Effect of maternal height and weight on risk of preterm birth in singleton and twin births resulting from in vitro fertilization: a retrospective cohort study using the Society for Assisted Reproductive Technology Clinic Outcome Reporting System

Higher risk of preterm twin delivery among shorter nulliparous women

OBJECTIVE

To determine if maternal height in nulliparous women influences pregnancy results in twin pregnancies.

MATERIAL AND METHODS

Retrospective cohort analysis evaluating twin pregnancies followed at Centro Hospitalar Universitário Lisboa Central, between 1995 and 2020. Of the 2900 pregnancies followed in that period, 886 nulliparous women with dichorionic twin pregnancies were selected. Two groups were considered: A - maternal height <163 cm (

RESULT(S)

PTB rates decreased along increasing maternal height. The comparison between group A and group B revealed no statistically significant differences in maternal characteristics (age, mode of conception - spontaneous or ART pregnancies, or BMI). Statistically significant differences were found in mean gestational age at birth (35.1 ± 1.8 vs. 36.0 ± 2.6 wks), PTB rates < 32, 34 and 36 wks, OR: 3.2, 2.3 and 2.4 respectively, p < 0.01. Shorter women had a 1.7× and 2.6× increased risk for significantly low (<2500 g) and very low (<1500 g) newborn birth weight (BW), respectively, and a 40 % increased risk of Cesarian delivery. No significant differences were shown with respect to stillbirths, neonatal and perinatal deaths, which had a low incidence in this study. In ART pregnancies we found the same results regarding PTB rates and newborn birthweight in shorter women. In Logistic Regression analysis, maternal height

CONCLUSION

Increased pregnancy risk in nulliparous shorter women should be taken into consideration in double embryo transfers.

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Key Words

• Art
• Dichorionic twins
• Maternal height
• Nulliparous women
• Perinatal outcomes

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MESH Headings

• Pregnancy
• Infant, Newborn
• Female
• Humans
• Infant
• Pregnancy, Twin
• Stillbirth
• Retrospective Studies
• Cesarean Section/adverse effects
• Premature Birth/epidemiology
• Infant, Very Low Birth Weight
• Birth Weight

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Affiliation(s)

Teresinha Simões Department of Maternal-Fetal Medicine, Maternity Dr. Alfredo da Costa, Centro Hospitalar Lisboa Central and Nova Medical School, Lisbon, Portugal; Department of Reproductive Medicine, Maternity Dr. Alfredo da Costa, Centro Hospitalar Lisboa Central and Nova Medical School, Lisbon, Portugal.
Inês Pereira Department of Maternal-Fetal Medicine, Maternity Dr. Alfredo da Costa, Centro Hospitalar Lisboa Central, Lisbon, Portugal
Laura Gomes Department of Maternal-Fetal Medicine, Maternity Dr. Alfredo da Costa, Centro Hospitalar Lisboa Central, Lisbon, Portugal
Sofia Brás Department of Maternal-Fetal Medicine, Maternity Dr. Alfredo da Costa, Centro Hospitalar Lisboa Central, Lisbon, Portugal
Isabel Nogueira Department of Maternal-Fetal Medicine, Maternity Dr. Alfredo da Costa, Centro Hospitalar Lisboa Central, Lisbon, Portugal
Alexandra Queirós Department of Maternal-Fetal Medicine, Prenatal Diagnosis Unit Maternity Dr. Alfredo da Costa, Centro Hospitalar Lisboa Central and Nova Medical School, Lisbon, Portugal

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Association between pre-pregnancy BMI and neonatal weight outcomes in twin pregnancies resulting from assisted reproductive technology: a 10-year cohort study

BACKGROUND/OBJECTIVES

To examine the effect of pre-pregnancy maternal body mass index (BMI) on neonatal weight outcomes of twin infants who were conceived by assisted reproductive technology (ART).

SUBJECTS/METHODS

A 10-year (2006-2015) Chinese sample of 3431 mothers and their twin infants conceived by ART from a retrospective cohort were included. The effects of pre-pregnancy maternal BMI on gestational age and birth weight were assessed by generalized linear model and generalized estimating equation model.

RESULTS

Compared with a normal weight group, pre-pregnancy maternal underweight was associated with lower birth weight and increased risk of small for gestational age (SGA) in twins conceived by ART (birth weight: difference -59.22 g, 95% CI -93.16 to -25.27 g; SGA: RR 1.25, 95% CI 1.09 to 1.43). Pre-pregnancy maternal obesity was associated with higher birth weight and increased risk of preterm birth (birth weight: difference 65.82 g, 95% CI 10.66 to 120.99 g; preterm birth: RR 1.19, 95% CI 1.03-1.37). A nonlinear relationship between pre-pregnancy maternal BMI and SGA was observed. The risk of SGA decreased with the pre-pregnancy maternal BMI up to the turning point (BMI = 21) (RR 0.90, 95% CI 0.86-0.95).

CONCLUSIONS

Among mothers undergoing ART, pre-pregnancy maternal obesity is associated with higher birth weight and higher risk of preterm birth for twin pregnancy, and pre-pregnancy maternal underweight is associated with lower birth weight and higher risk of SGA. Women preparing for ART should maintain a normal BMI to lower the chances of adverse neonatal outcomes.

Effect of pre-pregnancy body mass index on neonatal outcomes in women undergoing autologous frozen-thawed embryo transfer

OBJECTIVE

To investigate the associations between pre-pregnancy body mass index (BMI) and neonatal outcomes in women undergoing autologous frozen-thawed embryo transfer (FET).

DESIGN

Retrospective cohort study.

SETTING(S)

University-affiliated reproductive medical center.

PATIENT(S)

A total of 16,240 women with singleton deliveries achieved by autologous FET.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Neonatal outcomes included preterm birth (PTB), low birth weight (LBW), small-for-gestational age (SGA), large-for-gestational age (LGA), fetal macrosomia, and birth defects.

RESULT(S)

After adjusting for confounding factors, our study showed that in autologous FET cycles, the overweight women (23 kg/m²≤ BMI <27.5 kg/m²) were associated with increased rates of PTB (adjusted odds ratio [aOR], 1.226; 95% confidence interval [CI], 1.060-1.418), macrosomia (aOR, 1.692; 95% CI, 1.491-1.921), and LGA (aOR, 1.980; 95% CI, 1.715-2.286); and the obese women (BMI ≥27.5 kg/m²) were significantly associated with increased PTB (aOR, 1.503; 95% CI, 1.167-1.936), early PTB (aOR, 2.829; 95% CI, 1.679-4.765), very LBW (aOR, 3.087; 95% CI, 1.720-5.542), macrosomia (aOR, 2.325; 95% CI, 1.862-2.904), and LGA (aOR, 3.235; 95% CI, 2.561-4.085). The rate of SGA infants was higher in the underweight women (BMI <18.5 kg/m²) (aOR, 1.687; 95% CI, 1.375-2.071) than that in the normal-weight women (18.5 kg/m²≤ BMI ≤23 kg/m²). No significant difference was observed in the risk of birth defects between normal-weight cases and other BMI categories.

CONCLUSION(S)

Among women undergoing FET, pre-pregnancy BMI affected neonatal outcomes of singletons. BMI in Asian categories for overweight and obese showed significant increases in PTB, macrosomia, and LGA; early PTB and very LBW only increased in obese cases. In addition, underweight status was associated with increased risk of SGA. In contrast, there was no association between pre-pregnancy BMI and birth defects in FET cycles.

Perinatal Outcomes and Risk Factors for Preterm Birth in Twin Pregnancies in a Chinese Population: A Multi-center Retrospective Study

Background: Twin pregnancies are associated with an increased risk of adverse maternal and neonatal outcomes, mainly owing to prematurity. Few studies have evaluated the risk factors for preterm birth (PTB) in Chinese population. The objective of this study is to present the short-term maternal-neonatal outcomes, investigating the potential risk factors associated with preterm birth in Chinese twin pregnancies.

Methods: A multi-center retrospective study of women pregnant with twins ≥28 weeks of gestation was conducted. Maternal and neonatal outcomes were analyzed. Logistic regression was used to identify potential risk factors for PTB before 37, 34, and 32 weeks, respectively.

Results: A total of 3,288 twin pregnancies and 6,576 neonates were included in 99,585 pregnancies. The rate of twin pregnancy was 3.3%, while the PTB rate before 37, 34, and 32 weeks among this population were 62.1, 18.8, and 10.4%, respectively. Logistic regression revealed that monochorionicity [Odds ratio (OR) 3.028, 95% confident interval (CI) 2.489–3.683, P < 0.001], gestational weight gain (GWG) <10 kg (OR 2.285, 95% CI 1.563–3.339, P < 0.001) and GWG between 10 and 15 kg (OR 1.478, 95% CI 1.188–1.839, P < 0.001), preeclampsia (PE) (OR 3.067, 95% CI 2.142–4.390, P < 0.001), and intrahepatic cholestasis of pregnancy (ICP) (OR 3.122, 95% CI 2.121–4.596, P < 0.001) were the risk factors for PTB before 37 weeks. Monochorionicity (OR 2.865, 95% CI 2.344–3.501, P < 0.001), age < 25 years (OR 1.888, 95% CI 1.307–2.728, P = 0.001), and GWG <10 kg (OR 3.100, 95% CI 2.198–4.372, P < 0.001) were risk factors for PTB before 34 weeks. Monochorionicity (OR 2.566, 95% CI 1.991–3.307, P < 0.001), age younger than 25 years (OR 1.964, 95% CI 1.265–3.048, P = 0.003), and GWG <10 kg (OR 4.319, 95% CI 2.931–6.364, P < 0.001) were the risk factors for PTB before 32 weeks.

Conclusions: Monochorionicity and GWG <10 kg were two major risk factors for PTB before 32, 34, and 37 weeks, whereas maternal age, PE, and ICP were also risk factors for PTB in specific gestational age.

Adverse effects of pre-pregnancy maternal underweight on pregnancy and perinatal outcomes in a freeze-all policy

BACKGROUND

Underweight and overweight may affect reproduction and interfere with treatment of infertility. In the present retrospective analysis, we sought to evaluate the effect of low body mass index (BMI) on pregnancy and perinatal outcomes in frozen-thawed embryo transfer (FET) cycles.

METHODS

This study involved 8755 FET cycles in a single IVF center during the period from January 2009 to December 2018. Both pregnancy and perinatal outcomes were assessed in women who were underweight, normal weight, and overweight as defined based on a respective BMI < 18.5 kg/m², ≥ 18.5 BMI < 24.9 kg/m², and BMI ≥ 25 kg/m².

RESULTS

Being underweight was linked to reduced implantation rates as compared to a normal weight (33.56% vs. 37.26%). Similarly, when comparing outcomes in underweight women to those in normal weight women, rates of clinical pregnancy (48.14% vs. 53.85%) and ongoing pregnancy (43.04% vs. 50.47%) were reduced. Rates of miscarriage were markedly reduced in the normal weight group relative to the overweight group (10.73% vs. 13.37%). Perinatal outcomes were largely comparable for all groups, with the exception of very low birth weight rates (normal weight:0.58% vs. overweight: 2.03%), very small for gestational age rates (normal weight:1.31% vs. overweight:3.55%) and very preterm delivery rates (normal weight:0.82% vs. overweight: 2.03%), which were significantly elevated for overweight mothers.

CONCLUSIONS

These results indicate that being underweight is linked to negative pregnancy outcomes when undergoing FET-based IVF.

Effects of a high-fat diet on the lipid profile of oocytes in mice

Существуют предпосылки того, что у женщин с ожирением возможно снижение качества ооцитов. При этом остается неясным, как связано это изменение с ожирением: опосредованно или напрямую, че- рез изменение содержания и/или состава липидов в ооцитах. Целью настоящей работы было изучение на мышах влияния богатой жирами диеты, применяемой к самкам-донорам, на качественный состав и общее количество липидов в незрелых и созревших in vivo ооцитах. Установлено, что диета, богатая липидами, при- водит к увеличению массы тела самок мышей по сравнению с контролем ( p < 0.001; 44.77 ± 1.46 и 35.22 ± 1.57 соответственно), а также уровня холестерина ( p < 0.05; 2.06 ± 0.10 и 1.78 ± 0.10 соответственно) и триглицери- дов ( p < 0.05; 2.13 ± 0.23 и 1.49 ± 0.21 соответственно) в крови этих животных. Эта диета не повлияла на степень ненасыщенности внутриклеточных липидов незрелых (0.207 ± 0.004 в эксперименте и 0.206 ± 0.002 в контроле) и зрелых ооцитов (0.212 ± 0.005 в эксперименте и 0.211 ± 0.003 в контроле). При созревании ооцитов in vivo на- блюдалось возрастание содержания внутриклеточных липидов. В зрелых ооцитах количество липидов было больше в экспериментальной группе по сравнению с контролем ( p < 0.01; 8.15 ± 0.37 и 5.83 ± 0.14 соответствен- но). Выявлено увеличение количества внутриклеточных липидов при созревании ооцитов как после стан- дартной диеты ( p < 0.05; 4.72 ± 0.48 и 5.83 ± 0.14 соответственно), так и после диеты, богатой жирами ( p < 0.001; 3.45 ± 0.62 и 8.15 ± 0.37 соответственно). Таким образом, при созревании ооцитов мышей in vivo возрастает со- держание внутриклеточных липидов, богатая жирами диета приводит к повышенному содержанию липидов в зрелых ооцитах.

Challenges for better care based on the course of maternal body mass index, weight gain and multiple outcome in twin pregnancies: a population-based retrospective cohort study in Hessen/Germany within 15 years

Introduction

Studies on maternal weight, gestational weight gain and associated outcomes in twin pregnancies are scarce. Therefore, we analyzed these items in a large cohort.

Methods

Data from 10,603/13,725 total twin pregnancies from the perinatal database in Hessen, Germany between 2000 and 2015 were used after exclusion of incomplete or non-plausible data sets. The course of maternal and perinatal outcomes was evaluated by linear and logistic regression models.

Results

The rate of twin pregnancies increased from 1.5 to 1.9% (p < 0.00001). Mean maternal age and pre-pregnancy weight rose from 31.4 to 32.9 years and from 68.2 to 71.2 kg, respectively (p < 0.001). The rates of women with a body mass index ≥ 30 kg/m² increased from 11.9 to 16.9% with a mean of 24.4–25.4 kg/m² (p < 0.001). The overall increase of maternal weight/week was 568 g, the 25th quartile was 419, the 75th quartile 692 g/week. The total and secondary caesareans increased from 68.6 to 73.3% and from 20.6 to 39.8%, respectively (p < 0.001). Rates of birthweight < 1500 g and of preterm birth < 28 and from 28 to 33 + 6 weeks all increased (p < 0.01). No significant changes were observed in the rates of stillbirth, perinatal mortality and NICU admissions.

Conclusion

The global trend of the obesity epidemic is equally observed in German twin pregnancies. The increase of mean maternal weight and the calculated quartiles specific for twin pregnancies help to identify inadequate weight gain in twin gestations. Policy makers should be aware of future health risks specified for singleton and twin gestations.

Effect of maternal body mass index on neonatal outcomes in women with endometriosis undergoing IVF

RESEARCH QUESTION

Does preconception body mass index (BMI) affect neonatal outcomes in women with endometriosis who conceive with IVF?

DESIGN

This retrospective study included 7086 women who delivered a singleton live birth through IVF between December 2006 and December 2017. Of these, 1111 women were diagnosed with endometriosis by laparoscopy or laparotomy, while 5975 women received IVF treatment due to tubal factor or male factor infertility. Women were categorized according to predefined BMI groups (<18.5 kg/m², BMI 18.5-24.9 kg/m², ≥25 kg/m²). All comparisons performed were between women undergoing cryopreserved embryo transfer.

RESULTS

After stratification by BMI, underweight women with endometriosis showed higher preterm birth (PTB) rates compared with controls (14.61% versus 3.28%, P < 0.001), whereas normal weight and overweight/obese endometriotic women had similar PTB rates to controls. There was a significant interactive effect of endometriosis and maternal BMI on preterm delivery (P for interaction <0.05). After adjustment for potential confounding factors, the PTB rate remained consistently higher in the low BMI subgroup of women with endometriosis (adjusted odds ratio 4.66, 95% confidence interval 2.54-8.57), whereas this difference was not observed for the other BMI categories. Additionally, we noted no differences in the rate of early PTB, low birthweight, macrosomia, small for gestational age and large for gestational age between women with endometriosis and controls with respect to any preconception category of BMI.

CONCLUSIONS

Endometriotic patients who were underweight before conception (BMI <18.5 kg/m²) had a higher rate of PTB than women without endometriosis, but the difference was not observed in the other BMI categories.

Effect of the Interaction Between Pre-pregnancy Body Mass Index and Fresh/Frozen Embryo Transfer on Perinatal Outcomes of Assisted Reproductive Technology-Conceived Singletons: A Retrospective Cohort Study

Objective: To demonstrate the association between pre-pregnancy maternal overweight, obesity, and perinatal outcomes of singletons conceived by assisted reproductive technology (ART). Design: Retrospective cohort study from 2006 to 2015 data from a single ART center. Setting: Assisted Reproduction Center, Northwest Women's and Children's Hospital, Xi'an, Northwestern China. Patients: We included 7,818 women undergoing ART and their singleton infants. Interventions: None. Main Outcome Measure: The primary outcome measures were preterm birth (PTB), macrosomia, low birth weight, small for gestational age, and large for gestational age (LGA). Results: We experienced an increase in the risk of PTB, macrosomia, and LGA in overweight and obese groups compared with that in normal-weight groups [PTB: overweight vs. normal weight: odds ratio [OR] = 1.44, 95% CI: 1.18-1.75; obesity vs. normal weight: OR = 1.53, 95% CI: 1.04-2.25; macrosomia: overweight vs. normal weight: OR = 1.78, 95% CI: 1.48-2.14; obesity vs. normal weight: OR = 2.16, 95% CI: 1.52-3.06; LGA: overweight vs. normal weight: OR = 1.63, 95% CI: 1.39-1.90; obesity vs. normal weight: OR = 2.11, 95% CI: 1.57-2.83]. We observed a significant interaction between maternal BMI and fresh/frozen embryo transfer on PTB and LGA (P = 0.030; P = 0.030). Fresh embryo transfer significantly increased the effect of maternal BMI on LGA (fresh: OR = 1.14, 95% CI: 1.10-1.18; frozen: OR = 1.09, 95% CI: 1.04-1.13), and frozen embryo transfer increased the effect of maternal BMI on PTB (fresh: OR = 1.03, 95% CI: 0.99-1.08; frozen: OR = 1.09, 95% CI: 1.04-1.15). Conclusions: Pre-pregnancy maternal overweight and obesity were associated with higher risks of PTB, macrosomia, and LGA in ART-conceived singletons. These associations were affected by the timing of embryo transfer (fresh/frozen embryo transfer). Therefore, we recommend women before ART to maintain a normal BMI for the prevention of adverse perinatal outcomes.

A propensity-matched study of the association between pre-pregnancy maternal underweight and perinatal outcomes of singletons conceived through assisted reproductive technology

RESEARCH QUESTION

Is pre-pregnancy maternal underweight associated with perinatal outcomes of singletons who were conceived through assisted reproductive technology (ART)?

DESIGN

A 10-year (2006-2015) Chinese sample of 6538 women and their singleton infants who were conceived through ART was used to examine the association between pre-pregnancy maternal underweight and perinatal outcomes. Propensity scores for underweight were calculated for each participant using multivariable logistic regression, which was used to match 740 (91.36% of 810) underweight women with 740 normal weight women; the effects of underweight on birth weight and gestational age were then assessed by generalized estimating equation model.

RESULTS

After propensity score matching, the birth weight was lower (difference -136.83 g, 95% CI -184.11 to -89.55 g) in the underweight group than in the normal weight group. The risks of low birth weight (LBW) and small for gestational age (SGA) were increased in the underweight group compared with those in the normal weight group (LBW: RR 1.64, 95% CI 1.01 to 2.67; SGA: RR 1.46, 95% CI 1.06 to 2.02). The risks of fetal macrosomia and being large for gestational age (LGA) were decreased in the underweight group compared with those in the normal weight group (macrosomia: RR 0.39, 95% CI 0.26 to 0.61; LGA: RR 0.36, 95% CI 0.24 to 0.53). The associations between underweight, gestational age and preterm birth were not statistically significant.

CONCLUSIONS

Among women undergoing ART, pre-pregnancy maternal underweight was associated with lower birth weight, increased LBW and SGA risks, and decreased fetal macrosomia and LGA risks in singleton infants.

Maternal characteristics of preterm singleton birth following assisted reproduction: a population-based study

OBJECTIVE

To identify pregestational maternal characteristics that are associated with an increased risk for preterm births (PTB) of assisted reproductive technology (ART) singleton pregnancies.

PATIENTS AND METHODS

We evaluated the Slovenian National Perinatal Information System (NPIS). We included all ART singletons born during the period 2006-2015. We compared births before and after 36 completed weeks' gestation for maternal age, parity, prepregnancy BMI, height, previous PTB, preexisting hypertension and diabetes, and history of uterine gynecological operations.

RESULTS

Chronic hypertension (OR 2.5, 95% CI 1.3-4.8), previous preterm birth (OR 2.4, 95% CI 1.5-3.7), pregravid obesity (OR 1.6, 95% CI 1.2-2.1) and an existing indication for cerclage (OR 6.2, 95% CI 3.7-10.5) were associated with an increased risk of PTB.

CONCLUSIONS

Chronic hypertension, previous PTB, pregravid obesity and an existing indication for cerclage are associated with increased risk of PTB among ART pregnancies.

Maternal clinical predictors of preterm birth in twin pregnancies: A systematic review involving 2,930,958 twin pregnancies

In twin pregnancies, which are at high risk of preterm birth, it is not known if maternal clinical characteristics pose additional risks. We undertook a systematic review to assess the risk of both spontaneous and iatrogenic early (<34 weeks) or late preterm birth (<37 weeks) in twin pregnancies based on maternal clinical predictors. We searched the electronic databases from January 1990 to November 2017 without language restrictions. We included studies on women with monochorionic or dichorionic twin pregnancies that evaluated clinical predictors and preterm births. We reported our findings as odds ratio (OR) with 95% confidence intervals (CI) and pooled the estimates using random-effects meta-analysis for various predictor thresholds. From 12, 473 citations, we included 59 studies (2,930,958 pregnancies). The risks of early preterm birth in twin pregnancies were significantly increased in women with a previous history of preterm birth (OR 2.67, 95% CI 2.16-3.29, I² = 0%), teenagers (OR 1.81, 95% CI 1.68-1.95, I² = 0%), BMI > 35 (OR 1.63, 95% CI 1.30-2.05, I² = 52%), nulliparous (OR 1.51, 95% CI 1.38-1.65, I² = 73%), non-white vs. white (OR 1.31, 95% CI 1.20-1.43, I² = 0%), black vs. non-black (OR 1.38, 95% CI 1.07-1.77, I² = 98%), diabetes (OR 1.73, 95% CI 1.29-2.33, I² = 0%) and smokers (OR 1.30, 95% CI 1.23-1.37, I² = 0%). The odds of late preterm birth were also increased in women with history of preterm birth (OR 3.08, 95% CI 2.10-4.51, I² = 73%), teenagers (OR 1.36, 95% CI 1.18-1.57, I² = 57%), BMI > 35 (OR 1.18, 95% CI 1.02-1.35, I² = 46%), nulliparous (OR 1.41, 95% CI 1.23-1.62, I² = 68%), diabetes (OR 1.44, 95% CI 1.05-1.98, I² = 55%) and hypertension (OR 1.49, CI 1.20-1.86, I² = 52%). The additional risks posed by maternal clinical characteristics for early and late preterm birth should be taken into account while counseling and managing women with twin pregnancies.

Extremities of body mass index and their association with pregnancy outcomes in women undergoing in vitro fertilization in the United States

OBJECTIVE

To investigate the associations among underweight body mass index (BMI), pregnancy, and obstetric outcomes among women using assisted reproductive technology (ART).

DESIGN

Retrospective cohort study using national data and log binomial regression.

SETTING

Not applicable.

PATIENT(S)

Women undergoing IVF in the United States from 2008 to 2013.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Pregnancy outcomes (intrauterine pregnancy, live birth rates) per transfer, miscarriage rate per pregnancy, and low birth weight and preterm delivery rates among singleton and twin pregnancies.

RESULT(S)

For all fresh autologous in vitro fertilization (IVF) cycles in the United States from 2008 to 2013 (n = 494,097 cycles, n = 402,742 transfers, n = 180,855 pregnancies) reported to the national ART Surveillance System, compared with normal weight women, underweight women had a statistically significant decreased chance of intrauterine pregnancy (adjusted risk ratio [aRR] 0.97; 95% confidence interval [CI], 0.96-0.99) and live birth (aRR 0.95; 95% CI, 0.93-0.98) per transfer. Obese women also had a statistically decreased likelihood of both (aRR 0.94; 95% CI, 0.94-0.95; aRR 0.87; 95% CI, 0.86-0.88, respectively). Among cycles resulting in singleton pregnancy, both underweight and obese statuses were associated with increased risk of low birth weight (aRR 1.39; 95% CI, 1.25-1.54, aRR 1.26; 95% CI, 1.20-1.33, respectively) and preterm delivery (aRR 1.12; 95% CI, 1.01-1.23, aRR 1.42; 95% CI, 1.36-1.48, respectively). The association between underweight status and miscarriage was not statistically significant (aRR 1.04; 95% CI, 0.98-1.11). In contrast, obesity was associated with a statistically significantly increased miscarriage risk (aRR 1.23; 95% CI, 1.20-1.26).

CONCLUSION(S)

Among women undergoing IVF, prepregnancy BMI affects pregnancy and obstetric outcomes. Underweight status may have a limited impact on pregnancy and live-birth rates, but it is associated with increased preterm and low-birth-weight delivery risk. Obesity negatively impacts all ART and obstetric outcomes investigated.

Maternal obesity in mice not only affects fresh embryo quality but also aggravates injury due to vitrification

PURPOSE

The aims of the present study are to identify the mechanism(s) whereby obesity impairs fresh embryos and to clarify the effects of vitrification on lipid droplet content within embryos from maternally obese mice.

METHODS

The diet-induced obesity mouse model was established, and the zygotes were captured and cultured to day 3. The eight-cell embryos were selected and divided into fresh and vitrified groups. The blastocysts derived from fresh embryos were used as a control. The expression profiles of endoplasmic reticulum (ER) stress genes (Atf4, Grp78, and Hsp70) and other genes (MnSOD, p53, Gadd45g, caspase-3, IGF-II, ZO-1, and E-cadherin) on day-3 fresh and post-warming eight-cell embryos from obese and control groups were determined. For day-5 fresh blastocysts and blastocysts previously vitrified on day 3, the expression profiles for all of the above genes were also determined.

RESULTS

For the fresh group, obesity significantly upregulated Hsp70, p53, IGF-II, and ZO-1 expression in embryos on day 3 and notably upregulated Atf4, MnSOD, Gadd45g, caspase-3, ZO-1, and E-cadherin expression in blastocysts on day 5. For vitrified ones, obesity significantly upregulated Atf4, MnSOD, and Gadd45g expression in embryos on day 3 and notably upregulated Hsp70 expression and downregulated MnSOD in day 5 blastocysts previously vitrified on day 3.

CONCLUSIONS

Obesity impairs fresh embryos and aggravates embryonic vitrification injury at a molecular level.

The association between maternal height and pregnancy outcomes in twin gestations

OBJECTIVE

We sought to assess the association between maternal height and the risk of preterm birth, fetal growth restriction and mode of delivery in twin gestations.

STUDY DESIGN

Cohort study of patients with twin pregnancies delivered from 2005 to 2014. We compared pregnancy outcomes between patients of short stature ≤159 cm to those of normal stature ≥160 cm. Patients with monoamniotic twins and major fetal anomalies were excluded. Pearson's correlation, Chi-square and Student's t-test were used as appropriate.

RESULTS

Six hundred and sixty-six patients were included, 159 (23.9%) of whom had short stature (mean height 155.8 ± 2.5 cm) and 507 (76.1%) of whom had normal stature (mean height 167.2 ± 5.5 cm). There were no differences in outcomes between the groups in regards to preterm birth, gestational age (GA) at delivery, birth weight of either twin, preeclampsia, gestational diabetes or cesarean section rate. Results were similar when the groups were stratified by parity. As a continuous variable, maternal height did not correlate with GA at delivery (p= 0.388), cesarean delivery (p = 0.522) nor the birth weight of the larger (p = 0.206) or smaller (p = 0.307) twin.

CONCLUSION

In twin pregnancies, maternal short stature is not associated with preterm birth, fetal growth restriction or cesarean section rate. This suggests that although anthropometric measurements have long been used to counsel patients in regards to outcomes, patients of short stature should be reassured that their height does not appear to lead to adverse twin pregnancy outcomes.

Aging and the environment affect gamete and embryo potential: can we intervene?

Optimal maturation of the oocyte depends on its environment and determines embryo competence, because the embryonic genome is not active until the cleavage stage and new mitochondria are not produced until blastulation. Adverse environmental factors include aging, andropause, oxidative stress, obesity, smoking, alcohol, and psychologic stress, whereas androgen supplementation, a prudent diet, exercise, nutritional supplements, and psychologic interventions have beneficial effects. Mitochondrial function and energy production deteriorate with age, adversely affecting ovarian reserve, chromosome segregation, and embryo competence. In aging mice, the mitochondrial cofactor coenzyme Q10 reverses most of these changes. Early human experience has been encouraging, although only a small study using a shorter duration of intervention compared with the murine model has been carried out. Mitochondrial metabolic stress can result in an abnormal compensatory increase in mitochondrial DNA, which can be assessed in biopsied blastomeres of trophectoderm as a predictive biomarker of implantation failure. Psychologic stress may reduce oocyte competence by shifting blood flow away from the ovary as part of the classic "fight or flight" physiologic response, and methods to reduce stress or the body's reaction to stress improve pregnancy success. Enhancing oocyte competence is a key intervention that promises to reduce the number of euploid embryos failing to produce viable deliveries.

DEFINING ELIGIBILITY CRITERIA FOR FUNDING POLICIES AROUND IN VITRO FERTILIZATION

Objectives: This review aims to assess the state of the science around the potential impact of certain patient characteristics on the safety and effectiveness of in vitro fertilization (IVF).

Methods: Following Cochrane Collaboration guidelines and the PRISMA statement, a comprehensive systematic review of reviews and recent primary studies examining the impact of paternal age and maternal age, smoking, and body mass index (BMI) on the safety and effectiveness of IVF was performed. Papers, published between January 2007 and June 2014, were independently reviewed and critically appraised by two researchers using published quality assessment tools for reviews and primary studies. Due to heterogeneity across papers (different study designs and patient selection criteria), a qualitative analysis of extracted information was performed.

Results: Seventeen papers (ten systematic reviews and seven primary studies) were included. They comprised evidence from retrospective observational studies in which maternal age, BMI, and smoking status were explored as part of secondary analyses of larger studies. The majority of papers found that the likelihood of achieving a pregnancy was lower among women who were >40 years, had a BMI ≥ 25 and smoked. Advanced maternal age and BMI were also associated with higher rates of preterm birth and low birth weight.

Conclusions: Based on available evidence, it may be appropriate to consider “maternal age” and “morbid obesity” in public funding policies that aim to maximize the effectiveness of IVF. However, given inconsistencies in the effect of smoking across different pregnancy-related outcomes, support for incorporating it into funding conditions appears weak.

Effect of maternal height and weight on risk for preterm singleton and twin births resulting from IVF in the United States, 2008-2010

OBJECTIVE

To analyze the effects of preconception maternal height and weight on the risk of preterm singleton and twin births resulting from in vitro fertilization (IVF).

STUDY DESIGN

We performed a retrospective cohort analysis of the incidence of very early preterm birth (VEPTB), early preterm birth (EPTB), and preterm birth (PTB), before 28, 32, and 37 completed weeks, respectively, in 60,232 singleton and 24,111 twin live births using 2008-2010 live birth outcome data from the Society for Reproductive Technology Clinic Outcome Reporting System.

RESULT

Maternal obesity is associated with significantly increased risk of VEPTB, EPTB, and PTB in pregnancies conceived by IVF. For morbidly obese women (body mass index ≥35) with singletons, rates of VEPTB, EPTB, and PTB were 1.7%, 3.6%, and 16.4%, with adjusted risk ratios (aRRs) and 95% confidence levels (CIs) of 2.6 (1.8-3.6), 2.2 (1.8-2.6), and 1.5 (1.4-1.7) using corresponding rates for normal body mass index (95% CI, 18.6-24.9) as referent. For morbidly obese women with twins, rate of VEPTB and EPTB were 6.5% and 12.5%, with aRRs and 95% CIs of 2.4 (1.8-3.0) and 1.5 (1.3-1.8). For singletons, the rate of PTB for short stature women (<150 cm) was 14.2%, as compared with 11.8% in those women with height ranging between 160-167 cm (referent), with aRRs and 95% CIs of 1.2 (1.0-1.4).

CONCLUSION

Preconception maternal obesity and short stature are associated with significantly increased risk of VEPTB and early preterm singleton and twin births in pregnancies resulting from IVF.

Increased risk of preterm birth in singleton pregnancies after blastocyst versus Day 3 embryo transfer: Canadian ART Register (CARTR) analysis

STUDY QUESTION

Are the fetal outcomes of singleton pregnancies that result from cleavage stage embryo transfer (ET) different from the outcomes from Day 5/6 blastocyst stage ET?

SUMMARY ANSWER

There was a significantly higher risk of preterm birth (<37 weeks) in singletons after extended embryo culture (Day 5/6) compared with cleavage stage (Day 3) transfer.

WHAT IS KNOWN ALREADY

Two recent studies, from Sweden and the USA, reported an increased risk of preterm birth in singleton pregnancies after Day 5/6 ET compared with Day 3 ET. The US study also showed increased early preterm births and the Swedish study showed increased fetal malformations in this group.

STUDY DESIGN, SIZE AND DURATION

A retrospective cohort study was performed. Data were collected from the Canadian ART Register database for all singleton births after fresh IVF/ICSI ET cycles (2001-2009).

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 12 712 singleton births were included. Of these, 9506 resulted from a Day 3 ET and 3206 resulted from a blastocyst (Day 5/6) ET.

MAIN RESULTS AND THE ROLE OF CHANCE

Preterm birth rate <37 weeks (unadjusted by potential confounding factors) was higher with Day 5/6 versus Day 3 transfers (17.2 versus 14.1%, P < 0.001). Using logistic regression analysis to adjust for confounding factors, preterm birth rate <37 weeks was the only outcome significantly increased after Day 5/6 compared with Day 3 transfer (odds ratio 1.32, 95% confidence interval 1.17-1.49). The following confounding factors were adjusted for: year of treatment (2001-2009), maternal age (continuous), parity (0 versus ≥1 birth), diagnosis category, number of oocytes retrieved [≤20 versus >20 (high responder group)], insemination method (IVF versus ICSI), number of embryos transferred (1, 2 or ≥3) and the presence of a vanishing twin (≥1 fetal heart on the initial ultrasonographic examination).

LIMITATIONS, REASONS FOR CAUTION

Post-natal follow-up studies will be required to determine if this difference we observed translates into adverse long-term effects on these offspring. The rate of early preterm births (<32 weeks) was higher in Day 5/6 versus Day 3, but the low number of cases in this category did not have the power to show a difference (3.0 versus 2.7%, P = 0.34).

WIDER IMPLICATIONS OF THE FINDINGS

We found a significantly higher risk of preterm birth (<37 weeks) in singletons after extended embryo culture (Day 5/6) compared with cleavage stage (Day 3) transfer, even when adjusting for confounding factors. Our findings are in agreement with the previous two studies; however, we did not show a difference in the very preterm deliveries (unlike the US study) or in fetal malformations (as in the Swedish study). We hypothesize that there may be a deleterious effect of prolonged in vitro embryo culture on subsequent placentation. Longer term follow-up studies will be required to determine if prolonged in vitro culture to the blastocyst stage has an adverse effect on the long-term health of offspring when compared with shorter cleavage stage culture.

STUDY FUNDING/COMPETING INTEREST(S)

None.

Obesity does not aggravate vitrification injury in mouse embryos: a prospective study

BACKGROUND

Obesity is associated with poor reproductive outcomes, but few reports have examined thawed embryo transfer in obese women. Many studies have shown that increased lipid accumulation aggravates vitrification injury in porcine and bovine embryos, but oocytes of these species have high lipid contents (63 ng and 161 ng, respectively). Almost nothing is known about lipids in human oocytes except that these cells are anecdotally known to be relatively lipid poor. In this regard, human oocytes are considered to be similar to those of the mouse, which contain approximately 4 ng total lipids/oocyte. To date, no available data show the impact of obesity on vitrification in mouse embryos. The aim of this study was to establish a murine model of maternal diet-induced obesity and to characterize the effect of obesity on vitrification by investigating the survival rate and embryo developmental competence after thawing.

METHODS

Prospective comparisons were performed between six-eight-cell embryos from obese and normal-weight mice and between fresh and vitrified embryos. Female C57BL/6 mice were fed standard rodent chow (normal-weight group) or a high-fat diet (obese group) for 6 weeks. The mice were mated, zygotes were collected from oviducts and cultured for 3 days, and six-eight-cell embryos were then selected to assess lipid content in fresh embryos and to evaluate differences in apoptosis, survival, and development rates in response to vitrification.

RESULTS

In fresh embryos from obese mice, the lipid content (0.044 vs 0.030, P<0.01) and apoptosis rate (15.1% vs.9.3%, P<0.05)were significantly higher, the survival rate (83.1% vs. 93.1%, P<0.01) on day 5 was significantly lower, and embryo development was notably delayed on days 3-5 compared with the normal-weight group. After vitrification, no significant difference was found between thawed embryos from obese and normal-weight mice in apoptosis, survival, and development rates on days 4 and 5. In both groups, pre- and post-vitrification embryo apoptosis, survival, and development rates were similar.

CONCLUSIONS

This study demonstrated that differences in survival and developmental rates between embryos from obese and normal-weight mice were eliminated after vitrification. Thus, maternal obesity does not aggravate vitrification injury, but obesity alone greatly impairs pre-implantation embryo survival and development.