induce premature labor.

So, the question of the day is, does a change in the weather or a full moon trigger labor?

The Full moon and labor

There are plenty of us that believe in the power of the full moon when it comes to triggering labor.  Especially those giant orange full moons.  We (the OB techs, nurses and doctors I work with) joke about “there’s no room at the inn” on such nights.

There are published works that show that there is such a relationship. One study looked at 5,927,978 French births occurring between the months of January 1968 and the 31st December 1974. Using spectral analysis, it was shown that there are two different rhythms in birth frequencies: –a weekly rhythm characterized by the lowest number of births on a Sunday and the largest number on a Tuesday and an annual rhythm with the maximum number of births in May and the minimum in September-October. A statistical analysis of the distribution of births in the lunar month shows that more are born between the last quarter and the new moon, and fewer are born in the first quarter of the moon. The differences between the distribution observed during the lunar month and the theoretical distribution are statistically significant.

People are 80% water.  And the changes in barometric pressure changes tides…does that change how we act or react?  Some say yes, others no.  Those that say no site the power of folklore/tradition/urban legends, misconceptions and cognitive biases (all bad events don’t occur during the full moon and all events that occur during the full moon aren’t bad!).  Talk to nurses who work labor and delivery on a regular basis, midwives,  busy doulas or experienced childbirth educators and they will all tell you that they believe in the power of the full moon plus changes in barometric pressure from cold/warm fronts.  I can tell you from personal experience, more often than not, full moons equal a full labor and delivery unit.

Examined was the relationship between lunar position and the day of delivery and the synodic (in astronomy, length of time during which a body in the solar system makes one orbit of the sun relative to the earth) distribution of spontaneous deliveries, especially in relation to the presence of a full moon. A retrospective analysis of 1248 spontaneous full-term deliveries in three-year period (36 lunar months) was done at the Department of Obstetrics and Gynaecology, Civil Hospital, Fano (Marche, Italy). The results showed a connection between spontaneous full-term deliveries and the lunar month. The effect of the phases of the moon seems to be particularly relevant in mothers who had birthed before.

What is barometric pressure and what role does it play in triggering labor?

Barometric pressure, also referred to as air pressure or atmospheric pressure, is the weight of the Earth’s atmosphere on the surface at a given location. It is dependent upon the amount of air above a location, and consequently, drops as one ascends higher while flying on an airplane.

To determine whether there is any correlation between sudden decrease in barometric pressure and onset of labor, a non-experimental, retrospective study at a 948-bed tertiary care hospital was done. Pregnant patients of 36 weeks gestation or more who presented with spontaneous onset of labor during the 48 hours surrounding the 12 occurrences of significant drop in barometric pressure in 1992 were included in the study. Significantly more occurrences of onset of labor were identified in the 24 hours after a drop in barometric pressure than were identified in the 24 hours prior to the drop in barometric pressure (P < 0.05). Therefore, the overall number of labor onsets increased in the 24 hours following a significant drop in barometric pressure.

Premature Membrane Rupture

• Barometric pressure changes are thought to possibly affect premature rupture of the membranes.  In 1985, the Journal or Reproductive Medicine reported a significant increase in obstetric complications in women thought to be affected by barometric pressure changes, resulting in premature rupture of the membranes and labor. The study found that evidence suggests an influence of barometric pressure on pregnancies that are notable near the end of term. Although no definitive proof of this effect has been made, the effects of barometric pressure on other physical conditions lend credibility to this claim.  One hundred nine patients with this obstetric complication lived within an area small enough to be subject to the same barometric pressure changes; onset of labor was used as a comparison point in 109 control patients. The two groups did not differ when demographic data were compared. There were no differences in other obstetric complications or neonatal outcome. There was a significant increase, however, in premature membrane rupture within three hours after a fall in barometric pressure. No such increase in the onset of labor was seen in the control group.

Labor Pain

• The functioning of the autonomic nervous system, which controls labor pain, can be heightened or deadened by changes in weather and environmental changes. Other functions of the autonomic nervous system include control of heart rate, respiration rate, perspiration and micturition which, if significantly changed, can also affect the comfort and safety of the mother during delivery.

Joint Ache and Pain

• As with other conditions affected by changes in barometric pressure, such as arthritis and MS, chronic pain in the legs and lower back due to increases and shifts in body weight may increase with changes in barometric pressure and other atmospheric conditions. Changes in the density of the air can be responsible for expansion and contraction within the joints, leading to new pain or more intense existing pain due to these changes.

Aggravation of Existing Conditions

• Other side effects of pregnancy include headaches, migraines, nausea, gas and intestinal discomfort. These are all common symptoms of pregnancy that can affect the mother at various times throughout the pregnancy. All of these conditions are normally influenced by the weight of the atmosphere and can increase in intensity due to environmental changes such as barometric pressure.

Bottom line, some maternity units actually have more staff available during periods of full moon.  I can tell you from personal experience, triage is at least a very happening place.  I’ve noticed that expectant mothers often experience false signs of labor during full moon.  Over the years, many researchers have sought to determine whether more babies are born during full moons than at other times of the month — often with contradictory or inconclusive results.  While the growing moon may not hasten the arrival of that little bundle of joy, an incoming storm might.  One study I read stated that on days with a larger change in barometric pressure, regardless of whether it was increasing or decreasing, the number of deliveries increased and the relationship was statistically significant.

I’ve decided throughout the rest of the year, I’m going to keep note of what happens on my unit delivery wise in relationship to the phases of the moon and weather changes.  I can tell you that over the last few nights, between going from 70 degree weather to tornados to several inches of snow on the ground in less than four days, our unit was hopping!