Lifestyle Considerations for Multiple Pregnancy
Nathan S. Fox
Introduction
Currently, twin pregnancies represent approximately 3% of all births in the United States. Women with multiple pregnancies are at increased of nearly every pregnancy complication, most notably preterm birth and fetal growth restriction, but also hypertensive disorders of pregnancy, gestational diabetes, congenital anomalies and stillbirth.
Twins are at increased risk of neonatal morbidity and mortality, mostly due to preterm birth, growth restriction and congenital anomalies. Despite the knowledge that multiple pregnancies are at higher risk of these complications, efforts aimed at reducing these risks have mostly not been effective. In unselected twins, the use of cerclage, pessary, bed rest and tocolysis have not been shown to reduce the risk of preterm birth or neonatal morbidity or mortality.This chapter focuses on twin pregnancy given the paucity of evidence-based literature for triplets and higher-order pregnancies. To some degree, the advice given can be extrapolated to higher-order pregnancies on a common-sense basis, with perhaps more limited expectations for exercise and travel. Regarding lifestyle modifications for women with twin pregnancies, there are unfortunately few evidence-based recommendations even for singleton pregnancies. Therefore, aside from recommending folic acid to reduce the risk of neural tube defects, avoidance of alcohol and other potentially teratogenic exposures, avoiding injury and infections and staying current with vaccination recommendations, it is difficult to make lifestyle recommendations based on high-quality evidence to any pregnant woman, let alone one with a twin pregnancy.
Yet pregnant women do seek this information and increasingly they will turn to other sources online, in the lay press or from friends and family. While this is not problematic per se, it is important for obstetricians, midwives and other prenatal providers to let pregnant women with twins know what we do know and what we do not know, and at least what our best advice is under the circumstances.
Nutrition and Weight Gain
The Facts (What We Know)
The National Academy of Medicine published gestational weight gain recommendations for women with twin pregnancies, based on the pre-pregnancy body mass index (BMI):
• BMI < 18.5 kg/m2 (underweight): No recommendation made due to insufficient data.
• BMI 18.6-24.9 kg/m2 (normal weight): 37-54 lb (16.8-24.5 kg).
• BMI 25.0-29.9 kg/m2 (overweight): 31-50 lb (14.1-22.7 kg).
• BMI 30.0 kg/m2 or higher (obese): 25-42 lb (11.4-19.1 kg).
A few things should be noted regarding these recommendations. First, these recommendations were not based on high-quality studies demonstrating improved outcomes with these weight gain parameters, but rather on how much weight most women with twin pregnancies gain. In fact, the specific recommendations simply represent the 25th to 75th percentile for women with twin pregnancies. Second, these recommendations assume a pregnancy of 37-42 weeks. Therefore, for women with a normal prepregnancy BMI, the recommendation of 37-54 lb weight gain over pregnancy comes out to at least a pound per week. Since many women have difficulty gaining much weight in the beginning of pregnancy, this could be difficult to achieve without significant effort. Third, the recommendations do not address when it is best to gain weight in pregnancy. Are there times in pregnancy when weight gain is more important, or is it best to have a steady weight gain, or does it not matter? Finally, it is also possible that weight gain is a sign of a healthy pregnancy and not a cause of a healthy pregnancy. Even if a certain amount of weight gain might be associated with good outcomes, it does not necessarily follow that manipulating a woman's weight gain (increasing it or decreasing it) to fall within these windows will actually cause improved outcomes. This is a shortcoming of all observational studies.
Despite the lack of high-quality evidence used to derive these recommendations, several studies have examined these recommendations retrospectively and have shown that in women with twin pregnancies, achieving these weight gain recommendations is in fact associated with many improved outcomes.
Achieving the minimum amount of weight gain is associated with a decreased risk of fetal growth restriction and a decreased risk of preterm birth. For example, we have published several retrospective studies of our own twin pregnancy experience and have consistently found a positive association between average weekly weight gain and improved outcomes in twin pregnancies. In our first study in 2010, we examined weight gain in 297 twin pregnancies and found that women with normal prepregnancy BMI who met the minimum weight gain guidelines were at significantly decreased risk of preterm birth < 32 weeks and fetal growth restriction and delivered babies with larger birthweights.1 On the opposite end of the weight gain spectrum, in 2011, we published a study of 170 women with twin pregnancies who delivered at 37 weeks or greater and found no adverse outcomes associated with excessive weight gain as defined by the guidelines.2For women with pre-pregnancy overweight or obese BMI, we also found that achieving the recommended weight gain was associated with improved outcomes. In a study of 252 overweight or obese women with twin pregnancies, women who achieved the minimum recommended weight gain had lower rates of spontaneous preterm birth, preterm premature rupture of membranes and fetal growth restriction.3 Adequate or excessive weight gain was not associated with an increased risk of pre-eclampsia or gestational diabetes.
In our first attempt to study the timing of weight gain in twin pregnancies in 2014, we published a study of 382 women with twin pregnancies and a normal pre-pregnancy BMI and found that weight gain from before pregnancy to 16 weeks had a significant association with preterm birth.4 In this study, the risk of spontaneous preterm birth < 32 weeks increased significantly with poor weight gain from before pregnancy to 16 weeks (Table 27.1).
Table 27.1 Weight gain from before pregnancy to 16 weeks
Risk ofspontaneous preterm birth < 32 weeks in twin pregnancies, based on the weight gain from before pregnancy to 16 weeks of gestation
The results of this study were unexpected as we did not expect to find such a strong correlation between early weight gain and spontaneous preterm birth and we could not identify a confounding factor to explain these findings.
However, since this was a retrospective study, it is uncertain if efforts to increase weight gain early in a twin pregnancy would be successful in reducing preterm birth, or even if they would be successful in actually achieving more weight gain.In a larger follow-up study on gestational weight gain patterns, we examined weight gain in 609 women with twin pregnancies and a normal pre-pregnancy BMI.5 We found that maternal weight gain from 0 to 16 weeks and from 16 to 24 weeks was most associated with improved fetal growth, whereas maternal weight gain from 24 weeks to delivery was most associated with a reduced risk or preterm birth.
In 2003, Barbara Luke and colleagues published outcomes for twin pregnancies managed in the Michigan Multiples Clinic, a specialised prenatal clinic for women with twin pregnancies that included the following:6
• Twice-monthly visits that included meeting with a registered dietician and a physician.
• Additional maternal education.
• Modification of maternal activity (work leave by 24 weeks, decreased strenuous activities).
• Individualised dietary advice.
• Multi-mineral supplementation.
• Serial monitoring of nutritional status.
The dietary and weight gain advice was comprehensive. For example, for women with a normal pre-pregnancy BMI, the recommendations included an intake of 3,500 calories a day and weight gain of 1.0-1.75 lb/week based on the gestational age. They published outcomes for 190 women with twin pregnancies enrolled in this programme compared to 339 women with twin pregnancies who were not enrolled in this programme and instead received usual care (study participants were not randomised). They found that women enrolled in this programme had lower rates of preterm birth, pre-eclampsia, growth restriction, NICU admission and neonatal morbidity. Programme participants delivered on average eight days later with birthweights on average 220 g (8 oz) larger.
Similar results were seen in the Higgins Nutritional Intervention Program in Montreal, which had similar recommendations as the Michigan Multiples Clinic.7 In their study, which was also not randomised, they found that participants had a significantly reduced risk of preterm birth and low birthweights.
The Issues (What We Do Not Know and Problems)
Even if we accept that for women with twin pregnancies, improved weight gain is associated with improved outcomes, several important questions remain:
• Do attempts to achieve these weight gain goals lead to improved outcomes? This is really two different questions. First, do these attempts even lead to the desired weight gain? Second, would the desired weight gain lead to the improved outcomes? At this time, neither is certain, but most experts (including this author) believe both are true. It is possible to improve nutrition and weight gain in most women with twins, and it likely would lead to improved outcomes.
• What is the ideal diet for women with twin pregnancies? Although many scholars have put forth recommendations, there are no high-quality studies to guide recommendations for caloric intake, nutrient composition and micronutrient requirements.
• Are there times in pregnancy when nutrition or weight gain has the greatest impact, and might those times differ for different outcomes such as preterm birth and fetal growth?
• What is the impact of ‘excessive’ weight gain in twin pregnancies? Is there a point when weight gain becomes detrimental?
Management Options
In our practice, for women with twin pregnancies, we recommend the following:
1. We review the current weight gain guidelines for twin pregnancies. It is usually easier to present them in average weight gain per week rather than over the entire pregnancy.
• BMI 18.6-24.9 kg/m2 (normal weight): 1.0 lb per week.
• BMI 25.0-29.9 kg/m2 (overweight): 0.75-1.0 lb per week.
• BMI 30.0 kg/m2 or higher (obese): 0.5-0.75 lb per week.
For women with an underweight pre-pregnancy BMI (< 18.6 kg/m2), we recommend the same weight gain as for women with a normal pre-pregnancy BMI. We base this on the results of a study we published examining outcomes in underweight women with twin pregnancies.8 In this study, we found that underweight women with twin pregnancies who achieve similar weight gain to normal-weight women with twin pregnancies had similar outcomes.
Therefore, we do not recommend a higher weight gain for underweight women with twin pregnancies.2. We recommend formal nutritional counselling for all women with twin pregnancies. We do this for several reasons. First, nutritional counselling takes time, and if it had to be covered thoroughly in a prenatal visit, it likely would either not be given enough attention or it would reduce the time needed for other important counselling. Second, it imparts on the patient the significance of this aspect of prenatal care. Third, the studies that showed improved outcomes with formal twin programmes all included dedicated nutritional counselling sessions.6,7 Finally, not all prenatal providers have the expertise to help women with their nutritional concerns, especially those with specialised diets (plant-based, gluten-free, certain allergies etc.) or difficulty consuming food due to nausea or early satiety, both of which are common in twin pregnancies.
3. For women with twin pregnancies whose weight gain exceeds the recommended weight gain, as long as they are maintaining a healthy diet and remaining active, we do not attempt to modify their diet to reduce weight gain.
4. Regarding micronutrient consumption, if a woman is taking a prenatal vitamin and has a well-balanced diet, we only recommend supplementation with calcium (to achieve 1,000-2,000 mg daily). We only recommend supplemental iron if she is anaemic. Since our patients all have formal nutritional counselling, we try to have women receive their other micronutrients by eating a well-balanced diet. If they are unable to do so, we recommend supplementation as needed. We do not routinely measure serum vitamin levels in women with twin pregnancies.
Activity and Exercise
The Facts (What We Know)
Recommendations regarding activity in women with twin pregnancies are often restrictive and not based on high-quality studies. A Cochrane review found no benefit to routine hospitalisation or bed rest in women with twin pregnancies.9 In routine pregnancies, women should try to achieve on average 20-30 minutes of moderate-intensity exercise four or five times a week.10
The Issues (What We Do Not Know and Problems)
Since women with twin pregnancies are at increased risk of preterm birth, it is unclear if regular exercise is beneficial, harmful or neither. It is also unclear if activity recommendations for women with twin pregnancies can and should be individualised based on history, symptoms, cervical length or other variables.
Management Options
In our practice, for women with twin pregnancies, we recommend the following regarding activity in pregnancy.
1. We do not routinely recommend bedrest.
2. We do not routinely recommend stopping working. However, we discuss the high likelihood that working full time will become more difficult as pregnancy progresses. Each woman will have to individualise her work schedule based on her specific job requirements, commute, and symptoms.
3. We do not place restrictions or limitations on sexual activity, aside from the typical restrictions for women with a singleton pregnancy, such as placenta praevia after 20 weeks, vaginal bleeding, preterm labor or ruptured membranes.
4. We recommend exercise similar to women with singleton pregnancies: an average of 20-30 minutes of moderate-intensity exercise 4-5 times a week. As with singleton pregnancies, the exact exercise, intensity, and amount of time will vary based on her prepregnancy exercise habits, her overall health status, and how far along she is in pregnancy. Women with twin pregnancies often have to modify their routines due to increasing uterine size and increasing fatigue.
5. For women with twin pregnancies and other factors concerning for preterm birth, such as contractions or a short cervical length, we do recommend modifying activities. There is no exact definition for ‘modify’ and it will likely differ for each woman. A good working definition would be a level of activity greater than complete bedrest, but less than whatever level brings about symptoms such as pressure or contractions. For some women that is very light activity, for other women it might allow for somewhat increased activity.
Travel
The Facts (What We Know)
Airline travel is considered safe in pregnancy, but since all pregnant women are at increased risk of thrombosis, and twin pregnancies especially so, it is probably prudent for women with twin pregnancies to take precautions to lower their risk of thrombosis, including compression stockings or periodic walking. Cosmic radiation is below the threshold level for fetal concerns. Women with twin pregnancies may go through security metal detectors as well. The radiation exposure from the newer backscatter units is 5 microrem, which is 1/ 600 the amount of cosmic radiation from the flight itself (3 milirem).
In regard to the travel destination, pregnant women should be aware of the potential infection exposures as well as the available medical care at each individual destination. Also, as pregnancy progresses, the risk of several pregnancy complications increases. Therefore, while there is no exact gestational age after which women cannot travel, each pregnant woman must balance the benefit of the trip with the potential risk of a complication at her destination.
The Issues (What We Do Not Know and Problems)
Since women with twin pregnancies are at increased risk of complications such as preterm birth and hypertension, it is unknown when exactly they should stop travelling, and whether this should be individualised based on history, symptoms, cervical length or other factors.
Management Options
In our practice, for women with twin pregnancies, we recommend the following in regards to travel:
1. In general, airline travel is safe in pregnancy.
2. Women with twin pregnancies should take extra precautions to prevent thrombosis, including frequent ambulation during awake hours on the plane. Since we recommend low-dose aspirin (81 mg) to all women with twin pregnancies, this might be preventative as well.
3. There is no exact gestational age below which women with twin pregnancies can be guaranteed that travel will be uncomplicated. Therefore, we advise women with twin pregnancies never to travel to areas without access to good medical care. When travelling to areas with access to good medical care, each woman must decide for herself the benefit of the travel versus the potential for a complication at that destination and how stressful or inconvenient that would be for her. In general, in an uncomplicated twin pregnancy, most women will travel within the United States and to developed countries until 28-32 weeks. After this time, usually they will not travel or will only go for short trips of great importance to them. Women with bleeding, a short cervix, preterm labour or other significant risk factors for preterm birth usually do not travel at all.
Key Points
• Women with twin pregnancies are at increased risk of pregnancy complications.
• There are very few high-quality studies to direct recommendations for lifestyle modifications in women with twin pregnancies.
• Improved nutrition and proper weight gain might be beneficial to women with twin pregnancies.
• In the absence of complications, most women with twin pregnancies can exercise regularly, continue working and have no restrictions in sexual activity.
• Most women with twin pregnancies can travel up to 28-32 weeks, provided they have access to medical care, do not have other significant complications and accept the small possibility of a complication at their destination.
References
1. Fox NS, Rebarber A, Roman AS, Klauser CK, Peress D, Saltzman DS. Weight gain in twin pregnancies and adverse outcomes: examining the 2009 Institute of Medicine guidelines. Obstet Gynecol 2010;116:100-6.
2. Fox NS, Saltzman DH, Kurtz H, Rebarber A. Excessive weight gain in term twin pregnancies: examining the 2009 Institute of Medicine definitions. Obstet Gynecol 2011 Nov;118(5):1000-4.
3. Liu LY, Zafman KB, Fox NS. Weight gain and pregnancy outcomes in overweight or obese women with twin gestations. J Matern Neonat Fetal Med 2019 [in press].
4. Fox NS, Stern E, Saltzman DH, Klauser CK, Gupta S, Rebarber A. The association between maternal weight gain and spontaneous preterm birth in twin pregnancies. J Matern Fetal Neonatal Med 2014;27(16):1652-5.
5. Liu LY, Zafman KB, Fox NS. The association between gestational weight gain in each trimester and pregnancy outcomes in twin pregnancies. Am J Perinatol 2019 [in press]
6. Luke B, Brown MB, Misiunas R et al. Specialized prenatal care and maternal and infant outcomes in twin pregnancy. Am
J Obstet Gynecol 2003 Oct;189(4):934-8.
7. Dubois S, Dougherty C, Duquette MP, Hanley JA, Moutquin JM. Twin pregnancy: the impact of the Higgins Nutritional Intervention Program on maternal and neonatal outcomes. Am J Clin Nutr 1991 Jun;53(6):1397-1403.
8. Liu L, Zafman KB, Fox NS. Weight gain and pregnancy outcomes in underweight women with twin pregnancies. J Matern Neonat Fetal Med 2018 [in press].
9. Crowther CA, Han S. Hospitalisation and bedrest for multiple pregnancy. Cochrane Database Syst Rev. 2010 Jul 7;(7): CD000110. https://doi.org/10.1002/146518 58.CD000110.pub2
10. American College of Obstetricians and Gynecologists. Physical activity and exercise during pregnancy and the postpartum period. Committee Opinion No. 650. Obstet Gynecol 2015;126:e135- e142.