# Establishing Optimal Gestational Weight Gain in Twin Pregnancies With a Prerequisite Rationale-A Tour de Force

Pierre-Yves Robillard

► To cite this version:

Pierre-Yves Robillard. Establishing Optimal Gestational Weight Gain in Twin Pregnancies With a Prerequisite Rationale-A Tour de Force. JAMA Network Open, 2022, 5 (7), 10.1001/jamanet-workopen.2022.22546. [https://doi.org/10.1001/jamanet-workopen.2022.22546](https://doi.org/10.1001/jamanet-workopen.2022.22546). This content may be used under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the work is properly cited.

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**Invited Commentary** | Obstetrics and Gynecology

# Establishing Optimal Gestational Weight Gain in Twin Pregnancies With a Prerequisite Rationale—A Tour de Force

Pierre-Yves Robillard, MD

Using a large US nationwide database of 200 000 twin pregnancies, Lin and colleagues¹ dared to confront a difficult problem: twin pregnancies. Analyses of twin pregnancies are a challenge for perinatal epidemiologists, such as me, owing to, for example, an individual with 2 infants, chorionicity, different sexes in a pair, and discordant birth weights as well as numerous potential traps. In addition, the "physiological normal term" for twins is approximately 36 weeks, with few reaching 39 weeks (in our experience, 2% for monozygotic twins and 3% for dizygotic twins). Given these conditions, what are good recommendations for optimal "term" gestational weight gain (GWG) in twin pregnancies?

Lin and colleagues¹ have bypassed many of these potential difficulties first by considering a standardized GWG at 36 weeks' gestation (after calculating GWG per week) to offer plausible and strong results. In addition, the low-risk group they selected (n = 61 794) is of great interest and had good exclusion criteria, namely, including only twins with appropriate growth for their gestational age (similar birth weights for both twins) and excluding pregnancies with lower than 36 weeks' gestation.

During the data analyses that considered several risk factors (small for gestational age [SGA] status, large for gestational age [LGA] status, hypertensive disorders of pregnancy, preterm birth <36 weeks' gestation) and a composite outcome, the authors discovered an unexpected phenomenon (the cornerstone of their work is shown in their Figure 4). The 10% crossing points of the SGA and LGA curves at 10% for the incidence of the composite outcome and individual morbidities by GWG groups and body mass index (BMI, calculated as weight in kilograms divided by height in meters squared) categories (underweight, normal, overweight, class 1 obesity, class 2 obesity, and class 3 obesity) were different based on the maternal prepregnancy BMI at the corresponding maternal GWG. The authors' second surprise was noticing that these differences were so regular that they could be described by a linear curve (with the equation y = mx + b).

I had a similar surprise in 2017 when studying GWG per maternal prepregnancy BMI category in singleton pregnancies on Reunion Island.² Considering the 10% crossing points of the SGA and LGA curves combined with the corresponding maternal prepregnancy BMIs, we proposed then to call these crossing points associated with specific maternal BMI the *Maternal Fetal Corpulence Symbiosis*.

The equation for optimal GWG (in kg) in singleton pregnancies identified in our previous study² was (-1.2 × prepregnancy BMI) + 42 ± 2 kg; and the equation for optimal GWG (in kg) in twin pregnancies identified by Lin et al¹ was (-0.932 × prepregnancy BMI) + 41.5 ± 2 kg. These equations describe 2 nearly parallel curves, with a GWG difference of approximately 7 kg between singletons and twins for each prepregnancy BMI. Applying these equations indicates that for a prepregnancy BMI of 20, optimal GWG for singletons is 18 kg and for twins is 24.7 kg; for a prepregnancy BMI of 25, optimal GWG for singletons is 12 kg and for twins is 18.2 kg; for a prepregnancy BMI of 30, optimal GWG for singletons is 6 kg and for twins is 13.5 kg; and for a prepregnancy BMI of 35, optimal GWG for singletons is 0 kg and for twins is 8 kg.

Regarding gestational hypertensive disorders, including preeclampsia, Figure 2 of the article by Lin et al¹ shows that the lowest incidence of these disorders was similar to the corresponding Maternal Fetal Corpulence Symbiosis in each category of BMI. We recently showed that applying the formula for singleton pregnancies to our population has the potential to lower by 40% the incidence

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Author affiliations and article information are listed at the end of this article.

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**Open Access.** This is an open access article distributed under the terms of the CC-BY License.
of late-onset preeclampsia,³ as increasing prepregnancy BMIs have a linear association with the incidence of late-onset preeclampsia⁴ and other important morbidities (eg, cesarean delivery, LGA, and newborns with macrosomia >4 kg)⁵ for individuals with overweight or obesity.

If the international community decided to adopt as a prerequisite rationale for optimal GWG to achieve a normal-shaped neonatal population curve (size appropriate for gestational age) at all gestational ages, the solution would be scientifically (and mathematically) achievable immediately. Because this optimal GWG is based on the outcomes of neonatal birth weights (SGA and LGA definitions differ across ethnic populations), every geographical area in the world could define its specific linear curve adapted to their population. Calculators could be created for the specific curves so that they are accessible to everyone with a smartphone, as has been the case for singleton pregnancies on Reunion Island for 3 years to date.⁶ Thus, at the first prenatal visit, every pregnant individual would know the personal GWG goal to achieve in the next 7 to 8 months of pregnancy.

The availability of the final GWG objective since the first prenatal visit (a kind of deal between the mother and the health worker), would make it easy to check every month from the 22nd week of gestation onward that the fetus is not SGA (and in this case, the initial GWG recommendation could be increased). Such a monthly follow-up on a population scale has the theoretical potential to lower the incidence of SGA status, excluding pathological conditions such as preeclampsia, from 10% to between 5% and 7% in all populations (taking into account differences in the SGA and LGA definitions among ethnic groups). This important leap forward would have immediate practical issues given that there are approximately 140 million births per year worldwide, of which approximately 1.7 million are twin pregnancies.

## ARTICLE INFORMATION

**Published:** July 19, 2022. doi:10.1001/jamanetworkopen.2022.22546

**Open Access:** This is an open access article distributed under the terms of the CC-BY License. © 2022 Robillard PY. JAMA Network Open.

**Corresponding Author:** Pierre-Yves Robillard, MD, Centre d'Etudes Périnatales Océan Indien (CEPOI), Centre Hospitalier Universitaire Sud Réunion, BP 350, Saint-Pierre 97448, Réunion, France (pierre-yves.roillard@chutherunion.fr).

**Author Affiliations:** Service de Néonatologie, Centre Hospitalier Universitaire Sud Réunion, Saint-Pierre, Réunion, France; Centre d'Etudes Périnatales Océan Indien (CEPOI), Centre Hospitalier Universitaire Sud Réunion, Saint-Pierre, Réunion, France.

**Conflict of Interest Disclosures:** None reported.

## REFERENCES

1. Lin D, Huang X, Fan D, et al. Association of optimal gestational weight gain ranges with perinatal outcomes across body mass index categories in twin pregnancies. JAMA Netw Open. 2022;5(7):e2222537. doi:10.1001/jamanetworkopen.2022.22537

2. Robillard PY, Dekker G, Boukerrou M, Le Moullec N, Hulsey TC. Relationship between pre-pregnancy maternal BMI and optimal weight gain in singleton pregnancies. Heliyon. 2018;4(5):e00615. doi:10.1016/j.heliyon.2018.e00615

3. Robillard PY, Dekker G, Boukerrou M, Boumahni B, Hulsey T, Scioscia M. Gestational weight gain and rate of late-onset preeclampsia: a retrospective analysis on 57 000 singleton pregnancies in Reunion Island. BMJ Open. 2020;10(7):e036549. doi:10.1136/bmjopen-2019-036549

4. Robillard PY, Dekker G, Scioscia M, et al. Increased BMI has a linear association with late-onset preeclampsia: a population-based study. PLoS One. 2019;14(10):e0223888. doi:10.1371/journal.pone.0223888

5. Robillard PY, Dekker GA, Boukerrou M, Boumahni B, Hulsey TC, Scioscia M. The urgent need to optimize gestational weight gain in overweight/obese women to lower maternal-fetal morbidities: a retrospective analysis on 59,000 singleton term pregnancies. Arch Women Health Care. 2020;3(3):1-9.

6. Réseau Périnatal Réunion (Repère). Gestational weight gain calculator (English version) on smartphone. Published September 2018. Accessed June 7, 2022. https://repere.re/weight-gain-during-my-pregnancy

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