Maternal age and risk of low birth weight and premature birth in children conceived through medically assisted reproduction. Evidence from Finnish population registers

Partnership trajectories preceding medically assisted reproduction

The number of people who undergo medically assisted reproduction (MAR) to conceive has increased considerably in recent decades. However, existing research into the demographics and the partnership histories of this growing subgroup is limited. Using unique data from Finnish population registers on nulliparous women born in Finland in 1971-77 (n = 21,129; ∼10 per cent of all women) who had undergone MAR treatment, we created longitudinal partnership histories from age 16 until first MAR treatment. We identified six typical partnership trajectories and used relative frequency sequence plots to investigate heterogeneity in partnership transitions within and between these groups. The majority of women (60.7 per cent) underwent MAR with their first partner, followed by women who underwent MAR in a second (21.5 per cent) or higher-order partnership (7.1 per cent), while 10.7 per cent underwent MAR without a partner. On average, women undergoing MAR were relatively young (with around half starting treatment before age 30) and were highly educated with high incomes.

Comparison of the perinatal outcomes of expected high ovarian response patients and normal ovarian response patients undergoing frozen-thawed embryo transfer in natural/small amount of HMG induced ovulation cycles

BACKGROUND

Due to the high risk of complications in fresh transfer cycles among expected high ovarian response patients, most choose frozen-thawed embryo transfer (FET). There are currently few researches on whether the FET outcomes of expected high ovarian response patients with regular menstrual cycles are similar to those of normal ovarian response. Therefore, our objective was to explore and compare pregnancy outcomes and maternal and neonatal outcomes of natural FET cycles between patients with expected high ovarian response and normal ovarian response with regular menstrual cycles based on the antral follicle count (AFC).

METHODS

This retrospective cohort study included 5082 women undergoing natural or small amount of HMG induced ovulation FET cycles at the Reproductive Center of the Third Affiliated Hospital of Zhengzhou University from January 1, 2017, to March 31, 2021. The population was divided into expected high ovarian response group and normal ovarian response group based on the AFC, and the differences in patient characteristics, clinical outcomes and perinatal outcomes between the two groups were compared.

RESULTS

Regarding clinical outcomes, compared with the normal ovarian response group, patients in the expected high ovarian response group had a higher clinical pregnancy rate (57.34% vs. 48.50%) and live birth rate (48.12% vs. 38.97%). There was no difference in the early miscarriage rate or twin pregnancy rate between the groups. Multivariate logistic regression analysis suggested that the clinical pregnancy rate (adjusted OR 1.190) and live birth rate (adjusted OR 1.171) of the expected high ovarian response group were higher than those of the normal ovarian response group. In terms of maternal and infant outcomes, the incidence of very preterm delivery in the normal ovarian response group was higher than that in the expected high ovarian response group (0.86% vs. 0.16%, adjusted OR 0.131), Other maternal and infant outcomes were not significantly different. After grouping by age (< 30 y, 30-34 y, 35-39 y), there was no difference in the incidence of very preterm delivery among the age subgroups.

CONCLUSION

For patients with expected high ovarian response and regular menstrual cycles undergoing natural or small amount of HMG induced ovulation FET cycles, the clinical and perinatal outcomes are reassuring. For patients undergoing natural or small amount of HMG induced ovulation FET cycles, as age increases, perinatal care should be strengthened during pregnancy to reduce the incidence of very preterm delivery.

Perinatal outcomes in 6640 singleton pregnancies after donor oocyte IVF across three continents over 7 years

PURPOSE

Are trends in singleton donor oocyte IVF perinatal outcomes consistent over time among four international ethnically diverse infertility centers?

METHODS

This retrospective cohort consisted of an infertility network of four international IVF centers across three continents. Singleton live births resulting from fresh and frozen donor oocyte embryo transfers from January 1, 2012 to December 31, 2018 were included. The main outcome measures were birth weight (BW), preterm birth (PTB), large for gestational age (LGA), small for gestational age (SGA) and gestational age (GA) at delivery.

RESULTS

The entire cohort (n = 6640) consisted of 4753 fresh and 1887 frozen donor oocyte embryo transfers. Maternal age, parity, body mass index, neonatal sex and GA at delivery were similar for fresh and frozen donor oocyte embryo transfers in the entire cohort and within each infertility center. All four centers had a trend of decreased BW and rates of PTB before 32 weeks annually, although significance was not reached. Three of the four centers had annual increased trends of PTB before 37 weeks and LGA newborns, although significance was not reached. BWs for the entire cohort for fresh and frozen donor embryo transfers were 3166 g ± 601 g and 3137 g ± 626 g, respectively.

CONCLUSION

Similar trends in perinatal outcomes were present across four international infertility centers over 7 years. The overall perinatal trends in donor oocyte IVF may be applicable to centers worldwide, but further studies in more geographic regions are needed.

Influence of maternal age on the birthweight of infants delivered from frozen-thawed blastocyst transfer cycles

The aim of this study was to investigate whether maternal age had an effect on the birthweight of singletons delivered from frozen-thawed blastocyst transfer (FBT) cycles. A total of 1203 FBT cycles occurring between July 2011 and June 2021 at a single centre were retrospectively analysed. Based on the maternal age at FBT, the patients were divided into four groups: <30, 30-34, 35-37, and ≥38 years of age. Main outcomes measured included singleton birthweights, preterm births, large-for-gestational-age (LGA) and small-for-gestational-age (SGA) live births among the groups. There was no significant difference in birth weight among the four groups, while the highest birth weight was found in the <30 years group. The incidence of very preterm births and very low birth weights demonstrated an increasing trend with age; on the contrary, the incidence of preterm births, low birth weight (LBW), high birth weight and LGA and SGA live births gradually decreased with increasing age, but these differences were not statistically significant among groups (P>0.05, respectively). Although the proportion of females was lower than that of males, the difference was not statistically significant among the groups. After adjusting for possible confounders, maternal age was found to have no effect on adverse neonatal outcomes in the regression analyses (P>0.05). Birthweight in singleton births from FBT was not affected by maternal age.

Assisted reproductive technology and neurodevelopmental outcomes in offspring: a prospective birth cohort study in East China

RESEARCH QUESTION

Is ART associated with adverse neurodevelopmental outcome in 12-month-old offspring compared with those conceived through natural conception?

DESIGN

In this prospective cohort study, 488 infertile women undergoing ART and 1397 women with natural conception were recruited and followed until their offspring were 12 months old. The primary outcome was the neurodevelopment in the offspring. The association between exposure to ART and Gesell developmental scale scores was investigated using multiple linear regression models after adjusting for confounders. Propensity score matching (PSM) and inverse probability of treatment weighting (IPTW) were used to verify the results.

RESULTS

In total, 18 (3.7%) and 40 (2.9%) children in the ART and natural conception groups, respectively, had been diagnosed with neurodevelopmental delay at 12 months of age. It was found that gross motor, adaptive behaviour, language and total development quotient scores were comparable between the groups. Following multivariate linear regression and IPTW, social behaviour development quotient scores were found to be slightly higher in the ART group than the natural conception group. Higher social behaviour development quotient scores in the ART group were also observed in the male and the singleton subgroups.

CONCLUSIONS

At 12 months, offspring born after ART appeared to have similar motor, language and adaptive behaviour skills, and total development quotient scores, to those born after natural conception. However, social behaviour development in 12-month-old infants was slightly higher in those conceived using ART than in naturally conceived offspring, especially in male or singleton infants. These findings may provide new information in evaluating the potential benefits and risks of ART.

The impact of epigenetic landscape on ovarian cells in infertile older women undergoing IVF procedures

The constant decline in fertility and older reproductive age is the major cause of low clinical pregnancy rates in industrialised countries. Epigenetic mechanisms impact on proper embryonic development in women undergoing in vitro fertilisation (IVF) protocols. Here, we describe the main epigenetic modifications that may influence female reproduction and could affect IVF success.

Risk factors associated with preterm birth in singletons born after IVF: a national cohort study

RESEARCH QUESTION

What are the risk factors for prematurity other than intrauterine growth restriction in singletons after IVF?

DESIGN

Data were collected from a national registry, based on an observational prospective cohort of 30,737 live births after assisted reproductive technology (fresh embryo transfers: n = 20,932 and frozen embryo transfer [FET] n = 9805) between 2014 and 2015. A population of not-small for gestational age singletons conceived after fresh embryo transfers and FET, and their parents, was selected. Data on a number of variables were collected, including type of infertility, number of oocytes retrieved and vanishing twins.

RESULTS

Preterm birth occurred in 7.7% (n = 1607) of fresh embryo transfers and 6.2% (n = 611) of frozen-thawed embryo transfers (P < 0.0001; adjusted odds ratio [aOR] = 1.34 [1.21-1.49]). Endometriosis and vanishing twin increased the risk of preterm birth after fresh embryo transfer (P < 0.001; aOR 1.32 and 1.78, respectively). Polycystic ovaries or more than 20 oocytes retrieved also increased preterm birth risk (aOR 1.31 and 1.30; P = 0.003 and P = 0.02, respectively); large oocyte cohort (>20) was no longer associated with the risk of prematurity in FET.

CONCLUSION

Endometriosis remains a risk for prematurity even in the absence of intrauterine growth retardation, which suggests a dysimmune effect. Large oocyte cohorts obtained by stimulation, without clinical polycystic ovary syndrome diagnosed before attempts, do not affect FET outcomes, reinforcing the idea of a phenotypic difference in the clinical presentation of polycystic ovary syndrome.

School starting age, maternal age at birth, and child outcomes

This paper analyses the effects of maternal age at birth on children's short and long-term outcomes using Finnish register data. We exploit a school starting age rule for identification. Mothers who are born after the school entry cut-off give birth at higher age, but total fertility and earnings are unaffected. Being born after the cut-off reduces gestation and, hence, child birth weight. The effects on birth weight and gestation are rather small, however, suggesting that the long-run impacts may be limited. Accordingly, we find no impacts on longer-term child outcomes, such as educational attainment and adolescent crime rates. Thus, using this source of variation, we find no favorable average effects of maternal age at birth on child outcomes.

Impact of Maternal Age on Singleton Birthweight in Frozen Embryo Transfer Cycles

BACKGROUND

Previous studies have investigated the effect of maternal age on assisted reproductive technology success rates. However, little is known about the relationship between maternal age and neonatal birthweight in frozen embryo transfer (FET) cycles. Whether maternal age influences singleton birthweight in FET cycles remains to be elucidated.

METHODS

This study was conducted at a tertiary care center, involving singleton live births born to women undergoing frozen-thawed embryo transfer during the period from January 2010 to December 2017. A total of 12,565 women who fulfilled the inclusion criteria were enrolled and grouped into four groups according to the maternal age: <30, 30-34, 35-39, and ≥40 years old. A multivariable linear regression analysis was conducted to reveal the relationship between maternal age and neonatal birthweight with controlling for a number of potential confounders.

RESULTS

The highest proportions of low birthweight (LBW, 4.1%), high birthweight (1.2%), preterm birth (PTB, 5.9%), and very PTB (0.9%) were found in the group over 40 years old, but no significant difference was observed among the four groups. Additionally, the 35-39-year-old group had the highest rate of very LBW (0.6%), whereas the 30-34-year-old group had the lowest rate of small for gestational age (SGA, 2.7%). However, multivariate analyses revealed that neonatal outcomes including PTB, LBW, and SGA were similar between the different maternal age groups.

CONCLUSION

Grouping with different maternal age was not associated with mean birthweight and Z-scores of singletons resulting from FET.

Association between paternal age and singleton birthweight in frozen embryo transfer cycles

BACKGROUND

Many studies have considered maternal age as a determinant factor for success in assisted reproductive technologies (ART), but the potential role of paternal age on neonatal outcomes has been overlooked. This study aimed to explore the association between paternal age and birthweight in frozen embryo transfer (FET) cycles.

METHODS

This retrospective study involved singleton live births born to women undergoing frozen embryo transfer from January 2013 to December 2017 at a tertiary care center in Shanghai, China. The paternal age was classified into four categories: ≤ 30, 31-35, 36-40, and ≥ 41 years. The group consisting of respondents with paternal age of 31-35 was set as the reference group. Singleton birthweight was the primary outcome measure. Z-scores were calculated according to gestational age and newborn gender on birthweight based on the national birthweight reference. Multivariable linear regression analysis was performed to reveal the relationship between paternal age and newborns' birthweight after considering several potential confounders.

RESULTS

Exactly 9765 women who fulfilled the inclusion criteria were enrolled. No significant difference was found on mean birthweight (P = 0.082) and gestation-adjusted Z-scores (P = 0.569) among paternal age categories. The reference group and the group with aged 36-40 years had the highest mean birthweight and Z-scores, respectively (3350.2 ± 467.8 g, 0.36 ± 1.00). A decline in mean birthweight with paternal age was observed, and the group over 40 years had the lowest value of 3309.4 ± 474.3 g, but the difference was not statistically significant. In multivariate analyses, the adjusted odds of very low birthweight (LBW), LBW, and high birthweight in the reference group did not significantly differ with the three other groups. After correcting several potential confounders, no significant correlation was observed between paternal age and neonatal birthweight (P = 0.289).

CONCLUSION

Paternal age was not associated with mean birthweight and gestational age- and gender-adjusted birthweight (Z-scores) of singletons among women who became pregnant in FET cycles.

Suboptimal trophectoderm mitochondrial DNA level is associated with delayed blastocyst development

PURPOSE

To provide a comprehensive analysis of mtDNA quantity in D5 and D6 blastocysts, as well as a further insight to the origin of delayed blastocyst development.

METHODS

A retrospective cohort analysis of 829 D5 and 472 D6 blastocysts from 460 patients who underwent in vitro fertilization (IVF) with next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidy (PGT-A). The quantity of trophectoderm mtDNA was extrapolated from the NGS data, followed by the analysis of mean mtDNA levels between D5 and D6 blastocysts of the same ploidy (aneuploid/euploid) and transfer outcomes (positive/negative clinical pregnancy).

RESULTS

D5 blastocysts had significantly higher euploidy rate and clinical pregnancy rate when compared with D6 blastocysts. The proportion of blastocysts derived from patients ≧ 40 years old were similar between the D5 and D6 cohorts. When blastocysts with identical ploidy were analyzed, the D5 cohorts all had significantly higher mean mtDNA levels than their D6 counterparts. Similarly, when embryo transfers with identical outcome were analyzed, the D5 cohorts also had significantly higher mean mtDNA levels than the D6 cohorts. Trophectoderm mtDNA level was independent of maternal age and blastocyst morphology grades.

CONCLUSIONS

Our data provided further evidence D5 blastocysts contained significantly greater mtDNA quantity than D6 blastocysts, and mtDNA quantity could be a key factor that affects the development rate of blastocysts. Furthermore, one must avoid using an arbitrary threshold when incorporating mtDNA quantity into the embryo selection criteria, as the observed value may have vastly different clinical implication when blastulation rate is also considered.