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A systematic review and meta-analysis suggests that in pregnancies conceived via assisted reproduction, risk of adverse perinatal outcomes may be higher with donated than with autologous oocytes. Plus: Do post-cesarean antibiotics reduce infections in obese women? Also: Researchers believe they have identified the genes associated with preterm delivery.
A systematic review and meta-analysis suggests that in pregnancies conceived via assisted reproduction, risk of adverse perinatal outcomes may be higher with donated than with autologous oocytes. The findings, by researchers from the UK and India, were published in the European Journal of Obstetrics & Gynecology and Reproductive Biology.
For the research, the authors performed a systematic literature search for studies in English published between 1980 and 2016 that compared perinatal outcomes of pregnancies following in vitro fertilization (IVF) with fresh or frozen donated or autologous oocytes. Using Cochrane Collaboration software, meta-analysis was done for preterm birth (PTB) (< 37 weeks), early PTB (< 32 weeks), low birthweight (LBW) (< 2500 g), very LBW (< 1500 g) and small-for-gestational-age (SGA) (< 10th percentile. There were 6 studies on PTB, 3 on early PTB, 5 on LBW, 4 on very LBW, and 3 studies on SGA after fresh embryo transfer. Data on frozen embryo transfer were from 2 studies on PTB, early PTB, LBW, and very LBW.
The analysis showed a higher risk of PTB after fresh embryo transfer in pregnancies using donated oocytes than in pregnancies created through IVF with autologous oocytes (OR 1.45, 95% CI 1.20-1.77). Assuming that PTB risk is 9% for pregnancies after IVF with autologous oocytes, that translates to a PTB risk between 10.8% and 15.9% for pregnancies using oocyte donation. A similar increase in risk with donated oocytes was seen for LBW (OR 1.34, 95% CI 1.12-1.60). If the assumed risk of LBW is 9% for IVF with autologous oocytes, then donated oocytes are associated with an LBW risk of 10.1% to 14.4%. The same relationship was seen for early PTB (OR 2.14, 95% CI 1.40-3.25) and very LBW (OR 1.51, 95% CI 1.17-1.95).
Do post-cesarean antibiotics reduce infections in obese women?
A study published in JAMA suggests that a postoperative 48-hour course of antibiotics significantly decreased the rate of surgical site infection (SSI) within 30 days after delivery in obese women undergoing cesarean delivery. The randomized, double-blind clinical trial compared oral cephalexin and metronidazole versus placebo.
From October 2010 through December 2015, 403 participants (mean age, 28; mean BMI, 39.7) were randomly assigned to receive oral cephalexin 500 mg and metronidazole 500 mg (n=202 participants) or an identical-appearing placebo (n=201 participants) every 8 hours for 48 hours after cesarean delivery. Of the 403 participants, 382 (94.6% completed the trial). The overall rate of SSI was 10.9% and the infections were diagnosed in 13 women among the cephalexin-metronidazole group (6.4%) and in 31 women in the placebo group (15.4%). No serious adverse events were seen in either group.
While giving obese women a postoperative course of oral antibiotics seemed to reduce the risk of SSI, the authors noted a few limitations to the study. The trial was performed at a single site (University of Cincinnati Medical Center) with a high prevalence of obesity, and the findings may not translate to all obstetric practices. In addition, more research is necessary to determine if there is a subpopulation in this group to which the benefit would be limited so that unnecessary exposure to antibiotics can be avoided.
Study identifies genes associated with preterm delivery
Genes that regulate gestational length and affect likelihood of preterm delivery have been identified, according to a study published in the New England Journal of Medicine. Researchers performed a two-stage genome-wide association study to identify and replicate genetic loci associated with preterm delivery and gestational duration. The study involved more than 50,000 women, primarily of European ancestry.
The researchers obtained data from participants in the research program 23andMe, a personal genetics company that provides users with information about their geographical genetic make-up through user-submitted saliva samples. Women with more than 97% European ancestry and who self-reported the gestational duration of their first live singleton birth were included in the study. A reference group of 8,643 women in Denmark, Finland and Norway was used to test for replication.
Linear regression was used to test single-marker genetic associations with gestational duration and logistic regression was used to test these associations with preterm birth (PTB). The authors clustered single-nucleotide polymorphisms (SNPs) into association regions (loci) by first identifying SNPs with an association of P < 1.0x10-4 and grouping these SNPs into a region if they were adjacent to each other. The index SNP was the one with the smallest P value within each region. In the replication stage, regions with a suggestive significance of P < 1.0x10-6 were tested.
The study shows that of the 12 maternal genetic loci identified with a suggestive significance, there are four genes that show a clear link to gestation length: EBF1, EEFSEC, AGTR2, and WNT4. Common variants of the first three genes also appeared to have a determining influence on the likelihood of PTB. Variants of two other genes, ADCY5 and RAPC2, could also affect gestation length, but that was most evident in the reference group.
The authors note that while these results are significant, there were some limitations to the study and more follow-up is necessary. The fact that data were self-reported make them difficult to verify, though one study mentioned in the research shows that approximately 90% of the gestational durations that were self-reported agreed with the mother’s associated medical records. In addition, the researchers were unable to distinguish medically indicated births and spontaneous births among the mothers who carried to term. Lastly, the study was limited to participants of European ancestry, so it is unknown if the same loci are involved in the pregnancies of women with non-European ancestry.