40 weeks may seem like forever while waiting for your bundle of joy, but when faced with the scenario of giving birth too early, 40 weeks is the perfect amount of time. Preterm labor and delivery is a scary situation and is there anything we can do about it? What are the actual risk factors for preterm labor and are they avoidable? A recent study, “Risk factors for preterm labor and delivery”, updated in June 2011, goes over the major risk factors of preterm labor and delivery. Some risks seem predictable like carrying multiples, while some are eye-opening — is diet to blame?
Previously going into labor early is the biggest indicator of subsequent preterm delivery (PTD). The body doesn’t protect itself after an initial preterm labor by holding on to the next pregnancy longer, but it sets the stage for additional early deliveries. A mother who has already had one baby born too early has about a 15% chance of delivering the second one early. Two preterm deliveries increase your risk of delivering preterm to 40%. Spontaneous abortion in the second trimester increases the risk of preterm labor the next time and the more pregnancies that have been terminated the greater the risk of spontaneous preterm delivery.
Multiple births increase the risk of going into labor early. The more babies there are the harder it is on the body as they grow and have increased demands for nutrients, oxygen and space. One of the biggest reasons preterm labor occurs with multiples is due to a complication like cervical incompetence; where the cervix begins to dilate and thin before it’s time to give birth. This is most likely due to pressure from the uterus itself. It’s unfortunately a common situation, the more babies you’re carrying the sooner your delivery date will be. Twins have an expected gestation of 37 weeks, and if carrying triplets or greater doctors want you to make it past 32 weeks.
Genetics play a role in preterm delivery. If a female relative (immediate) has had a preterm delivery than a woman’s odds increase. African American women have a greater risk of PTD than other nationalities. Chromosomal defects can happen in all women a specific one can, “involve altered genetic regulation of cervicovaginal cytokine production” (3) which could lead to a greater inflammatory effect on the mother’s vaginal microflora. This inflammation can lead to infection, another risk of PTD. Infection and inflammation anywhere in the body can travel to the uterus potentially compromising the pregnancy. A urinary tract infection or gum disease is one of the major culprits for spreading infection. Additional infections could be from the Group B streptococci bacteria or an STD like Chlamydia.
Physical Activity and Work
Physical activity and work are seen to increase the risks of preterm birth. Some studies have noted that work that involves long hours (greater than 45 hours a week), a high amount of physical activity like heavy lifting, or a poor work environment involving stress and noise increase the risk of PTD.
Smoking and Substance Abuse
There is an increased risk of preterm labor associated with smoking and substance abuse. The amount of cigarettes smoked a day directly increased the risk of preterm delivery. 9 cigarettes a day or less increased the chances of delivering early at 33-36 weeks, while 10 cigarettes a day or more increased the chances of delivering early to 32-36 weeks.
Most people may think a woman’s diet itself doesn’t play a huge role in preterm labor. Just increase the calories by 300 a day throughout the pregnancy and you’ll be fine. Especially during pregnancy it’s not just how much you eat, but what you eat. Interestingly, low amounts of omega-3 fatty acids found in seafood and some nuts were seen to increase the risk of preterm labor. A study looking at women who did not take fish oil supplements vs. those that did found a 7% increase in the occurrence of preterm labor.
Because my passion is nutrition and the ways it can change your life I found this next portion extremely interesting regarding preterm delivery and mother’s weight. In “Risk factors for preterm labor and delivery” the findings were inconclusive in whether a mother’s pre-pregnancy weight was a factor in preterm labor. For example an underweight pre-pregnancy mother may also have economic and demographic issues that lead to preterm labor (such as lack of health care), but being overweight before pregnancy has a greater risk of preterm labor due to medical complications. An interesting article, “Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses”, finds that “overweight and obese women have an increased risk of a preterm birth before 32 weeks, induced preterm birth before 37 weeks, and, accounting for publication bias, preterm birth before 37 weeks overall”. The implications of this study find that the risks for preterm birth, whether induced due to complications or spontaneous, from overweight mothers are potentially preventable.
Weight gain or lack of during pregnancy also increases the risks of preterm labor. Too little gained or too much weight gained can lead to a small of gestational age (SGA) or large for gestational age (LGA) baby, both coming with their own health issues. A small for gestational age baby may not be able to regulate his or her body temperature, have low blood sugar or may have decreased oxygen levels. A large for gestational age baby could suffer from low blood sugar also and may an increased incidence of birth defects.
There are many factors that can increase the risk of delivering early and if possible let’s avoid them all. It’s an excellent idea to stop smoking, drugs, heavy lifting when pregnant to decrease the risk of premature labor but don’t forget to pay attention to diet and exercise. Your weight, pre and post pregnancy, is an excellent representation of your nutritional status and this status plays a role in your developing child. Let’s make remembering to eat well throughout the pregnancy and maintaining a healthy lifestyle as important as quitting smoking or buckling your seatbelt.
- 1. Am J Epidemiol. 1992 Sep 1;136(5):574-83. Maternal nutrition and spontaneous preterm birth. Kramer MS, McLean FH, Eason EL, Usher RH. Department of Pediatrics, McGill University, Montreal, Quebec, Canada.
- 2. BMJ. 2010; 341: c3428. Published online 2010 July 20. doi: 10.1136/bmj.c3428
Copyright © McDonald et al 2010 Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses Sarah D McDonald, Zhen Han, Sohail Mulla, and Joseph Beyene. Knowledge Synthesis Group.
- 3. Risk factors for preterm labor and delivery Julian N Robinson, MD, Errol R Norwitz, MD, PhD, Charles J Lockwood, MD, Vanessa A Barss, MD. Uptodate.com