Modelling the potential impact of population-wide periconceptional folate/multivitamin supplementation on multiple births

Fertility treatment, twin births, and unplanned pregnancies in women with eating disorders: findings from a population-based birth cohort

Objective

To investigate fertility treatment, twin births, and unplanned pregnancies in pregnant women with eating disorders in a population-based sample.

Design

A longitudinal population-based birth cohort (Generation R).

Setting

Rotterdam, the Netherlands.

Sample

Women from the Generation R study who reported a history of (recent or past) anorexia nervosa (n = 160), bulimia nervosa (n = 265), or both (n = 130), and a history of psychiatric disorders other than eating disorders (n = 1396) were compared with women without psychiatric disorders (n = 4367).

Methods

Women were compared on the studied outcomes using logistic regression. We performed crude and adjusted analyses (adjusting for relevant confounding factors).

Main outcome measures

Fertility treatment, twin births, unplanned pregnancies, and women's feelings towards unplanned pregnancies.

Results

Relative to women without psychiatric disorders, women with bulimia nervosa had increased odds (odds ratio, OR, 2.3; 95% confidence interval, 95% CI, 1.1–5.2) of having undergone fertility treatment. Women with all eating disorders had increased odds of twin births (anorexia nervosa, OR 2.7, 95% CI 1.0–7.7; bulimia nervosa, OR 2.7, 95% CI 1.1–6.6; anorexia and bulimia nervosa, OR 3.795% CI 1.3–10.7). Anorexia nervosa was associated with increased odds of unplanned pregnancies (OR 1.8, 95% CI 1.2–2.6) and mixed feelings about these pregnancies (adjusted OR 5.0, 95% CI 1.7–14.4). Pre-pregnancy body mass index did not explain the observed associations.

Conclusions

Eating disorders are associated with increased odds of receiving fertility treatment and twin births. Women with anorexia nervosa were more likely to have an unplanned pregnancy and have mixed feelings about the unplanned pregnancy. Fertility treatment specialists should be aware that both active and past eating disorders (both anorexia nervosa and bulimia nervosa) might underlie fertility problems.

Twin Town in South Brazil: a Nazi's experiment or a genetic founder effect?

Cândido Godói (CG) is a small municipality in South Brazil with approximately 6,000 inhabitants. It is known as the “Twins' Town” due to its high rate of twin births. Recently it was claimed that such high frequency of twinning would be connected to experiments performed by the German Nazi doctor Joseph Mengele. It is known, however, that this town was founded by a small number of families and therefore a genetic founder effect may represent an alternatively explanation for the high twinning prevalence in CG. In this study, we tested specific predictions of the “Nazi's experiment” and of the “founder effect” hypotheses. We surveyed a total of 6,262 baptism records from 1959–2008 in CG catholic churches, and identified 91 twin pairs and one triplet. Contrary to the “Nazi's experiment hypothesis”, there is no spurt in twinning between the years (1964–1968) when Mengele allegedly was in CG (P = 0.482). Moreover, there is no temporal trend for a declining rate of twinning since the 1960s (P = 0.351), and no difference in twinning among CG districts considering two different periods: 1927–1958 and 1959–2008 (P = 0.638). On the other hand, the “founder effect hypothesis” is supported by an isonymy analysis that shows that women who gave birth to twins have a higher inbreeding coefficient when compared to women who never had twins (0.0148, 0.0081, respectively, P = 0.019). In summary, our results show no evidence for the “Nazi's experiment hypothesis” and strongly suggest that the “founder effect hypothesis” is a much more likely alternative for explaining the high prevalence of twinning in CG. If this hypothesis is correct, then this community represents a valuable population where genetic factors linked to twinning may be identified.

Periconceptional maternal folic acid use of 400 microg per day is related to increased methylation of the IGF2 gene in the very young child

BACKGROUND

Countries worldwide recommend women planning pregnancy to use daily 400 microg of synthetic folic acid in the periconceptional period to prevent birth defects in children. The underlying mechanisms of this preventive effect are not clear, however, epigenetic modulation of growth processes by folic acid is hypothesized. Here, we investigated whether periconceptional maternal folic acid use and markers of global DNA methylation potential (S-adenosylmethionine and S-adenosylhomocysteine blood levels) in mothers and children affect methylation of the insulin-like growth factor 2 gene differentially methylation region (IGF2 DMR) in the child. Moreover, we tested whether the methylation of the IGF2 DMR was independently associated with birth weight.

METHODOLOGY/PRINCIPAL FINDINGS

IGF2 DMR methylation in 120 children aged 17 months (SD 0.3) of whom 86 mothers had used and 34 had not used folic acid periconceptionally were studied. Methylation was measured of 5 CpG dinucleotides covering the DMR using a mass spectrometry-based method. Children of mother who used folic acid had a 4.5% higher methylation of the IGF2 DMR than children who were not exposed to folic acid (49.5% vs. 47.4%; p = 0.014). IGF2 DMR methylation of the children also was associated with the S-adenosylmethionine blood level of the mother but not of the child (+1.7% methylation per SD S-adenosylmethionine; p = 0.037). Finally, we observed an inverse independent association between IGF2 DMR methylation and birth weight (-1.7% methylation per SD birthweight; p = 0.034).

CONCLUSIONS

Periconceptional folic acid use is associated with epigenetic changes in IGF2 in the child that may affect intrauterine programming of growth and development with consequences for health and disease throughout life. These results indicate plasticity of IGF2 methylation by periconceptional folic acid use.

Folic acid and risk of twinning: a systematic review of the recent literature, July 1994 to July 2006

OBJECTIVE

To assess the evidence of an association between periconceptional folic acid (FA) supplementation or fortification of foods with FA and the risk of twinning, using the Food Standards Australia New Zealand (FSANZ) framework for assessing evidence when substantiating nutrition, health and related claims on foods.

DATA SOURCES

The Cochrane Library Database, MEDLINE, MEDLINE in Process, EMBASE, PubMed National Library of Medicine, and CINAHL were searched to identify systematic reviews and primary intervention and observational studies published from 1 July 1994 to 7 July 2006.

STUDY SELECTION

One prospective and five retrospective cohort studies that assessed the rate of twinning in populations exposed to FA through supplementation, and six retrospective registry-based cohort studies examining twinning rates after fortification of foods with FA.

DATA EXTRACTION

Two reviewers appraised eligible studies and evaluated data independently.

DATA SYNTHESIS

The best maximal risk estimates of twinning after FA supplementation were an adjusted odds ratio (adjOR) of 1.26 (95% CI, 0.91-1.73) for preconceptional supplementation and dizygotic twinning and an adjOR of 1.02 (95% CI, 0.85-1.24) for overall twinning. Data from four FA fortification studies in the United States that allowed for calculation of an annual percentage increase showed a maximal annual increase in twinning rates of 4.6%.

CONCLUSIONS

Overall, under the FSANZ framework, there is possible evidence for a relationship between periconceptional FA intake and increased twinning. To support this tentative relationship, more well designed, long-term follow-up studies are needed in places where fortification with FA has been introduced, focusing on dose-response and obtaining accurate data on infertility treatments.

Vitamin supplementation for preventing miscarriage

BACKGROUND

Miscarriage is a common complication of pregnancy that can be caused by a wide range of factors. Poor dietary intake of vitamins has been associated with an increased risk of miscarriage, therefore supplementing women with vitamins either prior to or in early pregnancy may help prevent miscarriage.

OBJECTIVES

The objectives of this review are to determine the effectiveness and safety of any vitamin supplementation, on the risk of spontaneous miscarriage, maternal adverse outcomes and fetal and infant adverse outcomes.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (8 September 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2003) and MEDLINE (1966 to May 2003), Current Contents (1998 to May 2003) and EMBASE (1980 to May 2003).

SELECTION CRITERIA

All randomised and quasi-randomised trials comparing one or more vitamins with either placebo, other vitamins, no vitamins or other interventions, prior to conception, periconceptionally or in early pregnancy (less than 20 weeks' gestation).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, extracted data and assessed trial quality.

MAIN RESULTS

We identified seventeen trials assessing supplementation with any vitamin(s) starting prior to 20 weeks' gestation and reporting at least one primary outcome that were eligible for the review. Overall, the included trials involved 35,812 women and 37,353 pregnancies. Two trials were cluster randomised and contributed data for 20,758 women and 22,299 pregnancies in total. No difference was seen between women taking any vitamins compared with controls for total fetal loss (relative risk (RR) 1.05, 95% confidence interval (CI) 0.95 to 1.15), early or late miscarriage (RR 1.08, 95% CI 0.95 to 1.24) or stillbirth (RR 0.85, 95% CI 0.63 to 1.14) and most of the other primary outcomes, using fixed-effect models. For the other primary outcomes, women given any type of vitamin(s) compared with controls were less likely to develop pre-eclampsia (RR 0.68, 95% CI 0.54 to 0.85, four trials, 5580 women) and more likely to have a multiple pregnancy (RR 1.38, 95% CI 1.12 to 1.70, three trials, 20,986 women).

AUTHORS' CONCLUSIONS

Taking vitamin supplements, alone or in combination with other vitamins, prior to pregnancy or in early pregnancy, does not prevent women experiencing miscarriage or stillbirth. However, women taking vitamin supplements may be less likely to develop pre-eclampsia and more likely to have a multiple pregnancy.

Impact of misclassification of in vitro fertilisation in studies of folic acid and twinning: modelling using population based Swedish vital records

OBJECTIVE

To determine whether failure to adequately adjust for a reported 40% misclassification of use of in vitro fertilisation (IVF) as reported in a Swedish study could have led to a false finding that folic acid increases dizygotic twinning.

DESIGN

Modelling with population based data.

SETTING

Swedish vital records for 1995-9.

MAIN OUTCOME MEASURES

Rates of twinning calculated according to whether women used IVF to become pregnant. Estimated unadjusted and adjusted odds ratios of the association between use of folic acid and twinning by use of IVF.

RESULTS

In 1995-9, Swedish women who used IVF had an almost 20 times the chance of having twins than women who did not use IVF (rate ratio 19.7, 95% confidence interval 18.7 to 20.6). In the absence of a true effect of folic acid, the use of a 40% misclassified surrogate variable to adjust for use of IVF would have resulted in a false finding that folic acid was associated with a more than twofold increase in twinning.

CONCLUSION

Use of IVF is a strong confounder because it is associated with both use of folic acid and twinning. Even when misclassification of IVF was reduced to 5%, this bias persisted in the adjusted model. Using a 40% misclassified surrogate to adjust for IVF, as reported in the Swedish study, probably led to a false finding that folic acid increased dizygotic twinning.

Trends in the occurrence, determinants, and consequences of multiple births

After a substantial decrease in the middle of the 20th century, multiple pregnancy rates have increased in many Western countries. Between the mid-1970s and 1998, the rate of twin pregnancies increased by 50% to 60% in England and Wales, France, and the United States. The rates of triplet or higher-order multiple pregnancies increased by 310% in France, 430% in England and Wales, and 696% in the United States. One fourth to one third of the increase in twin or triplet pregnancies are attributable to a contemporaneous increase in maternal age. Furthermore, in countries with high occurrence of multiple births, 30% to 50% of twin pregnancies and at least 75% of triplet pregnancies occur after infertility treatment. The impact of the increase in multiple births on preterm delivery rates in the overall population is mainly attributable to twin pregnancies. In Canada, France, and the United States, an increase in preterm births among multiples contributed almost as much as the increase in occurrence of multiple births to the increase or stabilization of the overall rates of preterm delivery observed in these countries.